Hi Marco -
I’m not sure how FutureWater is packaging their data nowadays (I received it a year ago), but mine contains an already-prepared layer called Hydrologic_Soil_Group.tif - does yours have this layer?
If so, this raster has values of 1/2/3/4/14/24/34. The model requires only values of 1/2/3/4, so you would first need to combine any values of 14, 24 or 34 into one of the allowed values. The USDA has this advice for that:
For soils in groups A/D, B/D, or C/D, the first letter applies to the drained condition and the second applies to the undrained condition. Which single group to use may depend on the area in question. For example, on a watershed basis, group D would likely be the best choice. On the other hand, for a specific site or field, the appropriate choice of hydrologic soil group would depend on whether or not the site has been drained.
Once you have a raster with values only 1/2/3/4, that is (I believe, if it’s like our Seasonal Water Yield model - @dave? ) the layer that goes into the model. This raster will be combined with the CN values in the biophysical table to compute runoff. For example, CN_A in the biophysical table corresponds with the Curve Number for the combination of each land cover type + hydrologic soil group A (which = value 1 in the raster, I’m not sure why we do 1 in the raster and A in the table, the Seasonal water Yield model does as well, it’s confusing.)
I’m interpreting the Urban Flood guide as giving guidance for creating the Hydrologic_Soil_Group raster if you don’t already have it provided (like FutureWater does), but need to create it and do have hydraulic properties data. Personally, I’m confused about the reference to FutureWater’s data, since hopefully they still provide Hydrologic_Soil_Group.tif, in which case you shouldn’t need to do the translation provided in the table you reference.
Hopefully I haven’t just made things more confusing. If anything I’ve said is incorrect relative to the Urban Flood model, someone please correct me!