Effects of the Gully Land Consolidation Project on Runoff and Peak Flow Rate on the Loess Plateau, China

The Gully Land Consolidation (GLC) project, aiming to create land for agriculture on the Loess Plateau, heavily interfered with the underlying surface and thus affected the hydrological process. The purpose of this study was to investigate the effects of the GLC on the surface runoff and peak flow rates of watershed on the Loess Plateau under different rainfall events and hydrological years. A GIS-based Soil Conservation Service Curve Number (SCS-CN) model was used. The results showed that GLC reduced the mean event surface runoff by 6.2–24.7%, and the reducing efficiency was the highest under light rain events. GLC also decreased annual surface runoff, and the reducing efficiency was 12.04% (normal year) > 7.63% (wet year) > 4.45% (dry year). In addition, GLC decreased the peak flow rate of the watershed by 8.1–30.2% and prolonged the time to peak flow rate. The efficiency of GLC in reducing the peak flow rate was higher under light rain events than that under extraordinary storm events. The reason for the decrease in runoff and peak flow rate after GLC was that the GLC decreased the slope gradient and hydrological connectivity of the watershed. The results will provide guidance for the application of GLC on the Loess Plateau and watershed management for similar regions