Classification and sediment estimation for debris flow-prone catchments in the Parlung Zangbo Basin on the southeastern Tibet

Abstract

Glaciers in alpine mountains create special landforms that store large amounts of sediment, providing loose materials for debris flows. Various types of catchments have diverse storage modes for such materials, resulting in differences in the location and volume of sediment. However, little is known about this phenomenon due to the lack of data. Hence, taking the Parlung Zangbo basin as an example, we identify the main sediment according to the catchment type and propose sediment calculation methods for different types. The results show that tributary catchments can be divided into five types: deep U-shaped catchments, shallow U-shaped catchments, glacial hanging catchments, fluvial catchments after glaciation, and fluvial catchments. The sediments include glacial deposits, landslides, talus slopes, fans, etc. Non-glacial sediments can be calculated by the morphological method, while the thickness of glacial deposits can be calculated effectively by the proposed curve-fitting method. The volumes of glacial deposits are obtained and compared with those of other sediments. Glacial deposits are one or two orders of magnitude larger than other deposits. Glacial deposits in the first three types are concentrated on gentle downstream slopes, while in the fourth type was in steep location.