Calculating surface water runoff volume

Question

I'm trying to calculate how much water will runoff of a area through a given point.  I have the DEM of my area and the soil data.  I've already delineated the drainage basin that feeds the pour point and created flow direction and flow accumulation, but now I'm stuck trying to combine that data with the soil data.  Obviously not all of the water will flow through the pour point, most will get absorbed by the ground, but I was hoping to get a rough estimate of the runoff volume at the pour point based on a rainfall total of X inches. Thanks

JAMIESOMMA · Answer

In case this helps someone else who sees this thread, I'm in the middle of doing this too and I'm taking the following approach:

Method: Rational Runoff Method - I am determining the runoff coefficient from a published Rational Runoff Lookup table based on the following characteristics:

* Soil Hydrologic Group: A, B, C, D (I'm treating the A/D, B/D and C/D groups as D for purposes of the Runoff Coeff since I'm looking at peak flow on a watershed basis).  I'm getting this from USDA's Soil Survey data in the muaggattr table and hydgrpdcd column and converting the soil unit polygons in the Watershed context to a 10 m raster with values for each Soil Hydrologic Group.
* Slope Class: less than 2 percent, 2-6 percent, and greater than 6 percent. I'm getting this from the USGS 1/3 arc second DEM (~10 m resolution), calculating Slope, and then reclassifying the slope raster into a Slope Class raster in the above specified ranges.
* Land Cover Class: I've translated these values in terms of the National Vegetation Class System Class code that is used with the USGS Land Cover raster data sets (30 m resolution).  I've taken their text file that maps all raster values to the NVCS Attributes (including the Class code that approximates the land cover types in the Rational Runoff Method table) and imported it to a table and joined this to the Land Cover raster table.

* I'm taking each of the 3 rasters specified above and then will calculate a new Runoff Coefficient Raster based on looking up the Runoff Coefficient from a Runoff_Coeff table based on the raster values of the 3 input rasters.  [This is the part I'm currently researching how best to do-I think the Combine tool will work for this but I not yet done a Join Field operation with multiple join fields]
* This Runoff Coefficient Raster will then serve as the Input Weight Raster for the Flow Accumulation Tool.
* I'll Extract from Points the Flow Accumulation at each Pour Point and then calculate the effective area of rain harvesting based on the area of each cell in the Flow Accumulation raster.  So if 200,000 cells pour in without weighting for Runoff Coefficient, then something less than this would be the count using the Input Weight Raster based on the runoff coefficient for each cell and this would be the effective rainwater harvesting area for the peak flow calculation.

EstherJensen · Answer

Thank you for that link jdollasin it  is exactly what I needed. I have a runoff grid made with this program http://www.dnv.com/services/software/products/sesam/sesamhydrod/wasim.asp by someone in my department. They use the data you mentioned as an input to wasim.

JoanneDollasin · Answer

ok, thanks for extending some helping hands here... 🙂 by the way, If it might help others who come along to this thread,  I've come across with a certain methodology in estimating the streamflow: http://md.water.usgs.gov/posters/flowGIS/index.html... The problem is, there is no such runoff data in my specific area of interest,..whew! I only have the data I've mentioned in my previous post... I wonder how I can make use of my available data and still adopt the same methodology in that link above...Any thoughts? 🙂