期刊
JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE
卷 118, 期 3, 页码 1806-1825出版社
AMER GEOPHYSICAL UNION
DOI: 10.1002/jgrf.20113
关键词
Bedrock river channels; Hydrologic scaling; Fluvial geomorphology; Remote sensing; Siwalik Hills; Mohand
资金
- NSF [EAR 0814723]
- UNC Geological Sciences Martin Fund
- GSA Graduate Research Grant
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 similar to 13% overestimation of average channel gradient from a 90m resolution DEM that arises from short circuits of fine-scale meanders. We find that channels (1) narrow >1km 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.
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