Hydrometeorological Analysis of Two Flood Events in Qiongjiang River Basin
Analyses and descriptions of the hydrometeorological conditions that contributed to two flood events in the Qiongjiang River Basin from 3 to 5 July 2012 (“7.4”) and from 30 June to 1 July 2013 (“6.30”) are presented. The digital elevation model (DEM) is used to extract the distribution network of Qiongjiang River and its distance to the outlet, and the standard time distance objectively reflects the temporal and spatial distribution of precipitation (especially severe precipitation). Composite reflectivity mosaic from SWAN suggests that the heavy precipitation is caused by multiple extreme rainfall bands in both of the flood events, and the convective systems mainly initiates in the headstreams of the right tributaries moving northeastward slowly down the tributaries and producing flood overlap in Qiongjiang River stem. Since basin wide severe radar echo persists over the Qiongjiang River Basin for about 16 h, serious flood overlap is significant in the “6.30” case, resulting in the flood overflowing in the bank and forming a large area of flood detention basin. When the flood gets to downstream and returns to the river channel, the runway gets narrowed, so the flood peak time at the Taian Hydrological Station is late.