Runoff and sediment modeling in a peri-urban artificial landscape: Case study of Olympic Forest Park in Beijing

摘要

In recent years, many ecological parks have been constructed in the peri-urban areas of Chinese cities to relieve the ecological pressure of high-speed urbanization. Compared with the natural landscape, the artificial ecological park is totally a man-regulated system, which is fragile and very sensitive to the runoff and sediment disturbance from severe storms. Thus, a case study was performed in the artificially constructed Beijing Olympic Forest Park to study its hydrological response to severe storms and to identify the critical areas for implementing Best Management Practices (BMPs). The monitored rainfall-runoff data revealed that infiltration excess runoff was the predominant runoff generation mechanism in the study area. A Dynamic Watershed Simulation Model (DWSM) was used to simulate the runoff and sediment transport processes from monitored and design storms. Owing to the complexity of topography and lack of a single outlet, the DWSM was calibrated and validated in a typical hillslope with a nested structure to acquire scale appropriate parameters. Then, the DWSM was applied to other overland segments and scaled consistently to perform scenario analysis under design storm conditions. Results showed that, the shift of rainfall intensity in design storms could produce amplified hydrologic responses, but had little impact on the overland rankings based on runoff depth or specific sediment yield. However, the different spatial patterns between runoff and sediment revealed the spatially varied soil erosion processes (transport-limited or supply-limited) and the necessity of site-specific BMPs. Generally, the areas with high runoff and sediment potentials were mostly related to the segments with small drainage areas and short, steep slopes, while the constructed drainage system could function as interception BMPs to reduce runoff and sediment discharges. The analysis of the relationship between overland rankings and overland features could provide guidance to identify critical areas and to implement site-specific BMPs in peri-urban artificial landscapes.