By-Pixel SVI – Soils Data for Dominant Component Tool

Feedback from conservation planners has suggested that inclusion of slope derived from high-resolution elevation data sources rather than the SSURGO database would improve the applicability of SVI outputs at a local level. For watershed planning purposes, and for individual field evaluation, the SVI produced more useful results by using slopes derived from a 10m DEM than from the SSURGO representative slope.

The Soils Data for Dominant Component tool generates a table containing required soil attributes to calculate an SVI classification using a pixel-based approach. Only a single component per map unit will be included in the table and represents the component with the highest representative percent containing valid data for the three primary SVI parameters (hydrologic group, KW factor, and representative slope).

For instances of consociations, the component with the highest representative percent will be included in the table. There may be instances where no components contain valid input data for the required SVI parameters, and therefore the map unit will be excluded from the table. Secondary SVI attributes (isOrganic, isDrained, and karstSoluble) will be listed as a 0 (condition is not present) for instances of null data or if the condition could not be determined.

Three pixel-based SVI tools are included in the ACPF and are designed to be run in sequence. The ACPF provides an optimal platform for the integration of SSURGO soils data with slope derived from a high-resolution DEM. The non-spatial characteristic of soil components, however, prevents sub-map-unit scale information from being combined with high-resolution topographic information. To combine these disparate datasets with mismatching spatial scales, soil properties associated with the dominant component of each map unit are assumed for the entire spatial extent of the map unit, then combined on a pixel-by-pixel basis with a slope raster derived from a high-resolution DEM. This data integration allows for the generation of SVI vulnerability surfaces at a resolution equal to that of the input DEM, enabling landscape characterization to occur at scales other than the soil map unit.

NOTE: As only a single component will exist per map unit in the output table, this table may be joined to your gSSURGO raster for mapping purposes using “mukey” as the join field.