3.3 Potential Maximum Retention and Erosion
Estimation of CN values is crucial for analyzing retention and SY; thus, this study used a geographic information system to integrate land use and hydrologic soil group data to estimate the spatial distribution of CN values (Figure 10). The higher the CN value, the greater the potential of the runoff in a location, and vice versa. Figure 10 shows that relatively high CN values were mostly distributed in water bodies, buildings, wasteland, and upland fields.
In addition, the spatial distribution of CN values could be incorporated into Eq. (3) to estimate the potential maximum retention. Figure 11 shows that areas with relatively large retention values were distributed in forests, indicating that forest areas exhibited favorable retention potential. The analytical results of the curves of potential maximum retention and SY showed that the curves could be divided into two types according to the cumulative rainfall. For high cumulative rainfall, SY=13764S–1.133 was applicable, whereas for low cumulative rainfall, SY=473.64S–0.866 was. Equation (6) could be used to estimate the spatial distribution of the potential maximum erosion volume (A) in the two aforementioned scenarios (Figure 12). Figure 12 shows the spatial distribution of potential maximum erosion values under cumulated rainfall ranges of (a) 197.2–754.4 mm and (b) 754.4–1419.7 mm.