Temporal and Spatial Variations of Extreme Precipitation and Flood Thresholds in Qinghe Basin in Beijing, China

摘要

Extreme weather frequently causes torrential rains and flooding in modern cities, e.g., Beijing, which are much sensitive and fragile to flooding disasters because of high population density. In this study, we aimed to quantify the temporal and spatial distribution of extreme precipitation in Qinghe Basin in Beijing and to develop optimal flood management thresholds by using precipitation records from 1986 to 2014 in two sites of the region. The time that maximum precipitation occurs in a year differed temporally and spatially and mainly concentrated in July and August. Extreme precipitation amount covered 41.7% of total precipitation in a month during flood season. Rain days of rainstorms were on average 1.7 d and 87% of them concentrated in July and August and were more in upstream than that in downstream. Precipitation intensity (SDH) during flood season was on average 11.7 mm d~(-1) and highest (15.1 mm d~(-1)) in July. SDII during critical flood control period increased in upstream during recent 30 years and implied a high flood risk in the future. The spatial distribution of precipitation intensity was significantly different. Our results at basin level would help city authorities designing optimal flood control constructions, drainage facilities, and warning systems.