Disaster characteristics and optimal design of drainage canal of debris flow following wenchuan earthquake in weigou gully in beichuan county, sichuan province, china

Abstract

The Weigou Gully, a branch of Pingtong River, is located in Guixi Township, Beichuan County. The area was seriously affected by the Wenchuan earthquake and its aftermath. Debris flows occurred on September 24, 2008, July 14, 2009, and September 10, 2009, threatening the safety of the inhabitants and their property. Debris flows in Weigou Gully were mainly supplied by landslides triggered by the earthquake. The debris flows had characteristics of high frequency, high bulk density and coarse particle size. Following the earthquake, the frequency of debris flows increased. Based on the analysis of the disaster characteristics, the optimal cross-section design method for the “trapezoid-v” shaped debris flow drainage canal of the Weigou Gully is discussed. The depths (h1 and h2) of the cross-section of the “trapezoid-v” shaped drainage canal and the optimal cross-section parameters using these two measurements are defined. In addition, several formulas for calculating the cross-section measurements are deduced under optimal hydraulic conditions when discharge (Q), debris grain composition (D50 and D10) and longitudinal ratio (I) are known. Finally, the optimal dimensions for the cross-section of the Weigou Gully debris flow canal are determined.