WMS:Texas Department of Transportation

WMS Modeling Tips for Texas Department of Transportation

Coordinate Systems

The state of Texas is divided into several State Plane zones. Within each zone, there is an additional surface adjustment factor for each county within the zone. The surface adjustment factors for each county are shown in this pdf file

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. The parameter computed by WMS that corresponds to the Main Channel Slope required by the regression equation is called "Maximum Flow Slope (MFS)"
3. Mean Annual Precipitation: Derived from a map located at the TNRIS website. You can also download the shapefiles directly from here. The shapefiles were developed from a PRISM rainfall grid of mean annual rainfall in the United States. For WMS applications, the raw PRISM data is preferred over the polygon shapefiles which were derived from this data. Mean annual rainfall grids cropped to the state of Texas are available below. The grids contain mean annual precipitation for the hydrologic period of 1981-2010. The grids have been projected into each of the (5) Texas State Plane zones and can be downloaded directly from the links below. Rainfall depths have been converted to inches.
   • Mean Annual Rainfall, State Plane Zone 4201
   • Mean Annual Rainfall, State Plane Zone 4202
   • Mean Annual Rainfall, State Plane Zone 4203
   • Mean Annual Rainfall, State Plane Zone 4204
   • Mean Annual Rainfall, State Plane Zone 4205
   • NOTE: Each zip archive contains an ASCII grid file (.asc) and a projection file (.prj). You can open the file in WMS by selecting the Terrain Data Module to make it active, and 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. Links to the map in each of the (5) Texas State Plane zones are included below.
   • OmegaEM Residual Map, State Plane Zone 4201
   • OmegaEM Residual Map, State Plane Zone 4202
   • OmegaEM Residual Map, State Plane Zone 4203
   • OmegaEM Residual Map, State Plane Zone 4204
   • OmegaEM Residual Map, State Plane Zone 4205
   • NOTE: The zip archives contain an image file (.jpg) and a world file (.jpw) and can be opened in WMS using File | Open and opening the .jpg file

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 at the Compute GIS Curve Number page in the "NRCS Curve Numbers (CN)" section. The sample curve number table for vector land use data can also be downloaded here. The sample curve number table for gridded 2006 NLCD land use data can be downloaded here.