Dears
I have to assess cadastral level potential soil erosion by using RUSLE model. In view of that, I need HSG map of a study village. I need a scientific methodology to construct soil map.
You can fallow the instruction of the NRCS-CN model to prepare the HSG
that the best and the accurate strategy to prepare the HSG at large scale
Hello
See these sites
www.owp.csus.edu/LIDTool/.../SoilHydGrp.p
www.nrcs.usda.gov/wps/PA.../download
www.nrcs.usda.gov/wps/portal/nrcs/.../soils
www.geoinfo.utm.my/jointgeoinfo2015/download/JIGCabstractBook.pdf
I have not tried to join Soil Hydro Groups with RUSLE equation factors, but each soil group should have slope, K factor. Slope length L is the distance from the topographic divide to observable erosion. The RUSLE applies a rainfall runoff factor that is an energy factor generated by storms and relative to runoff. The C factor is the cover associated to land use and practices of management. Also the P factor relates to erosion control practices used such as BMPs to limit erosion. Each RUSLE factor is part of the overall equation, and you could develop GIS layers of each RUSLE factor or in some instances combine factors such as slope and slope length in a georeferences format (map). After you get all the layers, you could then intersect the layers to multiply the RUSLE factors to obtain the erosion estimate, which could then be color coded by classes of severity as you see fit to present to your audience or research group. Remember that the RUSLE estimates soil loss or surface erosion, and does not address concentrated flow erosion such as rills and gullies. You might also want to want to consider the WEPP (Water Erosion Prediction Project) Model and tools on the internet. I think the GIS (ArcMap) is a good format to consider for making complex georeferenced maps such as you are planning.
Main question is: what kind of soil data do you have? For K derivation you need at least percentages of main textural classes and organic matter. Some national methodologies contain K values assigned according to soil type.
Developing a soil HSC layer are that scale depends on upon soil data you have. If no soil data is available, a soil sampling plan that covers all soil types could be used to develop your data. This data could be pulled into GIS and interpolated to create data for your village using interpolation methods. Drainage class could be decided based on the extent of variability in your soil drainage potential. Standard classes are A to D with additional classes and subdivision depending on the region. A good start is to find the extent of regional variability in HSG using FAO Harmonised global dataset which is very coarse scale but provides some general idea of regional variability.
Mapping soil requires sampling from your area and then interpolation. There are different software to conduct interpolation such as Golder Software Surfer. However, first check if your study area covered by the regional project (SOTER) and the International Soils References and Information Center (ISRIC). If your area is covered you just have to download the data.
You may need to know at least textures of soils of interest, and then you can derive the physical characteristics of the soils from the texture information using pedotransfer functions. HSG is not related to RUSLE but CN.
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