Fig. 2. Maps of the West Nishnabotna and South Fork watersheds, showing surrogate delineations for highly erodible land (HEL) based on erosion index (E, defined by Eq. [3]) values, and for hydric soils based on wetness index (W, defined by Eq. [2]) values. These delineations have accuracies ranging from 66 to 74% (see Table 6).