Abstract
Mass movements in mountainous areas are capable of damming rivers and can have a lasting effect on the river longitudinal profile. The long profile is commonly used to retrieve regional tectonic information, but how much dams may compromise geomorphometry-based tectonic analysis has not been systematically researched. In this study, we investigate the relationship between river dams and the longitudinal profile of the upper Indus River basin, based on interpretation and analysis of remote sensing imagery and digital elevation models (DEMs) and local field work. We identified 178 landslide, glacier and debris flow dams. Using TopoToolbox, we automatically extracted the river longitudinal profile from the 30 m SRTM DEM, determined the location of convex knickpoints and calculated the channel steepness index. One hundred and two knickpoints were detected with heights above 148 m, of which 55 were related to dams. There is good spatial correspondence between dams, convexities in the river longitudinal profile and relatively high steepness index. Different dam types have different impacts on the river profile; on the upper Indus, debris flow dams have a greater impact than landslide and glacier dams and can form knickpoints of up to 900 m. Therefore, dams may have a significant influence on the river longitudinal profile, knickpoints and steepness index, and should be considered when extracting information on regional tectonics using these indices.
Highlights
Rivers are a significant driving force of geomorphic evolution, and an important geomorphic unit that can record other driving forces such as tectonic activity and climate change (Whipple, 2000; Beaumont et al, 2001; Kirby and Whipple, 2001; Kirby et al, 2003; Whipple, 2004; Zhang et al, 2017)
We identify different types of dams in the upper Indus River basin and quantify their influence on the river longitudinal profile and knickpoint magnitude, in order to understand the geomorphic response of river damming
The distribution of the steepness index ksn seems to be influenced by topography and faults, with low values in the interior of the plateau and larger values at the edge of the plateau
Summary
Rivers are a significant driving force of geomorphic evolution, and an important geomorphic unit that can record other driving forces such as tectonic activity and climate change (Whipple, 2000; Beaumont et al, 2001; Kirby and Whipple, 2001; Kirby et al, 2003; Whipple, 2004; Zhang et al, 2017). The development of high-resolution and global digital elevation applications has facilitated extraction and analysis of the river longitudinal profile and they have been widely used to derive indexes of long-term tectonic evolution (Hu et al, 2010; Pánek et al, 2010; Goren et al, 2014; Willett et al, 2014; Yang et al, 2015; Wang et al, 2017). River longitudinal profiles and metrics derived from them, such as channel steepness indexes and knickpoints (Wobus et al, 2006), have become critical tools for studying the topographic evolution of mountain belts and deciphering changes in climate and tectonics (Bishop et al, 2005). As the number and spatial distribution of knickpoints and knickzones play an important role in interpreting tectonically active landscapes, it is critical that studies use a reproducible method of quantifying their locations (Gailleton et al, 2019)
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