Formation Condition, Disaster Characteristics and Developing Trend Analysis on Debris Flows in Moxi River Basin, SW China

Abstract

Moxi river basin is located on the east piedmont of Mt. Gongga. Based on field investigation, 49 typical debris flows which could threat local residents and important equipments directly have been identified. In this paper, formation condition, initiation mechanism, typical characteristics and developing trend were analyzed, and countermeasures were put forward. Conclusions were drawn as follows: (1) It is the special geo-environment background made the solid materials very loose and abundant. More than 3 × 107 m3 loose solid materials are prone to be supplied to debris flow by means of collapse, landslides, erosion and entrainment. (2) Debris flows were principally triggered by the intense intraday rainfall and antecedent effective rainfall accumulating for 6 days before debris flows occurred. Their quantitative equation was established with a power-law relation and can be employed as disaster warning line. (3) Debris flows in Moxi river basin usually occur in group quasi-periodically and present chain effect. (4) Up to 43 gullies are differentiated at stages of their formation and developing. Combined with influence of climate trend, the occurrence probability of debris flows will still be high in this drainage in future. (5) As Moxi river basin is a famous scenic spot, prevention of debris flow should be given priority there and combined with the tourism planning. It is of great importance to protect Moxi platform through avoiding lateral erosion and collapse.