What is the method for computing rasters of total rainfall of a given month, flow accumulation, and land use (runoff coefficient) or soil K factor? I am using ArcMap 10.
In some cases you will be computing and others you simply need to obtain the data.
- Rainfall: you will need these as input rasters by month. Do you have this data? You could check out NOAA http://www.cpc.ncep.noaa.gov/products/GIS/GIS_DATA/
- Flow Accumulation: This should be calculated off of a flow direction grid using Spatial Analyst. Flow direction is based on elevation. Do you have a DEM for your area, preferably high resolution? http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//009z00000051000000.htm
- Land use / runoff coefficient / soil K factor: I'm guessing you have a land use raster and the associated coefficients for different uses?
If you want to calculate rainfall rasters for yourself you should have enough point-sample data and profound knowledge of interpolation techniques like spline interpolation or kriging. Therefore I would use data from NOAA instead as they are more reliable. If the resolution of these rasters is too coarse you may want to try a hybrid between interpolation and already available data.