Radar Quantitative Precipitation Estimation for the Identification of Debris-Flow Occurrence over Sichuan Region in China

Sichuan province is located in the southwest of china. The terrain of Sichuan province is fairly complex.. The east and middle of Sichuan is a basin. The west of Sichuan is high mountain area where the terrain height increases sharply transitioning to the Tibet plateau.. This complex terrain has resulted in several natural disasters including landslide and debris flow due to flooding. There have been lot of casialities and extensive property damage, especially between 2012 to 2014.

This paper focuses on the evaluation of radar based estimates for the identification of debris flow occurrence over Sichuan Region. Observations from three S-band weather radars and rain gauge data are analyzed for convective rainfall events from 2012 to 2014 that triggered 998 debris flows in the western Sichuan basin (Eastern Tibet plateau). Three steps preprocess of beam blockage correction, vertical profile reflectivity correction and, and rain gage based bias correction are carried out. Four radar rainfall estimates by incrementally increasing accuracy from the above methods are used for the estimation of rainfall intensity–duration thresholds. The influence of rainfall accuracy on the estimation of the intensity–duration thresholds is analyzed. The sensitivity of the radar-based threshold to spatial location of rainfall and debris flows is analyzed and compared with rain gauge based thresholds. Finally, the benefits of intensity–duration thresholds derived from weather radar observations are demonstrated, especially for the case of short duration convective storms.