LISFLOOD-FP User Manual

LISFLOOD-FP User Manual
LISFLOOD-FP
User manual
Code release 5.9.6
Paul Bates, Mark Trigg, Jeff Neal and Amy Dabrowa
School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1SS, UK.
25th November 2013
LISFLOOD-FP User Manual
Code release 5.9.6
Document information
Project title
Document title
Code release
Prepared by
Checked by
Code contributions
Document version
Issue date and time
Original file stored at
LISFLOOD-FP shareware version
LISFLOOD-FP User Manual
5.9.6
Paul Bates, Amy Dabrowa, Tim Fewtrell, Jeff Neal and Mark
Trigg
Amy Dabrowa
Paul Bates, Matt Horritt, Matt Wilson, Neil Hunter, Tim
Fewtrell, Mark Trigg and Jeff Neal, Gustavo de Almeida,
Chris Sampson
2.0
25/11/2013
https://svn.ggy.bris.ac.uk/subversion/lisflood/
(password protected)
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Code release 5.9.6
Disclaimer
Before using the LISFLOOD-FP software (hereafter “the Software”) please read carefully the
following terms for use. Extracting files from the LISFLOOD-FP.zip archive on to your computer
indicates you accept the following terms.
1. The University of Bristol (hereafter “the Developers”) do not warrant that the software will
meet your requirements or that the operation of the software will be uninterrupted or error-free
or that all errors in the Software can be corrected.
2. You install and use the Software at your own risk and in no event will the Developers be liable
for any loss or damage of any kind including lost profits or any indirect incidental or other
consequential loss arising from the use or inability to use the Software or from errors or
deficiencies in it whether caused by negligence or otherwise.
3. The Developers accept no responsibility for the accuracy of the results obtained from the use
of the Software. In using the software you are expected to make final evaluation in the
context of your own problems.
4. Users are not in reliance on any statements warranties or representations which may have
been made by the Developers or by anyone acting or purporting to act on their behalf.
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Executive summary
This document is the user manual for the shareware implementation of the LISFLOOD-FP raster
flood inundation model version 5.9.5. The code provides a general tool for simulating fluvial or
coastal flood spreading, with output consisting of raster maps of values for a number of flood
water parameters such as depth, water surface elevation, velocity etc. in each grid square at each
time step. In the case of fluvial flooding it also outputs predicted stage and discharge
hydrographs at the outlet of the reach and other specified locations. For fluvial situations, this
version of LISFLOOD-FP solves the kinematic or diffusive approximations to the one-dimensional
St. Venant equations to simulate the passage of a flood wave along a channel reach. Once
bankfull depth is exceeded, water moves from the channel to adjacent floodplains sections where
two dimensional flood spreading is simulated using a storage cell concept applied over a raster
grid. There are three options for calculation of water flow between cells in the raster grid which
vary in their physical complexity. In the simplest case the model assumes that flood spreading
over low-lying topography is a function of gravity and topography, whilst the most complex case
uses the full shallow water equation. Channels can also be represented as features within the 2D
grid structure using a subgrid version of the model. This calculates the combined flow of water
within each cell, contained both within any section of channel located in that cell and across the
adjacent floodplain, using an approximation to the one-dimensional St. Vernant equation without
advection. The model is designed to take advantage of recent developments in the remote
sensing of topography such as airborne laser altimetry or airborne Synthetic Aperture Radar
interferometry which are now beginning to yield dense and accurate digital elevation models over
wide areas.
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Major Version History
Ver
Date
Details
----
-------
----------------------------------------------------------------------------------------------------
5.9
Aug 05 2013 Support for LatLong added (Chris Sampson)
5.8
Feb 15 2013
5.7
Sep 26 2012 Fully tested and bug fixed bridge implementation in subgrid (Mark Trigg)
5.6
Aug 06 2012 Alternative sub-grid channel geometries added (Jeff Neal)
5.5
Jun 27 2012
5.4
Regression model wetted perimeter added, bug fix for SGC wider than cell
(Jeff Neal)
2D version of friction (x-y coupled) implemented. Old (1D) version still
available using the "1Dfriction" keyword in the .par file (Gustavo A.M. de
Almeida)
Mar 21 2012 Rainfall routing added to allow rainfall to be simulated over complex terrain
(Chris Sampson)
5.3
Sep 26 2011
q-centered numerical scheme implemented and tested for the solution of the
simplified St. Venant equation. (Gustavo A.M. de Almeida)
5.2
Jul 22 2011
Weir flows implemented in sub-grid channel and floodplain models (Jeff
Neal)
5.1
May 31 2011 Initial sub-grid channel implementation
5.0 Jan 21 2011
Fully functional Roe solver (Jeff Neal and Ignacio Villanueva) and multiple
river capability (Chris Sampson) added
4.4
Feb 01 2010 Tested version of Roe solver. 2D only, point source closed boundary only
added (Jeff Neal and Ignacio Villanueva)
4.3
Sep 04 2009 Dynamic & diffusive steady state 1D solution added & tested (Tim Fewtrell)
4.1
Nov 10 2008 TRENT solver added but not tested. Integrated version tested (Jeff Neal and
Ignacio Villanueva)
3.6
Jul 31 2008
3.5
Jun 13 2008 OpenMP version implemented and tested on Buscot (Jeff Neal)
3.4
Apr 21 2008 Double precision version (Mark Trigg)
3.3
Jan 11 2008 Diffusive channel solver & Bug fixed branching channels (Mark Trigg)
3.1
Oct 08 2007 Fully tested and bug fixed modular code (Mark Trigg)
3.0
May 25 2006 Modularised the code and added porosity scaling algorithm (Tim Fewtrell)
2.7
Feb 25 2005 Evaporation and Infiltration added (Matt Wilson)
2.6
Dec 20 2004 Added more output file and command line options (Matt Wilson)
2.5
Nov 25 2004 Checkpointing functionality added (Matt Wilson)
2.0
Jun 08 2004 Adaptive timestep implemented (Neil Hunter)
1.0
2003
First public release version (Matt Horritt)
0.9
2003
Increased output file and command line options (Matt Wilson)
0.8
2001
Prototype C++ version created (Matt Horritt)
0.5
2001
Original version created by Paul Bates and Ad De Roo
Decouple river channel timestep from floodplain timestep (Mark Trigg)
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Contents
DOCUMENT INFORMATION
2
DISCLAIMER
3
EXECUTIVE SUMMARY
4
MAJOR VERSION HISTORY
5
CONTENTS
6
LIST OF TABLES
9
1
INTRODUCTION
10
1.1
Overview
10
1.2
Floodplain flow solvers
11
1.3
Channel flow solvers
12
1.4
Model assumptions and key limitations
1.4.1
Channel flow solvers
1.4.2
Floodplain flow solvers
12
12
12
2
FILES DOWNLOADED IN ZIP ARCHIVE
13
3
DATA REQUIREMENTS, INPUT FILES AND FILE FORMATS 14
3.1
Data requirements
14
3.2
Input file formats
3.2.1
Parameter file (.par)
3.2.2
Channel information file (.river)
3.2.3
Multiple unconnected channels (.rivers)
3.2.4
Boundary condition type file (.bci)
3.2.5
Time varying boundary conditions file (.bdy)
3.2.6
Digital Elevation Model file (.dem.ascii)
3.2.7
Porosity file
3.2.8
Floodplain friction coefficient file (.n.ascii)
3.2.9
Sub-grid model river width file (.width.asc)
3.2.10
Sub-grid model bed elevations file (.bed.asc) (optional)
3.2.11
Sub-grid model bank elevation file (.bank.asc)
3.2.12
Sub-grid model channel region file (.region.asc) (optional)
3.2.13
Sub-grid model channel parameter file (.pram) (optional)
3.2.14
Weir & bridge cell linkage specification file (.weir)
6
15
15
22
25
25
26
26
27
27
27
27
27
28
28
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3.2.14.1 Weirs, embankments and structures
3.2.14.2 Bridges (currently subgrid channel version only)
3.2.15
Multiple overpass file (.opts)
3.2.16
Stage output data file (.stage)
3.2.17
Evaporation data file (.evap)
3.2.18
Alternative ascii header file (.head)
3.2.19
Virtual gauge output data file (.gauge)
3.2.20
Rainfall data file (.rain)
3.2.21
Checkpointing file (.chkpnt)
3.2.22
Start file – water depth (.start)
3.2.23
Start file – water depth binary (.startb)
3.2.24
Startfile – water elevation
29
29
30
30
30
31
31
31
32
32
32
32
4
SETTING UP A SIMULATION
32
5
RUNNING A SIMULATION
33
5.1
Checkpointing
35
5.2
Output file formats
36
5.2.1
Mass balance output file (.mass)
36
5.2.2
Water depths and elevations at time of satellite overpass (.op and .opelev) 36
5.2.3
Channel water surface profile (.profile)
36
5.2.4
Synoptic water depth, water surface elevation files (-xxxx.wd, -xxxx.elev and –
xxxx.wdfp)
37
5.2.5
Maximum water surface elevation file (.mxe) and maximum water depth (.max) 37
5.2.6
Time of initial inundation (.inittm), time of maximum depth (.maxtm) and total time
of inundation (.totaltm)
37
5.2.7
Discharge and velocity values (-xxxx.Qx, -xxxx.Qy, -xxxx.Qcx, -xxxx.Qcy,
-xxxx.Vx and –xxxx.Vy)
37
5.2.8
Hazard output files (.maxVx, .maxVy, .maxVc, .maxVcd and .maxHaz)
38
5.2.9
Adaptive time step and flow limiter (-xxxx.QLx and -xxxx.QLy) values
38
5.2.10
Stage values (.stage)
38
5.2.11
Debugging files for interpolating channels onto the DEMfile, modified dem
(*.dem), channel mask (*.chmask) and channel segment mask (*.segmask).
38
5.2.12
Debugging files produced when using subgrid channels (*.dem, *_SGC_bedZ.asc,
*_SGC_bfdepth.asc and *_SGC_width.asc).
39
5.2.13
Discharge file (*.discharge)
39
5.3
6
Visualising model results
39
APPENDIX
40
6.1
Weir calculations
40
6.2
Bridge calculations
40
7
REFERENCES AND BIBLIOGRAPHY
7
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Code release 5.9.6
LIST OF FIGURES
Figure 1: Bridge as implemented in lisflood-fp. ........................................................................... 41
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List of Tables
Table 1 Solvers available for calculating floodplain flow ............................................................. 10
Table 2 Solvers available for calculating channel flow ............................................................... 10
Table 3 Files deployed from the LISFLOOD-FP.zip archive. ...................................................... 13
Table 4: Input data required by the LISFLOOD-FP model. ......................................................... 14
Table 5 Basic and commonly used parameters, setting and input files ....................................... 15
Table 6 Items that turn on or off specific model solvers. If none of these items are entered
then the 1D kinematic solver will be used to river channel flow and the 2D
adaptive solver will be used for floodplain flow ............................................................. 16
Table 7 Defining river channel location and properties ............................................................... 17
Table 8 Defining additional water inputs and outputs (rainfall, evaporation and infiltration) ......... 17
Table 9 Options relating specifically to model starting conditions................................................ 18
Table 10 Additional, less commonly used settings and parameters ............................................ 18
Table 11 Options related to additional output files or output settings .......................................... 20
Table 12: Types of boundary condition available in the .bci file................................................ 25
Table 13: Simple shapes of sub-grid channels ........................................................................... 28
Table 14: Command line options for LISFLOOD-FP. .................................................................. 33
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1 Introduction
1.1 Overview
This document describes the flood inundation model LISFLOOD-FP. LISFLOOD-FP is a rasterbased flood inundation model designed for research purposes by the University of Bristol. The
model includes a number of numerical schemes (solvers) that simulate the propagation of flood
waves along channels and across floodplains using simplifications of the shallow water equations.
The choice of numerical scheme will depend on the characteristics of the system to be modelled,
requirements on time of execution and the type of data available. The momentum and continuity
equations for the 1D full shallow water equations are given below (equations (1) and (2)
respectively):
(1)
(2)
where Qx is volumetric flow rate in the x Cartesian direction, A the cross sectional area of flow, h
the water depth, z the bed elevation, g gravity, n the Manning’s coefficient of friction, R the
hydraulic radius, t time and x the distance in the x Cartesian direction. The tables below
summarise the key inclusions/exclusions of the solvers available for both floodplain and channel
flow. The solvers are described qualitatively in the following sections. However, it is highly
recommended that users read the references provided in Table 1 and Table 2 which provide a
thorough technical description of the solvers including their governing equations and various
validation test cases.
Table 1 Solvers available for calculating floodplain flow
Solver
Dimensions
Routing
1D on 2D grid
Flow-limited
1D on 2D grid
Shallow water terms
included
User specified velocity and
bed slope direction only
Friction and water slopes
Shallow water terms
assumed negligible
All
Time
step
Adaptive
Fixed
As above
Friction and water slopes,
local acceleration
Local and convective
acceleration
As above
Convective
acceleration
All terms
None
Adaptive
Further technical
details
Sampson et al.,
2012
Bates and De Roo,
2000
Hunter et al., 2005
Bates et al., 2010;
De Almeida et al.,
2012
Neal et al., 2012b;
Adaptive
Acceleration
1D on 2D grid
1D on 2D grid,
friction terms in 2D
Roe
2D
Time
step
Linked
to
2D
Further technical
details
Bates and De Roo,
2000
Adaptive
Adaptive
Table 2 Solvers available for calculating channel flow
Solver
Dimensions
Kinematic
1D
Shallow water terms
included
Friction slope and water
slope
including
bed
10
Shallow water terms
assumed negligible
Local and convective
acceleration,
free
LISFLOOD-FP User Manual
Diffusive
1D
Sub-grid
channel
1D
Code release 5.9.6
gradient (dz/dx) only
surface
(dh/dx)
Friction slope and water
slope including bed and
free surface gradients
(d[z+h]/dx)
Friction and water slopes,
local acceleration
Local and convective
acceleration
Convective
acceleration
gradient
solver
used or
fixed
As
above
Adaptive
Trigg et al., 2009
Neal et al. 2012a
1.2 Floodplain flow solvers
The simplest method employed to move water between cells is via the “routing” solver. If
implemented it is applied only to cells containing either very shallow water (<1 mm as default or
user defined) or where water slopes are very high (>1 in 10 or user defined). It replaces the
shallow water equations in cells with water depths below or water slopes above a user defined
threshold. Water flows with a fixed flow velocity from the specified cell into whichever
neighbouring cell has the lowest elevation (assuming it is lower than the current cell) as
determined by an pre-calculated flow direction map that is generated automatically. This solver
has the effect of reducing model runtime and allowing water to flow over terrain discontinuities
(such as off building roofs) without destabilising the solution. For deeper, low gradient flows the
acceleration model scheme is used for the flow calculation.
The least complex solver based on the shallow water equations is referred to as the “flow
limited” model. This uses an approximation of the diffusion wave equations based on the
Manning’s equation. It calculates flow between cells during a time step as a function of the free
surface and bed gradients (the water slope) and the friction slope. Both local and convective
acceleration terms are assumed negligible. This solver employs a user defined time step which is
of fixed duration for the whole simulation. However, unless this time step is very small it may be
long enough for all the water to drain from one cell to the next over a single time step, leading to
flow in the opposite direction during the next time step and model instability. To overcome this
problem a “flow limiter” was introduced setting a limit on the volume of water allowed to flow
between cells during a single time step, as a function of flow depth, grid size and time step. This
fixed time step, flux-limited scheme is rarely used due to its poor accuracy.
The “adaptive” model is a one-dimensional approximation of a diffusion wave based on uniform
flow formula, which is decoupled in x and y directions to allow simulation of 2D flows. It differs
from the flow limited solver by having a time step which varies in duration throughout the
simulation rather than one with a fixed duration. This overcomes the problem of cells emptying
during a time step without the need of a flow limiter, however the stable time step scales with
(1/∆x)2, where ∆x is the cell size, and can lead to a large increase in computation time at finer grid
resolutions. This solver is rarely used for high resolution simulation.
The “acceleration” model is a simplified form of the shallow water equations, where only the
convective acceleration term is assumed negligible. Flows between cells are calculated as a
function of the friction and water slopes, and local water acceleration. The method is first-order in
space and explicit in time, but uses a semi-implicit treatment for the friction term to aid stability.
Like the adaptive solver, the time step used by the acceleration solver varies throughout the
simulation. In this case it varies according to the Courant-Friedrichs-Lewy condition and is related
to the cell size and water depth. The stable time step scales with 1/∆t, and therefore even though
it is more complex than the adaptive formulation it can significantly decrease computation time
compared with the adaptive solver.
Finally, the “Roe” solver includes all of the terms in the full shallow water equations. The method
is based on the Godunov approach and uses an approximate Riemann solver by Roe based on
the TRENT model presented in Villanueva and Wright (2006). The explicit discretisation is firstorder in space on a raster grid. It solves the full shallow water equations with a shock capturing
scheme. LISFLOOD-Roe uses a point-wise friction based on the Manning´s equation, while the
domain boundary/internal boundary (wall) uses the ghost cell approach. The stability of this
approach is approximated by the CFL condition for shallow water models. Note: this solver has
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thus far only been tested on a limited number of scenarios and may not be as robust as the other
more commonly used solvers.
1.3 Channel flow solvers
The most simple of the channel flow models is a 1D kinematic wave approximation of the shallow
water equations, which assumes all terms except the friction and bed gradient are negligible
(“kinematic” solver). The bed gradient is a simplification of the water slope term which takes into
account the effect of changes in bed height with distance, but not changes in the water free
surface height. In contrast, the “diffusive” solver uses the 1D diffusive wave equation which
includes the water slope term and thus is able to predict backwater effects. Using the 1D channel
solvers, once channel water depth reaches bankfull height, water is routed onto adjacent
floodplain cells to be distributed as per the chosen floodplain solver. Note: there is no transfer of
momentum between the channel and floodplain, only mass.
The most recently developed method for representing rivers is as sub-grid channels, embedded
with the 2D domain. Flow between channel segments is calculated based on the friction and
water slopes, and local water acceleration (i.e. using the ‘acceleration’ model equations). Only
convective acceleration is assumed negligible. For any cell containing a sub-grid channel
segment, the solver calculates the combined flow of water within the cell, contained both within
the channel located in that cell and across the adjacent floodplain. The model is designed to
operate over large data sparse areas where limited channel section data are available.
1.4 Model assumptions and key limitations
The code is limited to situations where there is sufficient information to accurately
characterise the model boundary conditions, specifically mass flux with time at all inflow
points. In addition, for fluvial flows at least some basic information on channel geometry
must also be available.
The model uses standard SI units for length (metres), time (seconds), flux (volume per time in
m3s-1) etc.
The solvers assume flow to be gradually varied (the routing solver is the exception for this
and can be used for cases of very shallow flow over steeps gradients or discontinuities, the
Roe solver may also handle flows that vary rapidly in time).
1.4.1 Channel flow solvers
The 1D kinematic and diffusive solvers assume that the in-channel flow component can be
represented using a kinematic or diffusive 1D wave equation with the channel geometry
simplified to a rectangle (1D kinematic and diffusive solvers only).
The 1D kinematic and diffusive solvers assume the channel to be wide and shallow, so the
wetted perimeter is approximated by the channel width such that lateral friction is neglected.
1.4.2 Floodplain flow solvers
For out-of-bank flow we assume that flow can be treated using a series of storage cells
discretised as a raster grid with flow in Cartesian coordinate directions only.
There is no exchange of momentum between 1D channel solvers and floodplain flows, only
mass.
During floodplain flow lateral friction is assumed negligible and is neglected.
The flow limited solver underestimates wave propagation speeds and can be a poor
representation of flow dynamics, and is left as an option for comparative experimentation
only.
Due to high computation cost the adaptive solver is rarely suitable for high resolution
simulations.
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Wave propagation speed can be underestimated during flows in extremely low Manning’s
friction conditions and/or relatively high Froude number by all solvers except Roe (see de
Almeida and Bates 2013 for further details).
Using the acceleration solver, low Manning’s friction conditions can cause instabilities and a
numerical diffusion term must be included.
The routing solver assumes that flow between cells occurs at a constant speed and that flow
direction is controlled purely by DEM elevation. However, it also assumes that water will not
flow between cells when the water elevation in the recipient cell is greater than the DEM
elevation in the source cell.
The routing solver assumes no knowledge of roof level drainage structures
Using the routing solver, instabilities can occur if depththresh is set to greater than 10 mm
(though this condition shouldn’t generally be required even during extreme rainfall events)
Please see also the limitations for bridge and weir flow in the appendix if you intend to use these
options.
2 Files downloaded in zip archive
The model files are provided as a WinZip archive LISFLOOD-FP.zip which should first be
unpacked into a suitable directory using the WinZip shareware programme. A total of 14 files are
deployed from the archive as follows (Table 3):
Table 3 Files deployed from the LISFLOOD-FP.zip archive.
File name
Description
LISFLOOD-WIN.EXE
Pre-compiled executable for use on Windows systems (provided for 32 and 64 bit
systems
LISFLOOD_MACOSX.EXE
Pre-compiled executable for use on Mac systems (compiled on an OS X v 10.9 machine)
LISFLOOD-LIN.EXE
Pre-compiled executable for use on Linux systems
DLL FILE
Library file, Windows only. Newer systems may not need this and it is preferable not to
use it. Check first whether lisflood will run without this file present in the folder
BUSCOT_D.PAR
Example input file containing model parameters and options using the diffusive 1D solver
for channel flow
BUSCOT.WEIR
Example input file detailing location and nature of weir linkages between storage cells
BUSCOT_D.RIVER
Example input file detailing river location and geometry for 1D in-channel calculations
using the diffusive 1D solver
BUSCOT.N.ASCII
Example raster grid of floodplain friction coefficient values in ARC ascii format
BUSCOT.DEM.ASCII
Example raster grid of floodplain elevation heights in ARC ascii format
BUSCOT.BDY
Example input file for time varying boundary conditions
BUSCOT.BCI
Example input file identifying boundary condition types
BUSCOT.OPTS
Example file giving times of satellite overpasses
FLOODVIEW.EXE
Results viewer for Windows PC systems
These are the model executables, a viewer for LISFLOOD-FP results for Windows PC systems
(FloodView, see section 5.3 for further details) and all the files necessary to run a single example
application, in this case for a 3 km reach of the River Thames downstream of Buscot weir.
Once deployed from the archive the files require no further installation. Note: the model is run
from the command line, not by double clicking the executable (see section 5 for further
details).
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3 Data requirements, input files and file formats
3.1 Data requirements
Model data requirements are outlined in Table 4.
Table 4: Input data required by the LISFLOOD-FP model.
Data requirement
Source
Comments
Raster Digital Elevation Model.
Typically
derived
from
air
photogrammetry or airborne laser
altimetry (LiDAR).
Grid resolutions of approximately 25100m would seem appropriate for most
rural floodplain applications, although
smaller resolutions are preferable in urban
areas. Vertical accuracy of the DEM
should generally be less than 0.25 m.
Experience has shown the coarse
resolution
models (250-500m) can
produce
good
inundation
extent
predictions for rural floodplains if the
predicted water levels are projected back
on to the high resolution DEM.
Inflow discharge hydrograph.
Gauging station records.
Flow
enters the model through the
upstream channel cell forming the
first location on each river channel
vector in the .river file.
Model can be used in either steady state
or dynamic modes, but flows should be
accurate to
10 %.
For dynamic
simulations, temporal resolution depends
on the speed of the hydrograph rise but
typically at least hourly data are required.
Flow across the domain edge
Can be based on gauging station
records, spot water elevation or flux
measurements, tidal curve or
tide/flood frequency data. Defined in
the .bci file.
Can be used to provide a downstream
boundary condition for floodplain flows or
simulate tidal forcing for coastal flooding
applications.
Point sources within the domain
Can be based on gauging station
records, spot water elevation or flux
measurements, tidal curve or
tide/flood frequency data. Defined in
the .bci file.
Used to specify point source discharges
or flow over defences within the domain.
Can be used to avoid simulating flow in
offshore areas in coastal applications (e.g.
Bates et al., 2005).
Channel slope.
Taken from the DEM or surveyed
cross sections.
Can be set individually for each point on
the channel vector if necessary.
Channel width.
Taken from the DEM or surveyed
cross sections.
Can be set individually for each point on
the channel vector if necessary. Need not
be the same as the model grid resolution
Bankfull depth.
Taken from the DEM or surveyed
cross sections.
Can be set individually for each point on
the channel vector if necessary.
Channel and floodplain friction.
User defined parameters typically
chosen with reference to published
tables such as those given by Chow
(1959) or Acrement and Schneider
(1984).
Nc typically between 0.01 and 0.05
Nfp typically between 0.03 and 0.15
Can be set individually for each grid cell if
necessary.
User defined. An explicit numerical
scheme is used so the stability is a
function of the cell dimensions and
the flow rate. As water enters the
model via a single inflow cell at the
head of the reach, flow rates in this
Varies between applications but typical
values are in the range 2-20 s.
Boundary conditions.
These can be specified in a number
of ways:
Channel geometry
Model time step
Fixed time step version
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cell are usually the limiting factor.
Adaptive time step versions
Optimum time step to maintain
stability is calculated by the code
Calculated by the code. Optimum time
step reduces quadratically with grid size
with the ‘adaptive’ model and linearly with
the ‘acceleration’ model. May result in
substantial increase in computational cost
for fine grids
These data are then input into the model using the input files described in section 3.2.
3.2 Input file formats
Data is input to the model using seventeen file types as described below. Users should note that
the file extensions are not mandatory, comments can only be used in the parameter file (.par)
and all items are case sensitive.
3.2.1 Parameter file (.par)
This file contains the information necessary to run the simulation including file names and
locations and the main model and run control parameters. The following general principles apply:
All items in the file are case sensitive.
Items not recognised are ignored rather than generating an error message.
The code expects one item per line only.
If a keyword does not appear the model uses the default value specified in the code and
(usually) does not generate an error message.
The order given below is not fixed.
To comment out a line place a # in the first character space.
The following tables list keywords that are specified in the parameter file. These define parameter
values, tell the model to read in specified files, turn model options on and off or tell the model to
output specific files. Where a keyword should be followed by further information input by the user
this is indicated in the first column of the table. Keywords have been separated into those which
are most commonly used (Table 5), those which specify which solver should be used (Table 6),
those which relate to river and other water inputs (Table 7 and Table 8 respectively), those
relating to starting conditions (Table 9), additional less commonly used options and parameters
(Table 10) and output files (Table 11).
Table 5 Basic and commonly used parameters, setting and input files
Item name input
Description
Value in the Buscot
weir
test
case
(Diffusive case)
Applicable
model solver
DEMfile filename
Digital Elevation Model file name
No default,
Buscot.dem.ascii
All solvers
resroot name
Root for naming of results files (e.g. root.op,
root.mass, root-0001.wd etc)
Default: out
Buscot:
res_D
(giving
res_D.op,
res_D.mass etc),
All models
dirroot foldername
Relative or absolute path for the directory where
results files (excluding the .chkpnt file) are to be
placed. The directory is created if it doesn’t exist
already. If this keyword is omitted results files are
placed in the directory in which the model was
executed
Default: directory in
which model was
executed
Buscot: results_D
All models
saveint value
Interval in seconds at which results files are saved.
Note each file is saved with a sequential number
Default: 1000
Buscot 10000.0
All models
15
LISFLOOD-FP User Manual
Code release 5.9.6
stamp, e.g. results-0001.wd
massint value
Interval in seconds at which the .mass file is
written to
Default: 100
Buscot: 100.0
All models
sim_time value
Total length of the simulation in seconds (real
value).
Default: 3600
Buscot: 100000.0
All solvers
initial_tstep value
Fixed time step model
Model time step in seconds (real value)
Acceleration and Adaptive time step model
Initial guess for the optimum time step and
maximum possible time step.
Default: 10
Buscot: 1.0
All solvers
bcifile filename
Name of file identifying floodplain boundary
condition types
All solvers
bdyfile filename
Name of file containing information on time varying
channel and floodplain boundary conditions
fpfric value
Manning’s n value for floodplain if spatially
uniform.
If both fpfric and manningfile are
specified, fpfric will not be used
No default
Buscot: buscot.bci
No default value
buscot.bdy available
but commented out
Default: 0.06
Buscot: 0.06
manningfile filename
Name of file containing a grid of floodplain n
values in ARC ascii raster format to allow spatially
variable floodplain friction. This should have the
same dimensions and resolution as the DEMfile. If
both fpfric and manningfile are specified values in
manningfile will be used and fpfric will be
redundant.
No default
Buscot:
buscot.n.ascii
available
but
commented out as
standard so not
used.
2D
model
solvers only
All solvers
2D
model
solvers only
Table 6 Items that turn on or off specific model solvers. If none of these items are entered then
the 1D kinematic solver will be used to river channel flow and the 2D adaptive solver will be used
for floodplain flow
Item name input
Description
Value in the Buscot
weir
test
case
(Diffusive case)
Applicable
model solver
diffusive
As default the code uses the kinematic solver for
the river channel. If this keyword is specified in the
.par file the diffusive solver is used instead.
Option off as default
Used in the Buscot
test case
1D Diffusive
adaptoff
As default the code uses adaptive time-stepping.
This logical keyword suppresses adaptive time
stepping algorithm and a fixed time step is used.
Cannot be used in conjunction with sub-grid
channels as this version of the model uses the
inertial formulation for the 2D model.
Invokes the inertial formulation for the 2D model.
Not needed for sub-grid and cannot be used in
non-adaptive time step model.
Option off as default
Buscot:
keyword
specified to activate
the fixed time-step
version
2D
timestep
Option off as default
Not used in the
buscot test case
Default: off
2D
model
No default value
Not used in Buscot
test case
Subgrid
Option off as default
Not used in Buscot
test case
2D
shallow
water model
acceleration
routing
Routing scheme enabled. Routing only occurs
when depth < depththresh, or when the water
surface slope exceeds routesfthresh. User
should
also
supply
routingspeed,
routesfthresh and depththresh parameter
values (see Table 10). Note: this option can only
be used in conjunction with the Subgrid or 2D
inertial solvers.
SGCwidth filename
Channel widths for the sub-grid channel model.
This file is essential to switch the model to sub-grid
model. It should be noted that sub-grid uses the
2D inertial model for floodplain flow. Note – this
keyword must be accompanied by other subgridspecific par file items given in table below.
Roe
Keyword which turns on the 2D shallow water
model (Roe solver).
*note – don’t use with
“adaptoff”
16
Fixed
inertial
Subgrid and 2D
inertial only
LISFLOOD-FP User Manual
Code release 5.9.6
Table 7 Defining river channel location and properties
Item name input
Description
Value in the Buscot
weir
test
case
(Diffusive case)
Applicable
model solver
riverfile filename
Name of file containing channel geometry and
boundary condition information. Omit if no channel.
Option off as default
Buscot:
buscot_D.river
1D Diffusive and
kinematic
Multiriverfile
filename
Name of file containing index of .river files for
models with multiple 1D river networks in the same
domain.
Option off as default
Not used in the
Buscot test case
1D Diffusive and
kinematic
SGCwidth filename
Channel widths for the sub-grid channel model.
This file is essential to switch the model to sub-grid
model. It should be noted that sub-grid uses the
2D inertial model for floodplain flow.
No default value
Not used in Buscot
test case
Subgrid
SGCbank filename
Channel bank heights file for the sub-grid channel
model. Must be specified but can be the DEM file
No default value
Not used in Buscot
test case
Subgrid
SGCbed filename
Channel bed elevations file for the sub-grid
channel model. If not specified channel
parameters will be used to estimate the depth. If
no channel parameters are provided (see below)
then depth will be estimated assuming a
rectangular cross section channel and geometry
values suitable for an average UK gravel bed river
Default:
values
calculated
as
detailed in box to left
Not used in Buscot
test case
Subgrid
SGCchangroup
filename
Channel parameter regions file for the sub-grid
channel model.
No default value
Not used in Buscot
test case
Subgrid
SGCchanprams
filename
Channel parameters file for sub-grid channel
parameter regions
No default value
Not used in Buscot
test case
Subgrid
SGCn value
Global channel n for the sub-grid channel model.
Default: 0.035
Not used in Buscot
test case
Subgrid
SGCr value
Global parameter for calculating the sub-grid
channel depth.
Default 0.3
Not used in Buscot
test case
Subgrid
SGCp value
Global parameter for calculating the sub-grid
channel depth.
Default: 0.76
Not used in Buscot
test case
Subgrid
SGCchan value
Global sub-grid
(integer).
type
Default:
1
(rectangular)
Not used in Buscot
test case
Subgrid
SGCs value
Global parameter necessary for some sub-grid
channel model shape types.
Default:
2
(parabolic)
Not used in Buscot
test case
Subgrid
channel
model
shape
Table 8 Defining additional water inputs and outputs (rainfall, evaporation and infiltration)
Item
input
name
rainfall filename
infiltration value
Description
Value in the Buscot
weir
test
case
(Diffusive case)
Applicable
model solver
Name of file containing rainfall data. Applies
spatially uniform rainfall field to all cells. . It is
recommended to enable the routing scheme if
DEM contains any steep slopes (see routing
keyword).
Spatially uniform infiltration rate for the floodplain
-1
in ms .
Option off as default
Not used in the
Buscot test case
All 2D models
Default: 0
Buscot: 0.0000001
All 2D models
except Roe
17
LISFLOOD-FP User Manual
evaporation filename
Code release 5.9.6
Name of file containing evaporation data.
but commented out
Option off as default
Not used in the
Buscot test case
All 2D models
except Roe
Table 9 Options relating specifically to model starting conditions
Description
Value in the Buscot
weir test case
(Diffusive case)
Applicable
model solver
Options to change the simulation start time. Units
are seconds
Default: 0
Not used in the
Buscot test case
All models
checkpoint value
Logical keyword which turns on checkpointing.
Followed by interval in hours of computation time
at which checkpointing occurs. If no value is set a
default value of 1 hour is used. When the model
starts it automatically looks for and reads in the
default file named “resroot”.chkpnt in the
directory from which the model was executed,
unless the loadcheck keyword with alternative
filename is used. The user needs to delete the
.chkpnt or turn off this option to commence the
simulation again from the beginning.
Option off as default.
If
keyword
is
specified
then
default value is 1
(hr).
Not used in the
Buscot test case
(commented out)
All
models
except Roe (in
theory)
loadcheck filename
Name of an alternative file used to start the
checkpointing. By default, the program uses a
single file which is overwritten at the checkpointing
interval. This alternative start file allows you to
start from a file that does not get overwritten by the
checkpoint function
Option off as default.
Not used in the
Buscot test case
All
models
except Roe (in
theory)
ch_start_h value
By default, the channel solver will start with a
water depth of 2m for the whole channel. The user
can override this by using this option and a value.
This can speed up the spinup time of the model.
Default: 2
Not specified in the
Buscot test case
1D Diffusive and
kinematic
startq
In kinematic mode, the model will calculate a water
level for each section given the inflow at the top of
the reach. In diffusive mode, the model will iterate
to the initial steady state solution given a
downstream boundary condition and an upstream
inflow. Will dramatically decrease spin up time for
complex channels. See “ch_dyanmic” below for
more details
Option is off as
default
Not used in the
Buscot test case
1D Diffusive and
kinematic
ch_dynamic
Startq will automatically use the diffusive steady
state solution in diffusive mode. Use this keyword
to activate full dynamic steady state initial
condition. Mainly incorporated for forward
compatibility and very complex channel systems.
Can only be used in conjunction with “startq”
Option is off as
default
Not used in the
Buscot test case
1D Diffusive
binarystartfile
filename
This is the same as the keyword startfile (above)
but the input data are in binary format.
As
default this option is off and this keyword must be
specified to activate it
Option is off as
default.
Not used in the
Buscot test case
All 2D models
and subgrid
Similar to startfile but initialises the model with
water surface elevation rather than depth.
As
default this option is off and this keyword must be
specified to activate it
Option is off as
default.
Not used in the
Buscot test case
All 2D models
and subgrid
Name of previous results file in ARC ascii raster
format used to provide initial conditions for a model
simulation. This should be a water depth file
Option is off as
default Not used in
Buscot test case
(commented out)
All 2D models
except Roe
Item name input
tstart value
startelev filename
startfile filename
Table 10 Additional, less commonly used settings and parameters
Item name input
Description
Value in the Buscot
weir
test
case
18
Applicable
model solver
LISFLOOD-FP User Manual
Code release 5.9.6
(Diffusive case)
ts_multiple value
Decouples the channel and floodplain time step
and increases the channel timestep. Enter a value
after the keyword to invoke more than x1. Tests
show up to x10 gives almost identical results to x1.
If used, check sensitivity of results.
htol value
Optional parameter to override default 1m bank
smoothing.
chainageoff
As default the code now makes river channel
chainage independent of cell size and uses
straight line distance between entered sections.
Use this keyword to revert to the old calculation
which used cell dx dimensions.
depththresh value
Option off as default.
If
keyword
is
specified
default
value is 1.
Not used in the
Buscot test case
Option is off as
default.
Not used in the
Buscot test case
Option off as default,
Used in the Buscot
test case
1D Diffusive and
kinematic
Option to change the depth at which a cell is
considered wet (in metres).
Also controls
threshold beneath which the rainfall routing
scheme operates (if enabled).
Name of file containing information on location and
nature of any weir or bridge linkages between cells
to be included in the model.
Default: 0.001
Not used in the
Buscot test case
All 2D models
and subgrid
No default value
buscot.weir
cfl value
Option to change the stability coefficient used to
determine the model time step.
Default: 0.7
Not used in the
Buscot test case
2D All models
for weirs and
subgrid
channels
only
for bridges
2D inertial and
shallow
water
models and subgrid
drycheckon
Turns on drycheck (see Bates and de Roo 2000).
Default: drycheck is
off
Not used in the
Buscot test case
2D
Adaptive,
and
fixed
timestep
and
inertial models
drycheckoff
Turns off drycheck (see Bates and de Roo 2000).
2D
Adaptive,
and
fixed
timestep
and
inertial models
routingspeed value
Sets speed (ms ) at which water is routed across
domain if routing scheme is enabled.
routesfthresh value
Water surface slope above which routing occurs if
routing scheme is enabled. Used to enable model
stability and conserve mass in areas of steep
terrain.
Default: drycheck is
off
Not used in the
Buscot test case
Option off as default,
if routing active then
default value is 0.1
Not used in the
Buscot test case
Default: 0.1
Not used in the
buscot test case
dhlin value
Option to change linearisation threshold for
adaptive version. Increasing the value reduces run
time and accuracy. As default the dhlin value is
calculated for each simulation as dx times 0.0002
from Cunge et al., 1980 and Hunter et al., 2005
Option to include cell porosity details within the
model, i.e. the portion of each cell which is likely to
be inundated.
Please email for Tim Fewtrell’s
Porosity manual for full details. Note - while the
code for this works fine, the methodology is still at
the development stage.
Option to change to a 1D friction treatment when
using the inertial model
Default: see text to
left
Not used in the
Buscot test case
2D
Adaptive
timestep
Option off as default
Not used in the
Buscot test case
2D
Adaptive
time-step
Option off as default
(uses 2D friction
treatment)
Not used in Buscot
test case
2D inertia model
Adds numerical diffusion to the inertial model if
below 1.
Default: 1
Buscot: not specified
2D
model
Option to change the threshold for the momentum
equation used by the Roe solver.
Default: 0.001
Not used in Buscot
2D
Shallow
water model
weirfile filename
porfile filename
1Dfriction
theta value
momentumthresh
value
-1
19
1D Diffusive and
kinematic
1D Diffusive and
kinematic
Subgrid and 2D
inertial only
Subgrid and 2D
inertial only
inertial
LISFLOOD-FP User Manual
qlimfact value
gravity value
latlong
Code release 5.9.6
Keyword which allows the user to vary the flow
limit in the fixed time-step 2D solver by a specified
factor. The calculated flow limit will be multiplied
the input value
Keyword used to change the gravity value used for
-2
calculations, in ms
In development. Option to change all coordinates
and cell dimensions to decimal degrees. This
means lisflood will expect and values relating to
location or cell size to be in decimal degrees (ascii
file headers, bci, stage, gauge and weir files etc)
3 -1
and any flow rates to be in m s (bdy and bci file)
test case
Default: 1
Not used in the
buscot test case
Default: 9.81...
Default: off
Not used in buscot
test case
2D
timestep
Fixed
2D inertia model
and subgrid.
Subgrid
Table 11 Options related to additional output files or output settings
Item name input
Description
Value in the Buscot
weir
test
case
(Diffusive case)
Applicable
model solver
overpass value
Time in seconds at which an observed flood image
is available for model validation. When specified
the model writes a set of results files (water depth
*.op and water surface elevation
*.opelev) at this point in the simulation to allow
easy model validation
Option off as default
Buscot: 100000
All models
overpassfile
filename
Name of file containing times of multiple satellite
overpasses. See section 3.2.15. water depth and
surface elevation files are produced for each
overpass time (*-xxxx-T.op and *-xxxxT.opelev)
No default value
Buscot.opts
available
but
commented out
All models
stagefile filename
Name of file containing x, y locations of points at
which stage values are to be written to a text file
(*.stage) at each massint
No default value.
Not used in buscot
test
case
(commented out)
All models
depthoff
Logical keyword to suppress production of depth
files (*.wd) at each saveint If simulation uses
subgrid, *.wdfp files are also suppressed.
Option off as default
Not used in buscot
test
case
(commented out)
All models
elevoff
Logical keyword to suppress production of water
surface elevation files (*.elev) at each
saveint
and
overpass
time
if
specified
(*.opelev
and
*-xxxxT.opelev).
Option off as default
Used in buscot test
case
All models
resettimeinit value
Resets the time of initial inundation counter to zero
at a specified time by the user. The keyword
should be followed by the time in seconds at which
the reset should take place.
Default: 0
Not used in the
Buscot test case
All models
ascheader filename
Name of file containing alternative header
information for output of ascii raster grids. Useful
for switching to lat/long format.
Option off as default
Not used in the
Buscot test case
All models
debug
Outputs a number of useful files; the final dem
after burning in the channel and bank mods
(*.dem, in subgrid mode this is
simply the input dem), the channel mask
(*.chmask) and the channel segment mask
(*.segmask).
If subgrid is used then files
containing details of the subgrid bed elevations,
the bankfull depth and the channel width are
produced
instead
(*_SGC_bedZ.asc,
*_SGC_bfdepth.asc, *_SGC_width.asc).
Option off as default
Not used in the
Buscot test case
All models
mint_hk
Keyword to allow calculation of maxH (maximum
water depth), maxHtm (time of maximum water
depth), totalHtm (total inundation time) and
initHtm (initial inundation time) at the mass
interval rather than every time-step. Useful for
parallel
solutions
and
should
decrease
Option off as default
Not used in the
Buscot test case
All models
20
LISFLOOD-FP User Manual
Code release 5.9.6
computation time. This related to ascii raster grids
*.max, *.mxe, *.inittm, *.maxtm and
*.totaltm
comp_out
Keyword to initiate model time/computation time
ratio output to standard out buffer. Details in
section 6 below.
Option off as default
Not used in the
Buscot test case
All models
profiles
Keyword which forces the model to produce
channel water surface profile files (*.profile) at
each saveint. If any overpass times are also
specified then water surface profile files are also
produced for these times.
Option off as default
Not used in the
Buscot test case
1D
Kinematic
and Diffusive
qoutput
Keyword which forces the model to write out ascii
raster grid files of the floodplain flux values in the x
and y Cartesian directions (*.Qx and *.Qy). In
subgrid mode then channel grids of channel flux
values and channel flow width are also produced
(*.Qcx, *.Qcy and *.Fwidth). Grids are
output at each saveint.
Option off as default
Not used in the
Buscot test case
(commented out)
All 2D models
and subgrid
voutput
Keyword which forces the model to write out ascii
raster grid files (*.Vx and *.Vy) of the velocity
values in the x and y Cartesian directions. Grids
are output at each saveint. As default this
option is off and this keyword must be specified to
activate it
Option off as default
Not used in the
Buscot test case
All 2D models
and subgrid
Tells the model to read a file containing x,y
locations of virtual gauging stations where
discharge will be measured and written to a text
file (*.discharge).
Option off as default
Not used in the
Buscot test case
All 2D models
and subgrid
Switches grid output from ascii raster to double
precision binary data and adds suffix “b” to all
filenames e.g. *.wd->*.wdb. Does not include
grids associated with the debug keyword.
Forces the model to write out ascii raster grid files
related to the water velocity at each saveint (*.Vx,
and *.Vy), and related to the maximum velocity
values, water depths and hazard for each
simulation (*.maxVx,
*.maxVy, *.maxVc,
*.maxVcd and *.maxHaz)
Keyword which forces the model to write out ascii
raster grids of the per cell flow limiter values
calculated by the adaptive time stepping routine.
Grids are output at each saveint and separate
values are calculated for the x and y Cartesian
directions (*.QLx and *.QLy).
Option off as default
Not used in the
Buscot test case
All 2D models
and subgrid
Option off as default
Not used in the
Buscot test case
All 2D models
and subgrid
Option off as default
Not used in the
Buscot test case
2D
timestep
gaugefile filename
binary_out
hazard
qloutput
fixed
An example .par file for the Buscot application is given below (this is the buscot_D.par file
provided with the download):
DEMfile
resroot
dirroot
sim_time
initial_tstep
massint
saveint
#checkpoint
overpass
fpfric
#infiltration
#overpassfile
#manningfile
riverfile
bcifile
#bdyfile
buscot.dem.ascii
res_D
results_D
100000.0
1.0
100.0
10000.0
0.00001
100000.0
0.06
0.000001
buscot.opts
buscot.n.ascii
buscot_D.river
buscot.bci
buscot.bdy
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LISFLOOD-FP User Manual
weirfile
#startfile
#stagefile
elevoff
#depthoff
diffusive
adaptoff
#qoutput
chainageoff
Code release 5.9.6
buscot.weir
res.old
buscot.stage
As this application involves a steady state, fixed timestep simulation and a single satellite
overpass, the time varying boundary condition file name (bdyfile) and the overpass file name
(overpassfile) have been commented out and the keyword adaptoff specified. The simulation
also uses a spatially uniform floodplain friction, includes weirs, and begins from the default initial
conditions with no checkpointing. Stage outputs at locations within the domain, water elevation
grids and flux grids are not requested, but water depth grids are. The results files all have the
suffix .res_D and are placed in the directory ./results_D.
3.2.2 Channel information file (.river)
This file gives information on the location and nature of the channels along the reach. For a
model domain containing no channel this file is omitted. The channels are discretised as a single
vector along the centreline and the model then interpolates this vector onto the raster grid
specified by the user. The vector should run beyond the edge of the model domain. However
there should be no more than one point off the model domain at the upstream and downstream
ends of a river and no more than one vector point in any DEM cell (so an x and y point in the .river
file should never be in the same DEM cell as another). Each channel is described in terms of its
width, Manning’s n friction coefficient and bed elevation (so hence channel depth when combined
with the floodplain elevation described in the DEM) and the linkages between different tributary
channels are prescribed using a series of keywords. The user then has two options for
prescribing this information.
Option 1: Uniform channel
Characteristics for each channel are provided for the first and last points of the channel vector,
and the code automatically fills in intermediate points by linear interpolation. By specifying the
channel bed elevation at the first and last points on the channel vector the user is able to specify
the (uniform) bed slope for that channel reach.
Option 2: Spatially variable channel
Additional values can be specified at any point along the reach, but all 3 values for width,
Manning’s n and bed elevation must be supplied. One should note that for the kinematic
approximation to in-channel flow, the down reach slope should be negative (or positive downhill)
(i.e. the channel bed should not increase in elevation in the downstream direction). LISFLOOD-FP
will allow uphill slopes for the kinematic solver, but just pretend they are downhill and give a
warning. The diffusive solver can handle uphill slopes so no warnings are issued.
The file is formatted as follows
Line 1:
Line 2:
Line 3:
Line 4:
Line 5:
etc……
Line i:
Keyword Tribs followed by number of channel
channel reach)
Number of data points in the channel vector (i)
X1
Y1
Width1
n1
X2
Y2
Width2
n2
X3
Y3
Width3
n3
…
…
…
…
Xi
Yi
Widthi
ni
segments (if this line is omitted the model assumes a single
Bed
Bed
Bed
…
Bed
elevation1
elevation2
elevation3
BC
Lateral inflow2
Value
elevationi
Hence, values for channel width, Manning’s n, and bed elevation between line 2 and line i-1 are
optional. The first point on the vector must also contain a boundary condition (BC) for the inflow
discharge and its value. Here again the user has two options:
22
LISFLOOD-FP User Manual
Code release 5.9.6
Option 1: Constant inflow.
To use this option to simulate steady state flow BC is given the keyword QFIX and the associated
value is the inflow discharge at the upstream end of the model in m3s-1.
Option 2: Time-varying inflow.
To use this option to simulate a dynamic flood wave BC is given the keyword QVAR and the
associated value is a boundary identifier chosen by the user, e.g. upstream1. Information about
the time varying boundary condition data is then held in the time varying boundary condition file
(.bdy).
At any point along the reach a lateral inflow may be specified as a source term to represent minor
tributary inflows or other catchment hydrological processes which do not require a channel to be
represented. Width, Manning’s n etc do not need to be given at these points, but can be if
necessary.
An example .river file for the Buscot application is given below:
Tribs 1
133
22950.000
23107.670
23140.552
23183.698
etc….
-1930.000
-1929.020
-1924.844
-1931.253
….
20.000
0.03
68.740479
QFIX 73.0
20.000
0.03
68.5
QVAR latinflow1
26739.636
26759.629
26781.873
-1161.781
-1130.894
-1104.059
25.000
0.04
68.230
20.000
0.03
67.139
The file thus denotes a fixed inflow of 73m 3s-1, with channel width starting at 20m, increasing to
25m and back down to 20m, and a time varying lateral inflow at (23183.698, -1931.253) with
values found in the latinflow1 part of the .bdy file (see below).
The keyword identifier format for lateral inflows also provides the means of describing how
tributary channels connect. For a .river file with multiple tributary channels the keyword Tribs
on line one of the river file is followed by an integer number which specifies the number of
channel segments. If this line is omitted, or if this keyword equals 1, then the model assumes that
there is a single channel reach. If multiple segments are present then the first channel is always
the main stem. At each point along the main stem where a tributary river enters the user specifies
the channel width, Manning’s n and bed elevation and follows this by the keyword Trib and an
integer number. This number identifies the segment number in the .river file which discharges
into the main stem at this point. Segments are numbered sequentially in the order they appear in
the .river file starting at 0 (which should be the main stem). Each channel segment is
described in the .river file in exactly the same way as a single channel would be, with the
exception that the x, y co-ordinates, width, Manning’s n and bed elevation for the last point on
each segment is followed by the keyword QOUT followed by the number of the channel segment
into which this tributary discharges. The format is thus:
Line 1:
Line 2:
Line 3:
Line 4:
etc……
Line i:
Number
X1
X2
X3
…
Xi
of data points in the channel vector (i)
Y1
Width1
n1
Y2
Width2
n2
Y3
Width3
n3
…
…
…
Yi
Widthi
ni
Bed
Bed
Bed
…
Bed
elevation1
elevation2
elevation3
BC
Lateral inflow2
elevationi
QOUT
Value
Segment number
Repeating this process allows a dendritic drainage pattern with infinite stream order to be
described. As an example, the following is a .river file for the Buscot reach assuming a single
tributary joining the main stem. In addition this tributary is itself joined by a single tributary. Time
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varying discharge into the head of each channel segment is described by the keywords
upstream1, upstream2 and upstream3.
Tribs 3
133
22950.000
23107.670
23140.552
25617.870
-1930.000
-1929.020
-1924.844
-1428.595
etc….
….
26706.838
26739.636
26759.629
26781.873
3
24350.0
24900.0
25617.870
2
22950.0
24900.0
20.000
0.03
68.740479
20.000
0.03
-1179.890
-1161.781
-1130.894
-1104.059
20.000
0.03
67.139
0.0
-600.0
-1428.595
5.0
5.0
5.0
0.03
0.03
0.03
-600.0
-600.0
5.0
5.0
0.03
0.03
68.0
QVAR upstream1
TRIB
1
69.0
68.5
68.0
QVAR
TRIB
QOUT
upstream2
2
0
69.0
68.5
QVAR
QOUT
upstream3
1
Downstream Boundary Conditions for the Diffusive Channel Solver
Unlike the kinematic solver, the diffusive channel solver requires a downstream boundary
condition. For tributaries this is handled automatically by LISFLOOD-FP, which uses the water
level from the downstream receiving channel. However, for the main channel a boundary
condition will have to be provided by the user – and you will be warned if it is not present.
Currently there are two fully tested options for this.
Option 1: Normal depth calculation
To use this option, use the keyword FREE to force the model to calculate the normal depth for the
downstream water level. There are two options available of which the latter is considerably more
stable. Option a is to allow the model to calculate the slope used for the normal depth calculation
which uses the slope between the last two river sections e.g.
22950.0
24900.0
-600.0
-600.0
5.0
5.0
0.03
0.03
69.0
68.5
FREE
Option b is to specify a user determined slope which is normally taken as the overall valley slope
e.g.
22950.0
24900.0
-600.0
-600.0
5.0
5.0
0.03
0.03
69.0
68.5
FREE
0.0006
Option 2: Constant water level.
To use this option to simulate a steady state water level BC, use the keyword HFIX and the
associated water ELEVATION value at the downstream end of the model in m. e.g.
22950.0
24900.0
-600.0
-600.0
5.0
5.0
0.03
0.03
69.0
68.5
HFIX
38.345
Option 3: Time-varying water level.
To use this option to simulate a dynamic flood wave BC, use the keyword HVAR and the
associated value is a boundary identifier chosen by the user, e.g. downstream1. Information
about the time varying boundary condition data is then held in the time varying boundary condition
file (.bdy).
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3.2.3 Multiple unconnected channels (.rivers)
This file is used as an index of .river files and is required when there are two or more 1D channel
networks within a model domain. It is therefore needed if you wish to model multiple catchments
that supply different main stem rivers within the same domain. It is NOT needed for a single
network of sub-catchments where all tributaries supply the same main stem channel; this scenario
is handled within a single .river file.
The file is read when the keyword multiriverfile appears in the .par file. The first line of
the file specifies the number of .river files in the model. The following lines supply the file
names of the .river files. For example:
Line 1: 3
Line 2: Thames.river
Line 3: Severn.river
Line 4: Avon.river
Each of the individual .river files behave as normal and should be written as instructed in
section 3.2.2. Be careful not to repeat boundary condition names in different .river files unless
you want to use the same condition across multiple rivers.
3.2.4 Boundary condition type file (.bci)
This file specifies boundary conditions not associated with the channel. There can be any number
of boundaries on the edge of the domain or at points within the domain itself. There must not be
more than one point source per cell.
Column 1: Boundary identifier taking a value of N, E, S, W or P and referring to the north, east, south or west boundaries
or P referring to a point source
Column 2: start of boundary segment (easting or northing in map co-ordinates or decimal degrees in the WGS 84 system
if using the latlong option) for edge boundaries or easting in map co-ordinates or decimal degrees for a point source
location
Column 3: End of boundary segment (easting or northing in map co-ordinates or decimal degrees in the WGS 84 system if
using the latlong option) for edge boundaries or northing in map co-ordinates or decimal degrees for a point source
location
Column 4: Boundary condition type
Column 5: Boundary condition value. This varies according to boundary condition type as indicated in Table 12.
Possible boundary condition types and their associated values are given in Table 12.
Table 12: Types of boundary condition available in the .bci file.
Boundary
condition type
Description
Value supplied in column 5 of the .bci file
CLOSED
Zero-flux (default option)
None
FREE
Uniform flow
Free surface or valley slope (optional)
HFIX
Fixed free surface elevation
Free surface elevation in metres
HVAR
Time varying free surface elevation,
Boundary identifier (e.g. downstream1)
corresponding to data in the user supplied .bdy
file.
QFIX
Fixed flow into domain
Mass flux per unit width (m s ).
For a
boundary segment this is multiplied within the
code by the length of the boundary segment to
3 -1
give the mass flux in m s . For a point source
the mass flux per unit width is multiplied by the
3 -1
cell width to the mass flux in m s . Note if the
keyword latlong is specified then this value
3 -1
must be in terms of volume flux instead (m s )
QVAR
Time varying flow into domain
Boundary
identifier
(e.g.
upstream1)
corresponding to data in the user supplied .bdy
file
2 -1
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An example .bci file for the Buscot application is given below:
E
-1200
-1800
HFIX
69.000
This specifies a fixed free surface elevation boundary on the east side of the domain between
northing co-ordinates -1200 and -1800 (i.e. on the y axis).
3.2.5 Time varying boundary conditions file (.bdy)
This file is used to specify time varying boundary conditions (keywords QVAR or HVAR in the
.river or .bci files) associated with a channel segment, boundary segment or point source.
For each time varying boundary condition the format for the file is as follows:
Line 1: Comment line, ignored by LISFLOOD-FP.
Line 2: Boundary identifier (this should be consistent with notation supplied in the .river or .bci file).
Line 3: Number of time points at which boundary information is given followed by a keyword for the time units used (either
‘days’, ‘hours’ or ‘seconds’).
Line 4: Value1
Time1
Line 5: Value2
Time2
etc…. …
…
Line i: Valuei
Timei
Where Valuei is the value of the relevant quantity for the given boundary type. For all HVAR
boundaries Valuei is a water surface elevation in metres. However, the units of Valuei for QVAR
boundaries depend on whether the given boundary identifier is specified in the .river or .bci
files. This seems complex, but is a consequence of having a 1D channel model coupled to a 2D
floodplain model and actually makes setting up the code a lot easier. For a QVAR boundary
specified in the .river file Valuei is given as mass flux with units of m3s-1. By contrast, for a
QVAR boundary specified in the .bci file Valuei is given as mass flux per unit width with units of
m2s-1. In this latter case the flux per unit width is multiplied within the code either by the length of
the boundary segment (for a boundary flux) or the cell size (for a point source) to give the mass
flux in m 3s-1.
Note if the keyword latlong is specified then QVAR values must be given in
terms of volume flux instead (m 3s-1) to account for varying cell dimensions in terms of meters.
An example .bdy file for the Buscot application is given below
QTBDY
Obtained from results file C:\HALCROW\KISMOD\KISL_100.ZZN
downstream1
3
seconds
70.
0
71.000
25000
70.000
50000
This specifies a water surface elevation varying in time between 70 and 71m for the boundary
segment identified by the keyword downstream1. The location of this segment is specified in the
.bci file. Currently the only supported units are “seconds” and “hours”. If an identifier specified
in the .river or .bci file is not found in the .bdy file, or one found in the .bdy file has no
reference in the .river or .bci file, a warning is output (verbose mode only - see below) and the
boundary defaults to zero flux.
3.2.6 Digital Elevation Model file (.dem.ascii)
This file specifies the Digital Elevation Model used by the model. It consists of a 2D raster array
of ground elevations in ARC ascii raster format. The file may be manipulated using either the
ARC-View or ARCGIS Geographical Information System platforms or manually edited using a text
editor. For full details on the ARC ascii raster format the user is referred to the ARC
documentation. A brief summary of the format is provided below.
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The file consists of a 6 line header followed by the numerical values of each data point on the grid
as a 2D array of i rows and j columns. Each line of the header consists of a self-explanatory
keyword followed by a numeric value. As an example, the header for the Buscot application is
given below (comments in brackets are not part of the file format):
ncols
nrows
xllcorner
76
48
22950
yllcorner
-2400
cellsize
NODATA_value
50.0
-9999
(Number of columns)
(Number of rows)
(X cartesian co-ordinate of the
corner of the grid in metres*)
(Y cartesian co-ordinate of the
corner of the grid in metres*)
(Cell size in metres*)
(Null value)
lower
left
lower
left
*Note if the keyword latlong is specified in the par file then xllcorner, yllcorner and
cellsize must be given in terms of decimal degrees.
3.2.7 Porosity file
This allows details of the proportion of each cell in the grid which can become inundated (thus
affecting the water capacity of the cell) to be simulated. There are currently 4 methods
implemented, ranging from fixed porosity values to those which vary with inundation height, with
additional options for how individual cell boundaries are treated, The porosity file is set out like a
model .par file and instructs the model to read in a number of other files and set values for
related parameters. It also produces some additional related output files. Please email to request
Tim Fewtrell’s Porosity Manual for full details. Note - while the code for this works fine, the
methodology is still at the development stage and may give unexpected results.
3.2.8 Floodplain friction coefficient file (.n.ascii)
This file can be used by the user to specify a spatially variable friction coefficient across the
floodplain by assigning values of Manning’s n to each cell on the raster grid. Again, the file format
is an ARC-Info ascii raster as described in section 3.2.6 above.
3.2.9 Sub-grid model river width file (.width.asc)
This file can be used to specify the locations of sub-grid channel in the raster grid. Like the DEM
the file is in ARC-Info ascii raster format. Each cell can contain one value for the river width. If no
channels exist in a cell the value of that cell should be zero or NoData.
3.2.10 Sub-grid model bed elevations file (.bed.asc) (optional)
This file can be used to specify the bed elevation of sub-grid channels in the raster grid. Like the
DEM the file is in ARC-Info ascii raster format. Each cell can contain one value for the river bed
elevation. If there is no channel width in a cell, as specified in the width file, the bed elevation
value will have no effect. If the bed elevation is unknown in a cell the value should be set to
NoData. When the bed elevation is set to NoData but the channel has a width, the width and
bank height and either a channel parameter file or default channel parameter values will be used
to calculate the channel depth and bed elevation. Default values assume a rectangular cross
section channel and are based on an average UK gravel bed river.
3.2.11 Sub-grid model bank elevation file (.bank.asc)
This file can be used to specify the elevation of the river banks from which the bed elevation is
calculated using the river channel parameters in the sub-grid parameter file (.pram) (section
4.2.11). Like the DEM the file is in ARC-Info ascii raster format. The bank elevations do not
control when the river banks overtop, this is determined by the elevation in the DEM, however,
they do have an effect on the channel bed elevation. If the DEM elevation and the bank elevation
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are the same the DEM can be used for this file. Elevations in cells without channel widths are
ignored by the model. In the case of NoData the DEM elevation will be used.
3.2.12 Sub-grid model channel region file (.region.asc) (optional)
This file can be used to split up the sub-grid channels into regions of homogeneous
parameterisations, without this file the model will apply the same sub-grid channel parameters to
the whole domain. Like the DEM the file is in ARC-Info ascii raster format, however the values in
the cells should be integers. Regions should start from 0 up the number of regions that are
required in the model domain; there is no limit on the number of separate regions however each
region will require parameters in the .pram file. Where there is no channel in a cell the region will
have any effect on the model.
3.2.13 Sub-grid model channel parameter file (.pram) (optional)
This file is used to specify the channel parameters of each region of the model domain as defined
in the .region.asc file. For each region the format for the file is as follows:
Line 1: Number of regions in the model domain (integer). This must match the number of regions in the .region.asc file
Line 2: Region1
Type1
p1
r1
s1
nch1
m1
Line 5: Region 2
Type2
p2
r2
s2
nch2
m2
etc…. …
…
Line i: Region i
Typei
pi
ri
si
nchi
mi
Where Region1 is the integer region number that matches a region in the .region.asc file. This
should start at 0 and count to the number of regions-1. Type is the type of channel, this is an
integer value and will be 1 for a rectangular channel, Table 13 below gives more information on
alternative channel types. r and p control the depth of the channel given the widths, where cell
channel depth = r*width^p. Channel bed elevation is then the banks elevation minus channel
depth. S is an additional parameter for some types of channel model. In the case of the
rectangular sub-grid channel S has no effect but it is needed for some of the other channel types
(see Table 13). nch is the channel Manning’s coefficient. Finally, m is an optional meander
coefficient, each cell is assumed to contain a channel of length dx*m, where m is 1 by default and
thus has no effect. A value of m above 1 will lengthen the channel while a value below 1 will
shorten it. Note that values of m below 1 may also reduce the model time step.
Table 13: Simple shapes of sub-grid channels
Channel Type
Channel shape
Impact of parameter s
1
Rectangular channel
None
2
Power
Determines the shape of the channel
An example .pram file is given below, the first channel is rectangular and the second is a power
shape. Both channels have the same width depth relationship and Manning’s coefficient. The third
channel is the same as the first but has a higher friction coefficient and will be 10% deeper for the
same channel width.
3
0
1
2
1
2
1
0.30
0.30
0.33
0.78
0.78
0.78
-9999 0.035
3.2
0.035
-9999 0.045
3.2.14 Weir & bridge cell linkage specification file (.weir)
The location and properties of weir and bridge type objects in the domain are both read in using
the .weir input file. The format of the direction information in the input file is used to specify
whether a feature should be treated by lisflood as a weir-type or bridge-type object.
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3.2.14.1
Code release 5.9.6
Weirs, embankments and structures
If weirs are to be included in the model then appendix 6.1 which gives further details on these
calculations (including their limitations) must be read. Information about these linkages is given in
the .weir file. The file format is as follows:
Line 1; total number of weir and bridge-type linkages between cells (i).
Line 2;
X1
Y1
Direction1
C1
Line 3:
X2
Y2
Direction2
C2
etc…
…
…
…
…
Line i:
Xi
Yi
Directioni
Ci
Crest height1
Crest height2
…
Crest heighti
Modular limit1
Modular limit2
…
Modular limiti
Width1
Width2
…
Widthi
where X and Y are the grid co-ordinates in Eastings and Northings of a cell with a weir linkage*.
X and Y can be located anywhere within the cell being identified. Direction identifies the cell face
with the linkage N, E, S or W (Obviously 10 42 W is the same as 10 41 E). If flow in only one
direction is required (e.g. for a culvert), the direction may be fixed by using the tags NF, EF, SF,
or WF. C is the weir flow coefficient, typically ranging from 0.5-1.7 and taking a value if 1.4 for a
standard broad crested weir. Crest height is the height of the weir in m.a.s.l or the co-ordinate
system being used in the model. Modular limit is the modular limit of the weir, typically 0.9. Width
is an optional width for the weir which defaults to the grid size if not supplied.
An example .weir file for the Buscot application is given below. Note that the weir width is not
specified so a grid size (50m) is used as a default.
14
22950
23000
23050
23100
23150
23200
23250
23300
Etc
-1700
-1700
-1700
-1700
-1700
-1700
-1700
-1700
N
N
N
N
N
N
N
N
1.7
1.7
1.7
1.7
1.7
1.7
1.7
1.7
72
72
72
72
72
72
72
72
0.9
0.9
0.9
0.9
0.9
0.9
0.9
0.9
*Note if the keyword latlong is specified in the par file then X and Y locations must be given in
terms of decimal degrees (although crest heights and widths remain in meters).
3.2.14.2
Bridges (currently subgrid channel version only)
If bridges are to be included in the model then appendix 6.2 which gives further details on these
calculations (including their limitations) must be read. Currently bridges have only been
implemented in the subgrid channel version. Like weirs, information about bridge linkages is also
given in the .weir file. The file line format for bridges is as follows:
X1
Y1
Direction1
Cd1
Soffit elevation1
Transition zone1
Width1
where X and Y are the grid co-ordinates in Eastings and Northings of a cell with a weir linkage*.
X and Y can be located anywhere within the cell being identified. Direction identifies the cell face
with the linkage N, E, S or W (Obviously 10 42 W is the same as 10 41 E). When stating the
direction you must put n, s, e, w (north, south ...) followed by a b for bridge. Cd is the
coefficient of discharge for a fully submerged pressure flow, typically 0.8. Soffit elevation is the
underside of the bridge deck elevation. Transition zone is the upper end of the zone for which
lisflood-fp will take a weighted mean of the open channel flow and pressure flow (the lower end of
the zone has a value of 1.0 and represents the point where the water elevation is equal to the
soffit elevation). Typically for a bridge this should be a value of 1.5, see appendix 6.2for further
details. Width is the width of the bridge opening.
*Note if the keyword latlong is specified in the par file then xllcorner, yllcorner and
cellsize must be given in terms of decimal degrees (although soffit elevation and widths
remain in meters).
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3.2.15 Multiple overpass file (.opts)
This file is used to specify the times in seconds of multiple satellite overpasses during a single
simulation. This option is activated by including the optional keyword overpassfile followed
by a filename in the .par file. The model then outputs a set of results files at each time specified,
with the file naming including a simple counter (beginning at 0000) to signify each overpass
requested. It is important to remember that the model time that the overpass counter signifies is
not the same as that of the regular file output interval counter. The file format is as follows:
Line 1; Number of satellite overpasses
st
Line 2;
Time of 1 overpass in seconds of simulation time
nd
Line 3:
Time of 2 overpass in seconds of simulation time
etc…
…
…
…
…
th
Line i:
Time of n overpass in seconds of simulation time
…
…
…
An example .opts file is given below:
4
900.0
1800.0
2700.0
3600.0
3.2.16 Stage output data file (.stage)
This file is used to specify the x,y locations of points where the user wishes the model to output a
time series of water depths. This option is activated by including the keyword stagefile in the
.par file and following this with the name of the .stage file to be read. For each location
specified in the file the water depth value is written out at each massint interval. The format of
the file is as follows:
Line 1;
Line 2;
Line 3:
etc…
Line i:
Number of stage points at which water depth output time series are required
st
x and y locations of 1 point
nd
x and y locations of 2 point
…
…
…
…
…
th
x and y locations of n point
…
…
An example .stage file is given below:
3
388869.59
386307.41
383681.45
233696.3
239076.1
245652.34
3.2.17 Evaporation data file (.evap)
This file is used to specify a time-varying evaporation rate and is read when the keyword
evaporation appears in the .par file. This sink term is then applied to every model grid cell at
each time step to give a spatially uniform evaporation loss over the domain. The file format is
similar to the .bdy file:
Line 1: Comment line, ignored by LISFLOOD-FP.
Line 2: Number of time points at which boundary information is given followed by a keyword for the time units used (either
‘days’, ‘hours’ or ‘seconds’).
Line 3: Value1
Time1
Line 4: Value2
Time2
etc…. …
…
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Line i: Valuei
Code release 5.9.6
Timei
Where Valuei is evaporation rate in mm day-1 and Timei is the time at which this value occurs in
the units specified on line 2. The model then linearly interpolates these values to give the
evaporation rate at each time step.
3.2.18 Alternative ascii header file (.head)
This file is used to an alternative 6 line header for all ascii raster file output by the model and is
read when the keyword ascheader appears in the .par file. This is particularly useful for
switching between different coordinate systems (e.g. UTM to lat/long). The format is identical to
that given in Section 3.2.6 and each line of the header consists of a self-explanatory keyword
followed by a numeric value.
3.2.19 Virtual gauge output data file (.gauge)
This file is used to specify the x,y locations and lengths of cross-sections where the user wishes
the model to output a time series of discharge crossing the section. This option is activated by
including the keyword gaugefile in the .par file and following this with the name of the
.gauge file to be read. For each location specified in the file the direction identifies the cell face
from which discharge will be measured and the direction of positive flow (e.g. N, E, S or W). The
width is then the length of the cross section in an easterly direction for measuring flows to the
north and south, and a southerly direction for flows to the east or west (note that the distance will
be rounded up to nearest cell width). The discharge value is written out at each massint
interval. The format of the file is as follows:
Line 1; number of virtual gauge sections.
Line 2;
X1
Y1
Direction1
Line 3:
X2
Y2
Direction2
etc…
…
…
…
Line i:
Xi
Yi
Directioni
Width1
Width2
…
Widthi
An example .gauge file is given below:
3
388869.59
386307.41
383681.45
233696.30
239076.10
245652.34
N
E
S
100
50
200
3.2.20 Rainfall data file (.rain)
This file is used to specify a time-varying rainfall rate and is read when the keyword rainfall
appears in the .par file. When used in conjunction with the routing keyword, the rainfall
routing scheme replaces the shallow water equations with a fixed velocity flow for water depths <
depththresh, reducing model runtime and allowing water to flow over terrain discontinuities
(such as off building roofs) without destabilising the solution (Sampson et al., 2013). The rainfall
term is applied to every model grid cell at each time step to give spatially uniform rainfall over the
domain. The file format is similar to the .bdy file:
Line 1: Comment line, ignored by LISFLOOD-FP.
Line 2: Number of time points at which boundary information is given followed by a keyword for the time units used (either
‘days’, ‘hours’ or ‘seconds’).
Line 3: Value1
Time1
Line 4: Value2
Time2
etc…. …
…
Line i: Valuei
Timei
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Where Valuei is rainfall rate in mm hr-1 and Timei is the time at which this value occurs in the units
specified on line 2. The model then linearly interpolates these values to give the rainfall rate at
each time step.
3.2.21 Checkpointing file (.chkpnt)
This file will be written by the model if checkpointing is on (by specifying the keyword
checkpointing in the .par file). It can be used to restart the model from the time at which the
checkpoint file was saved by a pervious simulation, it includes the internal states and parameters
of the model at the time the checkpoint file was written and will overwrite parameters specified in
the .par file or on the command line.
3.2.22 Start file – water depth (.start)
This file in ARC ascii raster format is used to set initial depths in the model at the start of a
simulation. This option is activated by including the keyword startfile in the .par file and
following this with the name of the file to be read.
3.2.23 Start file – water depth binary (.startb)
This file in binary format is used to set initial depths in the model at the start of a simulation. This
option is activated by including the keyword binarystartfile in the .par file and following
this with the name of the file to be read. The binary data are in double precision except for the first
two numbers in the file which are integers. Numbers in the file should be in the same order as the
ARC ascii raster files, therefore:
Ncols (integer), nrows (integer), xllcorner (double), yllcorner (double), cellsize
(double), NODATA_value (double), depth (doubles of nrows*ncols in length)
These files can be written in the model output by including the keyword binary_out in the .par
file
3.2.24 Startfile – water elevation
This file in ARC ascii raster format is used to set initial water surface elevation in the model at the
start of a simulation, which will be converted to a depth using the DEM by the model. This option
is activated by including the keyword startelev in the .par file and following this with the name
of the file to be read.
4 Setting up a simulation
Setting up a simulation requires generation of the above files populated with appropriate
parameter values. There is no specific order in which to attempt these tasks but the following
series of steps may appropriate in many cases:
1. Generate an appropriate floodplain DEM using a suitable program. Typically this would
consist of high-resolution topography data in some format that is then manipulated to give a
raster grid in the ARC ascii grid format (described in section 4.2.6). Save this as a
.dem.ascii file.
2. If spatially variable floodplain friction is to be specified use a suitable program to generate a
further ARC ascii raster grid of the same dimensions and cell size as the .dem.ascii file and
populate this with appropriate Manning’s n values. Save this as an .n.ascii file.
3. Generate a vector of the channel centre line in the same co-ordinate system as used for the
.dem.ascii file using an appropriate digitising package.
4. Populate the .river file with channel and boundary condition information. Channel data
should come from either site inspection or surveys or historic cross-sectional surveys. If the
latter are used the possibility of geomorphic change should be allowed for.
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5. Assign boundary condition data to the .bci and .bdy files if required.
6. Prescribe weir linkages if required in the .weir file.
7. Define model run time parameters and file names in the .par file.
8. Use the model to generate a set of initial conditions. This may be necessary for certain
dynamic simulations and merely consists of the results file from a previous simulation.
Specify the name of the initial conditions file after the keyword startfile in the .par file.
The model should now be ready for simulations to begin. In addition to this manual there are also
a number of stand-alone exercises available to download. These including all necessary data and
guide users through some example test-cases using lisflood. These are available from
http://www.bris.ac.uk/geography/research/hydrology/models/lisflood/training/.
5 Running a simulation
To run the model, open a DOS or UNIX/LINUX shell and at a command prompt type the name of
the executable file generated by the compiler and the name of the model parameter file. For
Windows this is:
lisflood_win [command line options] model.par
while on UNIX/LINUX:
./lisflood_win [command line options] model.par
Where ‘model’ is the file naming convention chosen by the user (in the case of the example
application given with this code release this is buscot.par). The LISFLOOD-FP source code has
also been compiled for Mac OS in the past. The command line options can be used to turn on
diagnostic information and warnings as the model runs or used to provide override control of
certain model parameters specified in the input files. The latter facility is useful for running the
model in Monte Carlo mode from a batch file as it avoids the need for multiple input file versions.
Command line options implemented to date are given in Table 14 below:
Table 14: Command line options for LISFLOOD-FP.
Option
Description
-v
Verbose mode. With –v turned on the model generates a number of runtime diagnostic
messages.
-version
With parameter file name omitted this option allows the user to check the version number
of the executable.
-gzip
Causes model output files to be compressed on the fly. Note: this option issues a system
command to run gzip at each saveint. Linux only option, ignored in windows. It
assumes you have gzip installed. If not it generates an error but otherwise files are
created ok, just not compressed.
-dir dirname
Gives the directory name for results files. Overrides the name given after the keyword
dirroot in the .par file.
-resroot
Root for naming of results files (e.g. root.op, root.mass, root-0001.wd etc)
-simtime value
Allows the simulation time to be specified in the command line followed by a value for the
simulation time in seconds. Overrides the value given after the keyword sim_time in the
.par file.
-nch value
Implements a spatially uniform channel friction for all channel segments with a value
given in terms of Manning’s n. Overrides the value given in the .river file.
-nfp value
Implements a spatially uniform floodplain friction with a value given in terms of Manning’s
n. Overrides the value given after the keyword fpfric in the .par file or the values given
in the .n.ascii file.
-inf value
Implements a spatially uniform infiltration loss across the whole floodplain with a value
-1
given in ms . Overrides the value given after the keyword infiltration in the .par file.
-weir filename
Gives the name of the .weir file. Overrides the name given after the keyword weirfile
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Description
in the .par file.
-checkpoint
Turns checkpointing on with default features. Code is checkpointed every hour of
computational time by default using the output file naming convention specified in the
.par file after the keyword resroot. See Section 3.2.1. If specified, the interval given
after the keyword checkpoint in the .par file is used. Although this would also switch
on checkpointing anyway making the use of this command line option unnecessary.
-loadcheck filename
Forces program to read in an alternative checkpoint filename at start. Useful for when you
don’t want the start checkpoint file overwritten by the program as it goes along. Also
turns checkpointing on with default features (as option –checkpoint). If specified, the
interval given after the keyword checkpoint in the .par file is used.
-log
Redirects screen output to a log file in the results directory.
-debug
Outputs 3 files; the final dem after burning in the channel and bank mods (*.dem), the
channel mask (*.chmask) and the channel segment mask (*.segmask).
-dynsw
Implements the full dynamic wave steady state initial solution for the 1D diffusive channel
solver
-dhlin value
Overwrites the linearization threshold value for the adaptive version which is currently set
as dx times 0.0002 from Cunge et al., 1980 and Hunter et al., 2005.
-kill value
Forces the model to exit after a given length of computation time (in hours) which is
useful on clusters which put limits on maximum run time.
-acceleration
Switch to use acceleration version of the 2D solver
-cfl
Reset CFL value on the command line for acceleration, Roe and Subgrid version.
Overrides the value given in the .par file. Default value is 0.7.
-theta
Reset theta value on the command line for acceleration version.
given in the .par file. Default value is 1.
-steady
Turn on steady state checking. Simulation will automatically end when steady state is
3 -1
reached – as default this is when Qout matches Qin to within 0.0005 m s
-steadytol
As above but with a user specified tolerance for the difference between Qout and Qin
Overrides the value
The order in which command line options are used is not important. Just remember that the
parameter file is the last argument on the command line.
If the “comp_out” keyword specified, LISFLOOD-FP will output a time to completion estimate to
the screen at every save interval. This is useful when trying to work out when the run will
complete. Times are in minutes, an example is shown below.
T(mins): M: 500.0, C: 5.3, M/C: 94.94, ETot: 17.6, EFin: 12.3
M: model time
C: computer time (real world minutes spent processing)
M/C: Time ratio (In this case, 100model minutes are processed for every
real world minute)
ETot: Estimated total time for run
EFin: Estimated time to completion of current run.
In verbose mode the diagnostic messages are mostly self-explanatory. The exception is:
Smoothing bank cells with tolerance
htol
Where htol is a numeric value in metres. This refers to the operation of the SmoothBanks
subroutine which corrects a potential source of model instability. This subroutine searches
through the floodplain elevations in cells adjacent to the channel and identifies areas of low lying
floodplain that are within a certain vertical tolerance (htol) of the interpolated channel bed
elevation at that point. If found the elevation of the relevant floodplain cells are raised to the sum
of the bed elevation and htol. For the Buscot example, htol is set to the default value of 1 m.
The user can override the default value by using the htol parameter in the .par file.
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By default the model will use all shared memory cores available on the host machine. This is
done by creating parallel threads using a method known as OpenMP (Neal et al., 2009). The
number of cores has no effect on the simulation results except that the model tends to run faster
on more cores. To manually set the number of cores you will need to set the operating system
environment variable OMP_NUM_THREADS to the number of cores you want to use.
5.1 Checkpointing
LISFLOOD-FP has a very useful checkpointing facility. This allows it to write out a file containing
the current state of the model. This file is repeatedly overwritten at a default or user defined
computation time interval. If the program crashes or is killed during the run, this allows the run to
restart from when the last checkpoint write occurred rather than from the beginning again. This
facility is turned on by using the checkpoint option in the parameter file. The default interval is 1
hour computation time. If the user requires a different interval, this number (in hours) should be
placed after the checkpoint keyword.
There is also a -checkpoint command line option, although this does not allow the user to
specify an interval on the command line and uses the default 1 hour. Note, if an interval is
specified using the checkpoint option in the parameter file, this will be used. However, this
makes the use of the command line -checkpoint option superfluous anyway!
If checkpointing is on, then when the model starts it automatically looks for the default file named
“resroot”.chkpnt in the directory from which the model was executed. If it finds the file, it will
assume that it is from a previous partial run and attempt to read it in and then restart from that
point. If it does not find the file it will assume that this is a fresh run and create the file. If you do
not want to restart the run from the checkpoint, just delete the *.chkpnt file.
It is also possible to start the checkpointing from an alternative filename, which does not then get
overwritten by the checkpoint facility. You do this by using the command line option –loadcheck
“filename” or the loadcheck “filename” option in the parameter file. Note, if there is a
default named checkpoint file existing when LISFLOOD-FP starts, it will assume that this is newer
(i.e. later on in the run) than the alternative starting point and load this to start the run. Just delete
the default checkpoint file if you want to start again from your alternative starting checkpoint file.
The loadcheck option switches on the checkpointing by default, so there is no need to also
specify this at the same time, unless you want to dictate a user defined interval.
The checkpointing facility writes a copy of all important variables to a binary file. This saves space
compared to an ascii file and maintains model precision. However, it does mean you may not be
able to use the checkpoint file on a different machine (e.g. Linux then Windows). LISFLOOD-FP
may well crash if the new machine uses a different binary convention (known as little or big
endian). You may also experience a crash if you change some of the run parameters and expect
LISFLOOD-FP to restart from a checkpoint file written with different parameters. LISFLOOD-FP
does do some basic parameter checks when reading in a checkpoint file, such as domain size,
but mostly assumes the basic parameters don’t change. Importantly, if the LISFLOOF-FP version
number or checkpoint version number has changed since the checkpoint file was created, the
code will issue a warning and exit. This is to prevent problems of forward and backward
compatibility.
A checkpoint is made at the end of the simulation as well as during it - this makes it possible to,
for example, run the model in steady state for a period, and then run multiple different
hydrographs from that point - the new hydrograph should include the period of steady state in the
timings.
Important Note: after a checkpoint restart, the output written to the mass file is appended to the
file rather than overwriting the previous lines. A checkpoint break line is added before the new
lines are written, and this will let you see where it started up again, but leads to a discontinuous
mass record. You can manually edit the mass file after the run to remove the overlap if you want
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the data continuous. The stage output file behaves in a similar fashion. Numbered results files
continue to be output at the correct time.
5.2 Output file formats
During a simulation the model produces a series of results files named according to the resroot
convention given in the parameter file. These are placed in the dirroot directory if this keyword
and a directory name are placed in the parameter file. The output files are produced at different
time intervals according to specifications made by the user in the parameter file and are described
below.
5.2.1 Mass balance output file (.mass)
This file gives details of the model mass balance performance and is written at the interval
specified by the keyword massint in the parameter file. There is currently no keyword to
suppress the output of these files. The output consists of 11 columns of data, space separated:
Column 1: Time. The time in seconds at which the data was saved.
Column 2: Tstep. Time step specified by the user (initial time step in the adaptive model) in seconds
Column 3: MinTstep. Minimum time step used so far during the simulation in seconds
Column 4: NumTsteps. Number of time steps since the start of the simulation.
2.
Column 5: Area. Area inundated in m .
3
Column 6: Vol. Volume of water in the domain in m .
3 -1
Column 7: Qin. Inflow discharge in m s .
Column 8: Hds. Water depth at the downstream exit of the model domain in meters.
3 -1
Column 9: Qout. Calculated outflow discharge at the downstream exit of the model domain in m s .
3 -1
Column 10: Qerror. Volume error per second in m s .
3
Column 11: Verror. Volume error per mass interval (massint variable in the parameter file) m .
3
3
Column 12: Rain-Inf+Evap. Cumulative effect of infiltration, evaporation and rainfall over the simulation in 10 m .
5.2.2 Water depths and elevations at time of satellite overpass (.op and
.opelev)
These files consist of a grid of water depths or water surface elevations (in meters) in ARC ascii
raster format for each pixel at the time of each satellite overpass specified using the parameter
file keyword overpass, or overpassfile for multiple outputs (see section 3.2.15). Multiple
overpass filenames will take the format of *-xxxx-T.op or *-xxxx-T.opelev, where *
denotes the resroot given in the parameter file, and x is the xth overpass time given in the
overpassfile. Numbering of overpass times commences at zero.
5.2.3 Channel water surface profile (.profile)
These files give the channel water surface profile at each saveint or overpass time. This is a
text file consisting of eleven columns of data for each channel segment:
Column 1: ChanX – channel segment X location
Column 2: ChanY – channel segment Y location
Column 3: Chainage - distance along the channel thalweg from the upstream boundary in metres.
Column 4: Width – channel width in meters
Column 5: Manning's – channel manning's
Column 6: Slope – channel slope
Column 7: BankZ – Bank elevation in meters
Column 8: BedElev – bed elevation in meters
Column 9: WaterElev – water elevation in meters
Column 10: WaterDepth – water depth in meters
Column 11: Flow – flow in cumecs
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Files saved at each saveint have the filename format *-riverY-xxxx.profile, where *
denotes the resroot given in the parameter file, Y denotes the river number (which will be 0
unless multiple river catchments have been specified using the keyword multiriverfile in the
.par file) and X is the sequential output file number (0000, 0001, 0002 etc.). . Files related to
a single overpass time are named *-riverY-.profile and multiple overpass filenames will
take the format of *-riverY-xxxx-T.profile, where X is the Xth overpass time given in the
overpassfile. Numbering of overpass times commences at zero. These files are not
produced as default and are only output if the keyword profiles appears in the .par file.
5.2.4 Synoptic water depth, water surface elevation files (-xxxx.wd, xxxx.elev and –xxxx.wdfp)
These files consist of a grid of water depths and water surface elevations values in ARC ascii
raster format for each pixel at each save interval (saveint) specified in the parameter file. Units
are in metres. In this naming convention xxxx is the saveint number. –xxxx.wdfp files are
only produced when using the subgrid channel solver and represent floodplain only water depths
(i.e. in cells containing a subgrid channel this is the depth of water above bankfull depth). By
default these output options are turned on but production of each set of files can be suppressed
by putting the logical keywords depthoff or elevoff in the .par file.
5.2.5 Maximum water surface elevation file (.mxe) and maximum water
depth (.max)
These files consist of a grid in ARC ascii raster format of the maximum water surface elevation
(.mxe) predicted by the model for each pixel over the course of the simulation, or the maximum
water depth (.max). Units are in metres. By default these values are the maximum values over
the whole simulation (i.e. over each time step) but if the keyword mint_hk appears in the .par
file then they are the values over each time step for which the .mass file is written to (massint)
instead. Calculating the maximum at the mass interval rather than at every time-step will be
computationally more efficient but less accurate (especially if water depths are changing rapidly
relative to massint). There is currently no keyword to suppress the output of these files.
5.2.6 Time of initial inundation (.inittm), time of maximum depth
(.maxtm) and total time of inundation (.totaltm)
These files consist of a grid in ARC ascii raster format of the time of initial inundation for each
pixel (.inittm), the time of maximum inundation depth in each pixel (.maxtm) or the total time
for which a pixel is inundated (.totaltm). Units are in hours from the start of the simulation. .
By default these values are the maximum values over the whole simulation (i.e. over each time
step) but if the keyword mint_hk appears in the .par file then they are the values over each
time step for which the .mass file is written to (massint) instead. There is currently no keyword
to suppress the output of these files.
5.2.7 Discharge and velocity values (-xxxx.Qx, -xxxx.Qy, -xxxx.Qcx,
-xxxx.Qcy, -xxxx.Vx and –xxxx.Vy)
These files consist of a grid in ARC ascii raster format of the discharge and velocity values at the
cell interfaces in the x and y Cartesian directions. Grids are output at each save interval
(saveint) specified in the parameter file and xxxx is the saveint number. The grids represent
discharge and velocity at the cell interfaces, so for values in the x direction there is an extra
column in the output, while in the y direction there is an extra row relative to the DEM raster.
Discharge units are in cubic meters per second, while velocity is in meters per second. If subgrid
channels are used in the simulation then three additional files are produced: -xxxx.Qcx and xxxx.Qcy (the subgrid channel discharge values in those cells where a channel is present) and
*.Fwidth (the width of flow in the subgrid channel in those cells where a channel is present). By
default these files are not produced and are only output if the keywords qoutput and voutput
appear in the .par file.
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5.2.8 Hazard output files (.maxVx,
.maxHaz)
.maxVy, .maxVc,
.maxVcd and
These files each consist of a grid in ARC ascii raster format containing the value for each cell for
the corresponding variable. By default these files are not produced and are only output if the
keywords hazard appears in the .par file.
The .maxVx and .maxVy files contain the maximum values over the simulation for water velocity
in the x and y Cartesian directions (see vx and .vy files described above). The .maxVc files
contain the maximum values over the simulation for cell velocity which combines velocities at the
cell interfaces in the x and y Cartesian directions. It is calculated as
Vci,j = ([max(Vi-1/2,j , Vi+1/2,j)]2 + [max(Vi,j-1/2 , Vi,j+1/2)]2)(0.5)
(3)
where Vci,j is the cell velocity and the ½ notation denotes a value at a cell interface. The
.maxVcd file gives the value of the water depth in each cell at the time of maximum cell water
velocity. Finally, the .maxHaz file gives the maximum value for the hazard variable over the
simulation. The hazard variable is an estimation of the combined hazard posed by water
velocities and depth and is calculated as
Haz = H * (Vc + 1.5)
(4)
Where H is water depth and Vc is the cell velocity (as see section 6.2.8 above), based on DEFRA
2003.
By default the maximum values for all of these files are calculated over the whole simulation (i.e.
over each time step) but if the keyword mint_hk appears in the .par file then they are the
values over each time step for which the .mass file is written to (massint) instead.
5.2.9 Adaptive time step and flow limiter (-xxxx.QLx and -xxxx.QLy)
values
These files consist of a grid in ARC ascii raster format of the flow limiter values in the x and y
Cartesian directions. Grids are output at each save interval (saveint) specified in the parameter
file and xxxx is the saveint number. By default these files are not produced and are only
output if the keyword qloutput appears in the .par file.
5.2.10 Stage values (.stage)
Text file consisting of water depth data for each stage specified in the stagefile at each time
specified by massint. Also contains location information and bed elevation for stages. By
default these files are not produced and are only output if the keyword stagefile appears in the
.par file followed by the associated stagefile name. Units are in meters.
5.2.11 Debugging files for interpolating channels onto the DEMfile,
modified dem (*.dem), channel mask (*.chmask) and channel
segment mask (*.segmask).
These files provide more information on the structure of the 1D river model after interpolation of
the river vector to the 2D grid. They are in ARC ascii raster format. The modified DEM includes
the channel bed elevations (in meters) in cells containing 1D rivers, chmask is a raster showing
the location of the channels and segmask is an integer raster showing the tributary numbers for
the channels. By default these files are not produced and are only output if the keyword debug
appears in the .par file.
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5.2.12 Debugging files produced when using subgrid channels (*.dem,
*_SGC_bedZ.asc, *_SGC_bfdepth.asc and *_SGC_width.asc).
They are grids of data in ARC ascii raster format giving the value in each cell for each parameter.
Using the subgrid channel method, the dem used in the simulation (*.dem) is identical to the
original input dem. *_SGC_bedZ.asc files contain the channel bed elevation in each cell
containing a subgrid channel, whilst *_SGC_width.asc contains details of the channel width for
each of these cells. The file *_SGC_bfdepth.asc gives details of the calculated bankfull depths
for each cell containing a subgrid channel. These are calculated as dem elevation minus channel
bed elevation if the bed elevation is known, otherwise it is calculated using the specified channel
width, the dem and details provided in the channel parameter file (.pram). By default these files
are not produced and are only output if the keyword debug appears in the .par file. Units are in
meters.
5.2.13 Discharge file (*.discharge)
Text file consisting of discharge data for each gauge specified in the gaugefile at each time
specified by massint. Column one is the time while all subsequent columns are discharges
across sections. Note that these values do not include water in 1D channels, i.e. values
represent floodplain flow only except if subgrid channels are used in which case it is the total of
the floodplain and subgrid channel flow. By default these files are not produced and are only
output if the keyword gaugefile appears in the .par file followed by the associated gaugefile
name. Units are in cubic meters per second.
5.3 Visualising model results
Visualisation and interrogation of results files and other output files is important not just for data
analysis and presentation, but also good way to check the model is acting as you expect and that
there are no errors in the input files. As all of the output files (and input files) are simple, space
character delimited text files they can be opened by or imported into a range of programs from
your favourite text editor to more sophisticated software packages. Below are suggestions of
some programs which have been used in the past.
Water depth results files (.wd) can be viewed as an animation in FloodView.exe, which is
bundled with the model and data files (windows only). Double-click the FloodView icon to open
the program and load results files using File>Open (use the ctrl button to load multiple .wd
files for animation). DEM files can be added to the animation using File>Load DEM. These
options will work using other results files and filename extensions, however, FloodView expects
files to be in ARC ascii raster format and the colour-scale for animations is set for the typical
expected range of water depth values. FloodView is also fairly temperamental and usually likes
things to be done in above order only.
All gridded output data from the model is in ARC ascii raster format and can be easily uploaded
for visualisation and analysis in ARC-GIS software (note – file extensions will need to be changed
to .asc). Alternatively, gridded or tabulated data files are often uploaded for quick visualisation
or graphing into Excel using File>Open, selecting “All Files *.*” and a suitable delimiter.
For more sophisticated data manipulation or visualisation files could be imported into MatLab.
Some code has been written to facilitate quick import of LISFLOOD output files into MatLab and
can be found at https://source.ggy.bris.ac.uk/wiki/LISFLOOD-FP_and_MATLAB.
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6 Appendix
6.1 Weir calculations
In order to correctly represent embankments, weirs and structures the linkage between two given
cells may be represented by a weir flow equation rather than the Manning formulae as shown in
equation 5 below:
Q = CL(2gH)1.5
(5)
where C is the Weir flow Coefficient (default value 1.4), L is weir breadth across channel and H is
the energy head upstream of the weir.
Weir limitations and notes:
Note that currently the weir calc in lisflood uses the water depth rather than energy head
(thus ignoring approach velocity). This is a reasonable approximation for low Fr number
hydraulics. However, you should find it reasonably easy to add the velocity/energy head if
this was important to your model.
The flow across the cell boundary is totally controlled by the weir calculation within the
subgrid channel. There is no floodplain component. This can lead to localised instabilities
around the weir if there are no cells around the weir cell that can carry bypass flow. This
arises as flow may be out of subgrid bank upstream of the weir (and hence on the
floodplain) and then at the weir is force back in the channel and over the weir. We
recommend placing a stage output location upstream and downstream of the weir in order
to check for this if the weir is critical. The code could be changed to allow for the out of
bank flow and this should be straightforward if you wish to do this for your model.
If in doubt build a simple test model of your bridge and ensure you understand how it is
represented and behaving in lisflood-fp. See the testing directory 16 for examples of
bridge testing setups.
The drowned out weir uses a slightly modified form of the weir flow equation, but this has
not been tested fully and we suspect the modular limit implementation is wrong.
6.2 Bridge calculations
Bridges can also be represented explicitly (since version 5.6.5). The aim with the lisflood-fp
implementation of bridges is to allow the hydraulic effects of a bridge (abutments/deck etc.) to be
represented realistically with a few simple parameters. It should be noted here that it is NOT
intended as an engineering tool for detailed modelling of bridge hydraulics. Hydraulic modelling of
bridges can be a complicated subject in itself and a tool such as HEC-RAS may be a more
appropriate choice for such purposes. Currently bridges have only been implemented in the
subgrid channel version. However if you wished to extend the bridge functionality to normal
floodplain flow cells it should be fairly straightforward. Extension of bridges to the 1D diffusive
solver would be more of a challenge.
The bridge modelling method used is the pressure flow method which implements an orifice flow
equation (equation 6) to calculate the flow through the bridge when the bridge deck obstructs
flow:
Q = CdA(2gH)0.5
(6)
where Cd is the Coefficient of discharge for a fully submerged pressure flow (default value 0.8), A
is net area of bridge opening and H is the difference between the energy gradient elevation
upstream and the water surface elevation downstream. This is a widely used method for
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LISFLOOD-FP User Manual
Code release 5.9.6
modelling bridges and is the default bridge modelling method used in HEC-RAS (against which
the LISFLOOD-FP implementation has been tested).
Figure 1: Bridge as implemented in lisflood-fp.
W
db
dus,ds
egus
qb
qus,ds
WLus,ds
A
H
Zr
= bridge opening width
= bridge opening depth
= upstream, downstream depth of flow
= upstream energy grade depth (Vus2/2g) . Bridge approach velocity Vus is calculated from
qus divided by channel area (not bridge area)
= bridge flow
= upstream, downstream flow
= upstream, downstream water level
= bridge open area (W x db)
= orifice head (WLus – WLds + egus)
= upstream depth to opening ratio (dus/db). Zr = 1.0 when water level is at soffit level.
The actual calculation used by LISFLOOD-FP at a bridge location will depend upon the water
level at the bridge. For water levels below the bridge soffit (Zr<1.0), the normal open channel flow
method is used (using the bridge opening flow area not the channel area). For water levels well
above the soffit, the orifice calculation is used. There is a transition zone between the two types of
flow (roughly between Zr 1.0 and 1.5) where a weighted combination of the two flow types is
used. This transition zone is notoriously difficult to model for various reasons (see Hecras
manual). The approach used here is simple and robust and in tests compares well with the HECRAS sluice approach for this transition zone. Typically for a bridge Zr should be specified in
lisflood as 1.5. If the hydraulics approaching/at the bridge are particularly extreme (e.g. Fr>0.75)
you may find extending this to a higher value e.g. 1.7) may provide extra stability at the expense
of accuracy.
Bridge limitations and notes:
For more irregular bridges it is up to the user to distil the geometry to an appropriate
simple representation that can be used in LISFLOOD-FP. For example, if a bridge has
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LISFLOOD-FP User Manual
Code release 5.9.6
piers you can subtract the pier area from the bridge opening area and put the net area
into LISFLOOD-FP.
While a bridge is placed between two cells, in reality, a bridge must be placed in the
centre of 4 contiguous cells. This is because the calculation uses the flow fluxes at the
boundaries of cells 1 and 2 and cells 3 and 4 in order to calculate approach velocities and
hence energy grade. It is also a good idea to ensure that the 4 cells are not part of some
other process such as a boundary or confluence etc.
If in doubt build a simple test model of your bridge and ensure you understand how it is
represented and behaving in LISFLOOD-FP. See the testing directory 16 for examples of
bridge testing setups.
LISFLOOD-FP does not take into account contraction and expansion losses before and
after the bridge. This means that if your bridge width is significantly less that of the
channel, then the head (afflux) upstream of the bridge constriction will be underestimated.
This does not affect the pressure flow calculation, only the open channel flow calculation
when water elevations are below the bridge deck.
There is currently no provision for overtopping of the bridge deck when water elevations
upstream are very high. You can easily extend the LISFLOOD-FP bridge code using the
weir equation for this case if you require this functionality for your model.
7 References and bibliography
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ARONICA, G., BATES, P. D. & HORRITT, M. S. 2002. Assessing the uncertainty
in distributed model predictions using observed binary pattern information
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BATES, P. D., WILSON, M. D., HORRITT, M. S., MASON, D. C., HOLDEN, N. &
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BECKERS, B. & SCHUTT, B. 2013. The elaborate floodwater harvesting system
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BIANCAMARIA, S., BATES, P. D., BOONE, A. & MOGNARD, N. M. 2009. Largescale coupled hydrologic and hydraulic modelling of the Ob river in Siberia.
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LETTENMAIER, D. P. & CLARK, E. A. 2011. Assimilation of virtual wide
swath altimetry to improve Arctic river modeling. Remote Sensing of
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2007. Evaluation of very high-resolution climate model data for simulating
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DANKERS, R. & FEYEN, L. 2008. Climate change impact on flood hazard in
Europe: An assessment based on high-resolution climate simulations.
Journal of Geophysical Research-Atmospheres, 113.
DANKERS, R. & FEYEN, L. 2009. Flood hazard in Europe in an ensemble of
regional climate scenarios. Journal of Geophysical ResearchAtmospheres, 114.
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M. J. A., STANSBY, P. K., MOKRECH, M., RICHARDS, J., ZHOU, J.,
MILLIGAN, J., JORDAN, A., PEARSON, S., REES, J., BATES, P. D.,
KOUKOULAS, S. & WATKINSON, A. R. 2009. Integrated analysis of risks
of coastal flooding and cliff erosion under scenarios of long term change.
Climatic Change, 95, 249-288.
DAWSON, R. J., HALL, J. W., BATES, P. D. & NICHOLLS, R. J. 2005. Quantified
analysis of the probability of flooding in the Thames estuary under
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DE ROO, A., ODIJK, M., SCHMUCK, G., KOSTER, E. & LUCIEER, A. 2001.
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DE ROO, A., SCHMUCK, G., PERDIGAO, V. & THIELEN, J. 2003. The influence
of historic land use changes and future planned land use scenarios on
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Code release 5.9.6
floods in the Oder catchment. Physics and Chemistry of the Earth, 28,
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satellite imagery to support and verify timely flood modelling. Hydrological
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the calibration of hydraulic models using uncertain satellite observations of
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FEWTRELL, T. J., DUNCAN, A., SAMPSON, C. C., NEAL, J. C. & BATES, P. D.
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FEYEN, L., BARREDO, J. I. & DANKERS, R. 2009. Implications of global
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optimization and uncertainty assessment for large-scale streamflow
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HAN, S. C., YEO, I. Y., ALSDORF, D., BATES, P., BOY, J. P., KIM, H., OKI, T. &
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satellite gravity measurements and implications for water cycle parameters
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HORRITT, M. S. & BATES, P. D. 2001. Predicting floodplain inundation: rasterbased modelling versus the finite-element approach. Hydrological
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HORRITT, M. S. & BATES, P. D. 2002. Evaluation of 1D and 2D numerical
models for predicting river flood inundation. Journal of Hydrology, 268, 8799.
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models for urban flooding. Proceedings of the Institution of Civil
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JUNG, H. C., JASINSKI, M., KIM, J.-W., SHUM, C. K., BATES, P., NEAL, J.,
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KUIRY, S. N., SEN, D. & BATES, P. D. 2010. Coupled 1D-Quasi-2D Flood
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LAGUARDIA, G. & NIEMEYER, S. 2008. On the comparison between the
LISFLOOD modelled and the ERS/SCAT derived soil moisture estimates.
Hydrology and Earth System Sciences, 12, 1339-1351.
LEEDAL, D., NEAL, J., BEVEN, K., YOUNG, P. & BATES, P. 2010. Visualization
approaches for communicating real-time flood forecasting level and
inundation information. Journal of Flood Risk Management, 3, 140-150.
LEWIS, M., HORSBURGH, K., BATES, P. & SMITH, R. 2011. Quantifying the
Uncertainty in Future Coastal Flood Risk Estimates for the UK. Journal of
Coastal Research, 27, 870-881.
MASON, D. C., BATES, P. D. & AMICO, J. T. D. 2009. Calibration of uncertain
flood inundation models using remotely sensed water levels. Journal of
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NEAL, J., FEWTRELL, T. & TRIGG, M. 2009. Parallelisation of storage cell flood
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predictive uncertainty in a distributed hydrological model using sequential
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SAMPSON, C. C., BATES, P. D., NEAL, J. C. & HORRITT, M. S. 2013. An
automated routing methodology to enable direct rainfall in high resolution
shallow water models. Hydrological Processes, 27, 467-476.
SAMPSON, C. C., FEWTRELL, T. J., DUNCAN, A., SHAAD, K., HORRITT, M. S.
& BATES, P. D. 2012. Use of terrestrial laser scanning data to drive
decimetric resolution urban inundation models. Advances in Water
Resources, 41, 1-17.
SANYAL, J., CARBONNEAU, P. & DENSMORE, A. L. 2013. Hydraulic routing of
extreme floods in a large ungauged river and the estimation of associated
uncertainties: a case study of the Damodar River, India. Natural Hazards,
66, 1153-1177.
SCHUMANN, G., DI BALDASSARRE, G., ALSDORF, D. & BATES, P. D. 2010.
Near real-time flood wave approximation on large rivers from space:
Application to the River Po, Italy. Water Resources Research, 46.
STEPHENS, E. M., BATES, P. D., FREER, J. E. & MASON, D. C. 2012. The
impact of uncertainty in satellite data on the assessment of flood
inundation models. Journal of Hydrology, 414, 162-173.
THIEMIG, V., PAPPENBERGER, F., THIELEN, J., GADAIN, H., DE ROO, A.,
BODIS, K., DEL MEDICO, M. & MUTHUSI, F. 2010. Ensemble flood
forecasting in Africa: a feasibility study in the Juba-Shabelle river basin.
Atmospheric Science Letters, 11, 123-131.
THIREL,
G.,
NOTARNICOLA,
C.,
KALAS,
M.,
ZEBISCH,
M.,
SCHELLENBERGER, T., TETZLAFF, A., DUGUAY, M., MOELG, N.,
BUREK, P. & DE ROO, A. 2012. Assessing the quality of a real-time Snow
Cover Area product for hydrological applications. Remote Sensing of
Environment, 127, 271-287.
TRIGG, M. A., WILSON, M. D., BATES, P. D., HORRITT, M. S., ALSDORF, D.
E., FORSBERG, B. R. & VEGA, M. C. 2009. Amazon flood wave
hydraulics. Journal of Hydrology, 374, 92-105.
VAN DER KNIJFF, J. M., YOUNIS, J. & DE ROO, A. P. J. 2010. LISFLOOD: a
GIS-based distributed model for river basin scale water balance and flood
simulation. International Journal of Geographical Information Science, 24,
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VILLANUEVA, I. & WRIGHT, N. G. 2006. Linking Riemann and storage cell
models for flood prediction. Proceedings of the Institution of Civil
Engineers-Water Management, 159, 27-33.
WERNER, M. G. F., HUNTER, N. M. & BATES, P. D. 2005. Identifiability of
distributed floodplain roughness values in flood extent estimation. Journal
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