Lithologic and tectonic controls on bedrock channel form at the northwest Himalayan front

Abstract

[1] Recognition that channel form reflects a river's ability to erode rock and transport material has spawned stream-power models that estimate incision patterns by approximating energy dissipation within a channel. These models frequently assume that channel width scales as a power law with drainage area, partly because drainage area is easily extracted from digital elevation models (DEMs). However, this assumption is often confounded by local variations in rock strength and rock-uplift rate that can cause channel constriction downstream. Here we investigate the morphological response to spatial changes in rock strength and rock-uplift rate of 10 bedrock channels traversing the Mohand range along the northwest Himalayan front. We present a new method to continuously measure and compare channel width, slope, and other hydraulic parameters that integrate satellite imagery and DEM analysis. Our method corrects for an~13% overestimation of average channel gradient from a 90 m resolution DEM that arises from short circuits of fine-scale meanders. We find that channels (1) narrow >1 km upstream from knickpoints formed by an increase in rock strength, (2) adjust laterally more than vertically in response to downstream decreases rock erodibility and uplift rate, and (3) meander where shear stresses are high and channel widths are low. We attribute these results to a high ratio of sediment supply to transport capacity, which enhances lateral erosion relative to vertical incision. Our results suggest that substrate strength and sediment supply substantially influence channel form and that channel width should be explicitly measured when interpreting tectonic signals from bedrock channel morphology.Citation: Allen, G. H., J. B. Barnes, T. M. Pavelsky, and E. Kirby (2013), Lithologic and tectonic controls on bedrock channel form at the northwest Himalayan front,

Quantifying river form variations in the Mississippi Basin using remotely sensed imagery

“…As the DHG parameter most readily observable from remotely sensed data, river width has been quantified using a variety of passive and active sensors since the early stages of the Landsat satellite program in the 1970s (Rango and Salomonson, 1974;Watson, 1991;Smith et al, 1996, Allen et al, 2013. While remote sensing of channel width has generally covered single rivers or limited spatial extents, recognition of the potential for large-scale width measurement has recently led to regional and global studies Yamazaki et al, 2014;Andreadis et al, 2013).…”

“…Its functionality allows calculation of river width at each pixel in an automatically derived river centerline, and it can be used on both single-channel and multichannel river reaches. Previous studies have used inputs from MODIS (Moderate-Resolution Imaging Spectroradiometer), Landsat, SPOT-5 (Satellite Pour l'Observation de la Terre) images, and the U.S. Geological Survey's NLCD Allen et al, 2013;Pavelsky et al, 2014). In this study, we used the open-water class in the NLCD as input to calculate river widths for the Mississippi Basin.…”

“…To build DHG relationships continuously downstream, we used upstream drainage area as a proxy for discharge. We calculated drainage area from the 90 m resolution HydroSHEDS (Hydrological data and maps based on SHuttle Elevation Derivatives at multiple Scales) digital elevation model (DEM) (Lehner et al, 2008) and then assigned the nearest drainage area value to each RivWidth pixel using the methodology developed by Allen et al (2013) (Fig. 3).…”

Bedrock channels response to differential rock uplift in eastern Qilian Mountain along the northeastern margin of the Tibetan Plateau

“…Therefore, bedrock channel longitudinal profiles have been regarded as more sensitive indicators of uplift rates than other morphological properties in active orogen (Whipple, 2004). The spatial distribution of rock uplift and substrate active faults can be determined directly by analyzing the systematic behavior of stream profiles in tectonically active region (e.g., Allen et al, 2013;Hack, 1957Hack, , 1973Kirby et al, 2007Kirby et al, , 2003; Kirby and Ouimet, 2011;Kirby and Whipple, 2001;Lavé and Avouac, 2001;Oskin et al, 2014;Pritchard et al, 2009;Wobus et al, 2003;Yanites et al, 2010).…”

Possible threshold controls on sediment grain properties of Peruvian coastal river basins

“…The size and shape of gravels bear crucial information about (i) the transport dynamics of mountain rivers (Hjulström, 1935;Shields, 1936;Blissenbach, 1952;Koiter et al, 2013;Duller et al, 2012;Attal et al, 2015), (ii) the mechanisms of sediment supply and provenance (Parker, 1991;Paola et al, 1992a, b;Attal and Lavé, 2006), and (iii) environmental conditions such as uplift and precipitation (Heller and Paola, 1992;Robinson and Slingerland, 1998;Foreman et al, 2012;Allen et al, 2013;Foreman, 2014). The mechanisms by which grain size and shape change from source to sink have often been studied with flume experiments (e.g.…”