User guide to floodplain and terrace extraction using LSDTopoTools

If you haven’t run our vagrant setup, you need to clone the repository. First navigate to the folder where you will keep the GitHub repository. In this example it is called /LSDTopoTools/Git_projects/. To navigate to this folder in a UNIX terminal use the cd command:

You can use the command pwd to check you are in the right folder. Once you are in this folder, you can clone the repository from the GitHub website:

If you don’t want to use git, you can download a zipped version of the code:

Before the floodplain/terrace extraction algorithm can be run, you must create a channel network for your DEM. This can be done using the channel extration algorithms within LSDTopoTools. There are several channel extraction algorithms which you can choose from: for more details please refer to the channel extration section. Once you have run the channel extraction algorithm, you must make sure that the csv file with the channel head locations is placed in the same folder as your DEM.

If you are computing floodplains you might want a fancy channel extraction algorithm (like Driech or the Wiener method, see the channel extraction documentation), but for terraces you really are only going to need to pick up the big channels and you can get those with threshold drainage area. So you may with to save some time by extracting channels with this method for terrace studies.

Before we can run the floodplain/terrace extraction algorithm, we need to calculate the correct window size for calculating slope across the DEM. This is used to calculate the thresholds for floodplain/terrace identification. Please refer to the selecting A window size section for information on how to calculate a window size for your DEM. We suggest a value of around 6 m for 1 m resolution DEMs, and a value of 15 m for 10 m resoluton DEMs.

We have also provided some examples parameter files that are used to run the floodplain delineation. You can get the example floodplain driver using wget:

This should be placed in the same folder as your DEM and the channel heads csv file. The example from Mid Bailey Run is called LSDTT_floodplains.param and should look like this:

You can run the analysis on the Mid Bailey Run DEM using the example parameter file, and modify it as you wish for your own DEM.

The table below explains the function of each of these parameters:

Navigate to driver_functions_Floodplains-Terraces directory in the folder LSDTopoTools_FloodplainTerraceExtraction:

You have already compiled the code, so you can just run the program with:

For our example, the command would be:

Before the code can be run, you must compile it. To do this you need to go to the driver_functions_Floodplains-Terraces directory in the folder LSDTopoTools_FloodplainTerraceExtraction. Navigate to the folder using the command:

and compile the code with:

This may come up with some warnings, but should create the file get_floodplains.out. You can then run the program with:

For our example, the command would be:

We have also provided two example files that are used to run the terrace extraction. The first is a parameter file that is used to run the code, and the second is a csv file with the latitude and longitude of two points on the Eel River. You can get the example files using wget:

Make sure that these files are stored in the same place as the DEM!! This should be in the folder /LSDTopoTools/Topographic_projects/Eel_River/

You need to run the channel extraction tool on the parameter file eel_area_threshold.driver. This will result in some channel network files, one of which will be a channel heads (or "sources") file: Eel_River_DEM_ATsources.csv.

In order to run the terrace extraction code you must first create a parameter file for your DEM. If you have been following this tutorial, you should have downloaded an example parameter file for the Eel River DEM and placed this in the same folder as your DEM and the channel heads csv file. The example from the Eel River is called LSDTT_terraces.param and should look like this:

You can run the analysis on the Eel River DEM using the example parameter file, and modify it as you wish for your own DEM.

The table below explains the function of each of these parameters:

To run the code, you need to provide a CSV file with two pairs of coordinates which specify the upstream and downstream points between which you want to find the terraces. The easiest way to do this is on Google Earth.

We have written the code so that it will take the coordinates in latitude and longitude and automatically convert them to the same UTM zone as the DEM - you don’t need to do this yourself! If you are following the tutorial for the Eel River site, then you should have downloaded the file Eel_River_DEM_coordinates.csv and placed this in the same folder as your DEM. For example, the Eel River file has the following structure:

Navigate to the folder driver_functions_Floodplains-Terraces directory in the folder LSDTopoTools_FloodplainTerraceExtraction:

You have already compiled the code, so you can just run the program with:

For our example, the command would be:

Before the code can be run, you must compile it. To do this you need to go to the driver_functions_Floodplains-Terraces directory in the folder LSDTopoTools_FloodplainTerraceExtraction. Navigate to the folder using the command:

and compile the code with:

This may come up with some warnings, but should create the file get_terraces.out. You can then run the program with:

For our example, the command would be: