WMS:Texas Department of Transportation

WMS Modeling Tips for Texas Department of Transportation

NSS

The TXDOT Regression Equation for watersheds in rural areas is listed in the NSS program as "Peak Rural Statewide 2009 5087". The equation requires the following parameters:

1. Drainage Area: Computed by WMS
2. Main Channel Slope: Computed by WMS, currently needs to be transferred manually from basin data parameters to NSS window.
3. Mean Annual Precipitation: Derived from a map located at the TNRIS website. You can also download the shapefiles directly from here. A mean annual rainfall grid for the state of Texas has been developed from this map and can be loaded directly into WMS.
   • UTM Zone 14 file (the file is called meannual.asc and can be opened in WMS by selecting the Terrain Data Module to make it active, and selecting clicking File | Open and changing the file type to "Rainfall Depth Grid (*.*)")
   • UTM Zone 15 file (the file is called meanannual15.asc and can be opened in WMS by selecting the Terrain Data Module to make it active, and selecting clicking File | Open and changing the file type to "Rainfall Depth Grid (*.*)")
4. OmegaEM residual from 2009 5087: Derived from a map located in this report. A link to the report is also contained on the USGS Documentation Site for NSS. The map in this report has been saved as an image file and georeferenced so it can be opened directly in WMS.
   • UTM Zone 14 file (the files are called OmegaEM.jpg and OmegaEM.jgw and can be opened in WMS using File | Open and opening OmegaEM.jpg)
   • UTM Zone 15 file (the files are called OmegaEM.jpg and OmegaEM.jgw and can be opened in WMS using File | Open and opening OmegaEM.jpg)

TR-55

The TR-55 method uses a Curve Number to determine watershed losses. A sample curve number table for use with WMS is located [here]