Instructions

• Introduction
  • Quick start instructions
  • Detailed instructions
    • Useability:
    • Data requirements
    • Catchment mode data requirements
    • Reach mode data requirements
  • Notes on other parameters
    • Grid cell size and resolution
  • CASE STUDIES
    • Reach mode: Modelling the River Severn nr. Caersws, U.K.
    • Catchment example: Modelling the River Swale, U.K.
    • Processing the results

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Introduction

This section contains two sets of instructions: for a 'quick start' and more detailed. Theses instructions were first written for CAESAR version 5.2 but apart from some slight changes in the screenshots should be fine - if there are any errors please let me know. Or, please edit them yourself! it is after all a wiki!! Thanks. Tom.

Though these instructions include a brief overview of what some of the model parameters do, there are details of what the boxes and parameters in each tab are in the 'tabparameters' wiki page: https://sourceforge.net/p/caesar-lisflood/wiki/TabParameters/

These instructions do not explain how the model operates - more how to use it. For this you need to refer to the literature. There are two main papers that deal with how CAESAR-Lisflood works - they are:

Coulthard, T. J., Neal, J. C., Bates, P. D., Ramirez, J., de Almeida, G. A. M., & Hancock, G. R. (2013). Integrating the LISFLOOD-FP 2D hydrodynamic model with the CAESAR model: Implications for modelling landscape evolution. Earth Surface Processes and Landforms doi:10.1002/esp.3478

Van De Wiel, M.J., Coulthard, T.J., Macklin, M.G., Lewin, J. (2007) Embedding reach-scale fluvial dynamics within the CAESAR cellular automaton landscape evolution model. Geomorphology, 90 (3-4), pp. 283-301.

And for some older background material:

Coulthard, T. J. Macklin, M. G. & Kirkby, M. J. (2002) Simulating upland river catchment and alluvial fan evolution. Earth Surface Processes and Landforms. 27, 269-288.

Other publications can be found on the publications page of the wiki https://sourceforge.net/p/caesar-lisflood/wiki/Publications/

There are also a set of video talk throughs using the examples described below: https://sourceforge.net/p/caesar-lisflood/wiki/InstructionVideos/s

Finally - there are many tips, hints and explanations to be found on the CAESAR discussion board: https://groups.google.com/forum/?fromgroups#!forum/caesar-lisflood please look here first before asking any questions - as most things have been asked before!

Quick start instructions

These provide a very quick way to get started with CAESAR-lisflood - allowing you to get up and running with the model in a few clicks. This is probably a good place to start, as from here you can begin to explore what the other parameters do - and use these examples as templates for your own study.

Firstly, download CAESAR-lisflood quick start.zip from the download tab.

20/8/2011 CAESAR quick start guide catchment mode

• Navigate to the folder quick start catchment
• Download the latest .exe of CAESAR-lisflood unzip it and copy it to the folder quick start catchment
• Double click on CAESAR-lisflood.exe
• Click on the menu Config file > open once the program has started
• Select swale1 from the folder quick start catchment and click open (or double click swale1)
• Click load data button (bottom left)
• OK the check box that appears
• Click start – and its working....

For reach mode:

• Navigate to the folder quick start reach
• Download the latest .exe of CAESAR-lisflood unzip it and copy it to the folder quick start reach
• Double click on CAESAR-lisflood.exe
• Click on the menu Config file > open once the program has started
• Select reach1 from the folder quick start catchment and click open (or double click swale1)
• Click load data button (bottom left)
• OK the check box that appears
• Click start – and its working....

Detailed instructions

Useability:

CAESAR is coded in Visual C#, and runs as a windows program on Windows NT, 2000, XP, vista, 7 and 8 - 32 and 64 bit. No programming experience is required in order to use it, and example files can be loaded and the program successfully run in minutes.

Applying it to data sets other than the sample ones described below requires the capability to manipulate and edit DEM files, and the user would require some basic knowledge about data manipulation using (for example) Excel and ArcGIS or equivalents.

The source code for CAESAR is openly available for download under the terms of a GNU licence which prevents it from being sold for profit. The code is presently more than 10000 lines, but there is much duplication, and users with medium programming skills should be quite capable of editing and altering it for their own purpose.

Data requirements

CAESAR can be run in two modes; a catchment mode, with no external fluxes or inputs aside from rainfall; and a reach mode with one or more points where water and sediment are inputted to the system. It can be run in both catchment and reach mode together.

Catchment mode data requirements

For the catchment mode, CAESAR requires rainfall data which ideally shold be hourly, but different time periods (mins to days) has been used. Ideally, the study catchment should have a rainfall record as well as a gauged point or outlet which allows the hydrological component of the model to be evaluated/calibrated. Thereby modelled discharges match the field observed discharges for a given flood. However, if this is not available nearby rain data can be used and there are ranges of example settings from which the hydrological model can be parameterised.

CAESAR also requires a raster DEM (not TIN) for the catchment, and editing and correcting the DEM is an important part of preparing for a CAESAR simulation. The model can cope with a wide range of DEM resolutions, and has been applied with DEMs of grid cell sizes ranging from 1m to 100m. Some DEM’s can be applied in their raw form, but often the data contains errors which can cause the model significant problems, for example an erroneous series of cell elevations can cause an obstruction across a valley floor. It is therefore recommended that DEMS are first processed to remove any sinks or pits, and to ensure that the drainage network follows a straightforward descent to the exit point. This can be carried out simply using the freely available ARC-HYDRO extensions toolkit for ARC-GIS 8.x and 9.

CAESAR is set up so that the water and sediment exit point from the DEM (where sediment and water outputs are measured) must be on one of the edges of the map (This is an important change for versions 1.2 onwards). The model will not route water or allow water to exit from 'no data' cells (those with a value of -9999) so these must be removed from the edge of the DEM where you want flow to exit.

CAESAR accepts DEM data in an ascii raster format which consists of a 6 line header, followed by the grid cell elevations in rows and columns. This is in the same format as data exported from ARC-VIEW, ARC-GIS etc.. using the RasterAscii command or equivalent.

Reach mode data requirements

For the reach model, CAESAR also requires a DEM file in the same format. Again, it is worth taking time to ensure that there are no errors in the DEM. Sometimes, there are individual cells, or groups of cells that may require editing or removing, and for this purpose a useful program called RasterEdit (created by Marco Van de Wiel) is available from the CAESAR website.

As for catchment mode, water must exit directly from ANY edge of the DEM – it will not be routed into -9999 or nodata cells. In reach mode an additional file is required that contains the water and sediment inputs for the reach. These are stored in an ascii file with the time step in the first column, water discharge in the second, and the inputs for the separate grainsize fractions (in m3 for the time step) in the 6th to 14th column. This file is in the same format as one of the catchment output files (see later). CAESAR can also be run in both catchment and reach mode, so for catchments that also contain a point source (for example a major tributary) the model can take both rainfall and point inputs.

Notes on other parameters

CAESAR also requires information on the grainsize distributions for the catchment. It presently takes up to 9 different grainsize fractions and can cope with both bedload and suspended load fractions. The model operates using a variable time step controlled by the amount of erosion and deposition occurring within the catchment. A parameter (erodelimit) is set which represents the maximum amount of erosion or deposition that can happen within any one time step. If this amount is exceeded, the model halves the time step and repeats erosion calculations until it is below this limit. This ensures numerical stability (as too great a time step can lead to excessive amounts of erosion and deposition) and allows the model to have long time steps (up to 1 hour) during periods of quiescence (e.g. low flows) yet have small time steps (<0.1s) during floods or periods of erosive activity.

Grid cell size and resolution

CAESAR can accept any grid cell size in the DEM (though all cells must be the same size) and has been used with DEM’s from 1m to 100m cells. However, choice of grid cell size is important, as there are significant compromises to be made between the area that can be modelled, the resolution, and the time it takes the model to run. CAESAR can run with up to 2 million grid cells, but is probably best suited to applications with 250 000 to 500 000 cells. Quite simply, the smaller the number of grid cells, the faster the model will operate. This is particularly important as increasing the resolution linearly, results in an exponential increase in the number of grid cells. Furthermore, the erodelimit parameter - or the amount that can be eroded or deposited on a cell per iteration - can be contingent on grid cell size. Changes in cell elevation represent changes in local slopes, and a 0.1m change with 1m cells equals a 10% change in slope, yet a 0.1m change in 10m cells equals a 1% change. Thus increasing the grid cell size of the DEM that is being modelled results in a greater than exponential increase in computational time, as changes between grid cells result in less severe alterations in slope. These resolution issues are also contingent upon the time that is required to be modelled. If a single flood is to be simulated, then this can be carried out at a higher spatial resolution that may (for example) take a day to run. If 100 years are to be simulated, this period may contain 300+ floods, and so take 300 days to complete. Extreme examples of model run times include 2 months to simulate 10000 years on a 800 by 200 cell DEM (50m resolution) of the River Swale, U.K. There are many ways in which the model speed can be increased, including parallelisation by dividing a catchment into sub catchments and running these sub catchments simultaneously on separate machines. In addition, the cell size affects the time step of the flow model. This time step is controlled by the courant number, flow depth and the grid cell size. Smaller grid cells will lead to smaller time steps, as flow cannot me moved across more than one cell (in distance) at once. Furthermore, smaller grid cell sizes leads to (as above) greater relative changes in elevation between cells and a smaller courant number may be required in order to maintain numerical stability of the flow model. If you start getting a checkered pattern for your flow depths, either the courant number is too high, erodelimit is too high or both.

CASE STUDIES

In the following section, two examples shall be demonstrated. Firstly an example of CAESAR operating in reach mode, simulating erosion and deposition on a 2km section of the River Teifi, near Lampeter, U.K. Secondly, a catchment example for the River Swale, U.K. Both examples are found in the quickstart examples described above and found in the downloads section above.

Reach mode: Modelling the River Severn nr. Caersws, U.K.

This example is for a c.2km by 2km section of the River Teifi, immediately downstream from Lampeter, Wales. The DEM is at 10m resolution and created from downgraded LiDAR data. To run this example, download the relevant files which include the main program file (Caesar 5.1.exe) and the sample data files teifi.zip and swale.zip. Unzip and place them all in one directory.

The three files to be used for the Teifi example are highlighted in Figure 3. They are whole9.txt (the DEM file) input2.txt the water and sediment input data file and teifi1.xml - the configuration file.

Figure 3.

To run the CAESAR model itself, double click on the Caesar .exe file and after a few seconds the main start up page of CAESAR will come up (Figure 4). This contains a series of tabs, that contain groups of checkboxes and buttons that allow you to alter the parameters for the model. The explanation for all these parameters is too long for this brief guide, but will be prepared in to a technical appendix for the model. In short, each tab contains the parameters for different sets of processes and parameters - files, hydrology, the DEM, input points etc..

Figure 4.

Click the config file menu and open, then navigate to the folder where the downloaded files are, and open the configuration file teifi1.xml. This will load in a set of default parameters for the Teifi example. If you change any of the parameters within the set up screens, you can save them as a configuration file, which allows the easy set up of the model.

To run the model simply click the large load data button, then when the data has loaded, the start button to the right will be highlighted. Click this and the program will start. It takes a few seconds to initialise the data and to go through some initial scans - in order to define the area where the hydraulic model will operate. After this wait, figures at the base of the window should start to change. These indicate the number of iterations the model has carried out, the modelled time, the water discharge exiting the model (at the right hand edge) and the volume of sediment being eroded for each time step. Whilst the program is running, the menu at the top of the screen allows the user to save the configuration parameters as a config file, and also to change the display options. There are two menu’s of display options, that allow the user to display a shaded relief map of the DEM, water depth, erosion and deposition that has occurred since the model started, grainsize, shear stress, velocity etc.. Figure 5 illustrates the Teifi reach example showing the DEM in the background with water depth (a) and erosion and deposition (b). The final menu group controls the files that are saved by the model. The elevations, grainsize data, water depths and other parameters (that are listed on the menu) are automatically saved every 100 iterations. This allows the model to be re-started from the point at which it was last running (e.g. if the computer is switched off) by using the elevation and grainsize data as starting data for the new run. Processing the output data is covered further on in this section.

Figure 5. Screen showing water depths (left) and changes in elevation (right: red is erosion, green is deposition)

To simulate a flood, we can alter the discharge in the input file. Open the input file (called input2.txt) in a text editor (e.g. Notepad) and edit the second number in the first line from 10 to 120 - and re-run the model again. This alters the input discharge for the first period of the models run from 10 to 120 m3s-1 which causes the channel to flood, as shown in the right hand frame of Figure 6. This demonstrates how the input file could be a gauged record and a series of flood events could easily be run through the model. The parameters in the start up screen allow the user to specify many options, including changing grainsizes, slope failure thresholds, alterations to the flow model, how shear stress is calculated, which input files are used, what and when output files are saved. There is also the option to record the visual output as an .avi movie file.

Figure 6. Input file, highlighting first discharge input point and the corresponding inundation areas caused by raising that value from 10 to 120.

This example demonstrates how rapidly CAESAR simulates channel and floodplain flow patterns, as well as how it models fluvial erosion and deposition. If model runs are continued, then the erosion and deposition patterns can change, and provide results as illustrated in Figure 7, where there has been erosion and deposition within the channel, the deposition of overbank fines and the development of channel bed armour.

CAESAR is capable of modelling larger reaches and in more detail. This basic example is to demonstrate how the model is relatively straightforward to set up and run, and to give an indication of what sort of results it can generate in reach mode.

Figure 7. Image showing the section of the River Teifi modelled in Figures 5-7. This illustrates erosion and deposition within the channel and flooplain, with the lower left hand image showing the D50. The right hand frame shows changes in the D50 across the cross section marked on the left hand image, as well as elevation changes that occurred during the simulation.

Catchment example: Modelling the River Swale, U.K.

This example is for the a 40 by 10km catchment area of the River Swale, Yorkshire Dales. For this much larger area the DEM is of 800 by 200 50m grid cells. This example runs with the other sample files downloaded in the quick start examples. The files used to drive the catchment simulation are different, instead of an input file, the simulation uses an hourly rainfall data set, that comprises of a text file with the hourly rainfall rate in mm on each line. To run this example, again double click on the Caesar .exe file and from the config-file menu open the configuration file swale1.xml. As this run is operating in catchment mode, the user has to uncheck to reach mode box and check the catchment mode box, as shown in Figure 8.

Figure 8.

Then, as for the previous example, click load data, and then start when the start button becomes highlighted. This will take longer to start than the previous reach example, and this is due to the DEM containing 4 times the number of grid cells. When the model begins to operate, a small part of the drainage network should appear, as shown in Figure 9. This is only a fraction of the total network, and examining the water discharge figures (3rd box from the left on the bottom info panel) there is only a discharge of 1.3m3s-1. This is very small for a 400km2 catchment, and this is due to the hydrological model only having received a small volume of rainfall. The catchment is in effect in drought conditions. After approximately 23 days, a significant rainfall event occurs in the rainfall data set, and this causes the discharge to increase, and the drainage network to expand, as shown in Figure 10. This is a very modest event for a catchment of this size (only 20m3s-1) but it illustrates how the hydrological model interacts with the catchment drainage network.

Figure 9. Initial drainage network for the Swale catchment simulation

Figure 10. Expanded drainage network, due to rainfall event. As per the reach example, when running in catchment mode CAESAR can produce output for elevations, surface grainsize, water depths etc.. selected using the options in the save options menu. Importantly, as mentioned previously, both of these examples are rotated so that the main water outflow is at the far right hand edge of the DEM.

Processing the results

CAESAR generates data in two forms. Tables of ascii data that can be readily imported into ARC-GIS for the spatial data (e.g. elevation, water depth, grainsize) and an output file containing the water and sediment discharges output by the model at the right hand edge of the DEM. The format of the data is illustrated in Figure 11, and comprises of a 6 line header then the spatial data (e.g. elevations as in Figure 11) as the value for each grid cell arranged in rows and columns. This is simply imported into ARC-GIS or ARC-View using import to ascii options (asciiraster) and can then be manipulated or displayed in any way required, as shown in Figure 12. Typical analyses include cutfill (subtracting a DEM from one time from a DEM from another) that indicates spatial patterns of erosion and deposition.

Figure 11. Example of the text output files generated by CAESAR

Figure 12. Water depths draped over the DEM for the River Teifi example, created in ARC-SCENE.

By checking a box on the opening screen, CAESAR can also output the water and sediment discharges into a text file at a specified interval (e.g. hourly or daily). This allows the user to plot up the data and record the modelled hydrograph, as well as the sediment discharges for all the nine grainsizes. This data is output in the same format as the data used as input files when CAESAR runs in reach mode, as shown in Figure 6. This allows CAESAR to be set up in a unique way, where a catchment CAESAR run can generate water and sediment discharges for a river catchment at a coarse resolution (e.g. 50m). These data can be saved as an output file, then be fed into a higher resolution reach mode CAESAR model to simulate (for example) a study reach, or area of interest.

In addition, CAESAR will output the image on the screen as a .png image file if you press the ‘graphic to google earth button’. This will also generate a .kml file, and if your DEM is correctly geo-referenced it will display your image in the correct location in Google Earth. The option also exists to create google earth animations based on series of these images stored in a folder ‘animation’.

[Marc MANYIFIKA]

Hi Caesar-Lisflood. In your instructions you are mentioning a quick start zipped file to be downloaded in the download tab but I can not see that tab. Is there any way you can help me get that folder so that I start using the tool? thank you

[Anonymous]

It's in the files tab.

On 15 May 2016, at 18:40, Marc MANYIFIKA bmgz07@users.sf.netamp#98;amp#109;amp#103;amp#122;amp#48;amp#55;amp#64;amp#117;amp#115;amp#101;amp#114;amp#115;amp#46;amp#115;amp#102;amp#46;amp#110;amp#101;amp#116; wrote:

Hi Caesar-Lisflood. In your instructions you are mentioning to a quick start zipped file to be downloaded in the download tab but I can not see that tab. Is there any way you can help get that folder so that I start using the tool? thank you

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[Anonymous]

Its in the file tab...

[Anonymous]

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