ABSTRACT

This article summarizes an investigation into the likely role of landsliding in the formation of knickpoints along the Indus River in northern Pakistan. The knickpoints and their related geomorphic parameters (channel profile, concavity, drainage area, steepness index, etc.) were extracted from ASTER digital elevation models (DEMs) with 30 m resolution using ArcGIS and Matlab software. In total, 251 knickpoints were extracted from the longitudinal profile of the Indus River along an ~750-km-long reach upstream of Tarbela Dam. The identified knickpoint locations, along with their respective normalized steepness index (ksn values), were compared with the lithologic contacts, mapped faults, a regional-level landslide inventory, and the locations of prehistoric rockslides. The knickpoints identified adjacent to the prehistoric landslide dams (e.g., Katzarah, Gol-Ghone, and Lichar Gah, etc.) exhibited normalized steepness index (ksn) in the range of 500–1800 m0.9 at various locations along the river channel. The highest normalized ksn values (>1800 m0.9) were observed in the tectonically active Nanga Parbat Haramosh Massif region, where the river flows through narrow gorges, and/or where active thrust faults cross the river channel. This study reveals that the landslide dams appear to be one of the significant trigger factors in the formation of knickpoints along the Indus River.

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