Complex spatial and size distributions of landslides in the Yarlung Tsangpo River (YTR) basin

The Yarlung Tsangpo River (YTR), located in the Himalayan orogenic belt, is renowned for its deep gorges and complex tectonic features, as well as its reputation as a landslide-prone region. However, less is known about the distribution of landslides across the entire river basin. To address this gap in knowledge, this study first established a comprehensive landslide inventory across the entire basin using remote sensing mapping and multiple field investigations. Then, a systematic analysis of the spatial and size distributions was conducted. The results indicated that the YTR basin features at least 2390 landslides with areas exceeding 104 m2, spanning a total area and volume of 1087.6 km2 and 48.4 km3, respectively. These landslides can be classified into eight types, and rockslides are the most common (53.1%). Their distributions are highly asymmetric, with the following notable patterns: (1) the Tsangpo suture zone (53.4%) contains a greater number of landslides than other tectonic units; (2) the landslide size is influenced by the relief and elevation conditions, with positive relationships observed between the local relief and landslide area, as well as between the elevation range and landslide area; and (3) the landslide distribution is not significantly correlated with rainfall, and seasonally frozen ground is associated with a greater concentration of landslides. Alternating slate and shale groups in the Tsangpo suture zone may be the factors responding to landslide concentration. A total of 20.6% of landslide-blocked rivers were observed, with some forming river knickpoints. Due to the limited data, spatial and size analyses are perhaps immature, and further systematic analysis remains necessary.