Remote sensing interpretation of debris flow material sources and its distribution characteristics in Miancu gully after Wenchuan earthquake

The Wenchuan earthquake has caused numerous landslides and avalanches as the sources for debris flows. A typical example is the Miancu Gully in Maoxian, where accumulates tremendous volume of loose solid materials that have formed 12 dammed lakes. Combining field surveys, Quickbird images (with spatial resolution of 0.61m) after the earthquake are used to identify the avalanches and landslides. Results show that there are 65 landslides and avalanches in the gully, amounting to area of 3.8×10⁶m². Among them there are 7 having area over 10⁶m². The 12 dammed lakes have a total area of 9.27×10³ m². The materials come mainly from the granite in the middle and the lower reaches, in volume of 1.56×10⁷m³, and those from the upper reaches are shallow landslides, in volume of 1.87×10⁶m³. Combining with metrological and loose materials sources conditions, tendency of debris flow activity is analyzed and some advices are proposed for Miancu gully debris flow countermeasure.