Rainfall erosivity mapping over mainland China based on high-density hourly rainfall records

Rainfall erosivity quantifies the effect of rainfall and runoff on the rate of soil loss. Maps of rainfall erosivity are needed for erosion assessment using the Universal Soil Loss Equation (USLE) and its successors. To improve erosivity maps that are currently available, hourly and daily rainfall data from 2381 stations for the period 1951-2018 were used to generate new R-factor and 1-in-10-year event EI30 maps for mainland China (available at https://doi.org/10.12275/bnu.clicia.rainfallerosivity.CN.001; Yue et al., 2020b). One-minute rainfall data from 62 stations, of which 18 had a record length > 29 years, were used to compute the true rainfall erosivity against which the new R-factor and 1-in-10-year EI30 maps were assessed to quantify the improvement over the existing maps through cross-validation. The results showed that (1) existing maps underestimated erosivity for most of the south-eastern part of China and overestimated for most of the western region; (2) the new R-factor map generated in this study had a median absolute relative error of 16% for the western region, compared to 162% for the existing map, and 18% for the rest of China. The new 1-in-10-year EI30 map had a median absolute relative error of 14% for the central and eastern regions of China, compared to 21% for the existing map (map accuracy was not evaluated for the western region where the 1 min data were limited); (3) the R -factor map was improved mainly for the western region, because of an increase in the number of stations from 87 to 150 and temporal resolution from daily to hourly; (4) the benefit of increased station density for erosivity mapping is limited once the station density reached about 1 station per 10 000 km(2).

Automated summary

This study generated new R-factor and 1-in-10-year EI30 maps for mainland China using hourly and daily rainfall data, and assessed their improvement over the existing maps. The results showed significant improvement in the new maps for the western region and some improvement for the rest of China. The study also found that increasing station density can improve the accuracy of erosivity mapping, but the benefit becomes limited once a certain density is reached.