WMS:Louisiana DOTD Models Using the SCS Method

Creating an SCS Project

1. Using the WMS Wizard set the project coordinate system to UTM, NAD83, Zone 15
2. With the Microsoft Virtual Earth Utility identify your study area – make sure it is “bigger” than the study area
3. With Web Services download the DEM (1/3 arc Second recommended) and Topo map (aerial photograph too if you want)
   1. You can try to get the land use and soils data from the web services as well. They are currently on the Aquaveo server and there is not an intent to remove them but not a guarantee the will stay.
   2. You can download the land use file(s) from http://www.webgis.com/
   3. You can ask for the Ssurgo data and get an email with an ftp from: http://soildatamart.nrcs.usda.gov/
   4. Read these shapefiles into WMS and be sure they are converted to the UTM, NAD83, Zone 15 coordinate system
   5. If there are problems with the topo map you can go to http://msrmaps.com/ or to http://atlas.lsu.edu/ and navigate to download the DRG Files
   6. For the DEM you can go to http://seamless.usgs.gov/
4. Delineate the watershed.
   1. Turning on the Create TC Coverage is optional
5. Select the HEC-HMS model (you won’t use this but it will line up best with what you want to do for the SCS method).
6. In the Define Land Use option
   1. Join the Ssurgo attributes tables by right clicking on each Ssurgo shape file and choosing the Join Ssurgo Data option
   2. Back in the wizard Create your Land Use and Soils coverage
7. Under Hydrologic Computations in the Wizard.
   1. Compute GIS Attributes to determine the composite CN
   2. In this you will need to load the standard LADOTD SCS table (the current definition for Residential is for ¼ acre lots, you may want to adjust this value or any other as appropriate).
   3. Compute Basin Data and select the Lag Time – SCS equation.
8. You can set up the Job Control and Precipitation data for an HMS model if you want, but it is not necessary.
9. Clean up the model.
   1. Turn off the Model Checker
10. Exit the wizard and identify the data necessary to run your model.
11. Go into the Display Options under Drainage and turn on the Maximum Flow Distance and Maximum Flow Slope.
12. Save your WMS Project
13. Open the SCSRainfall.jpg file.
14. Run your model with the standard LADOTD program.
    1. http://www.dotd.louisiana.gov/highways/road_design/hydr/