Active Tectonics And Alluvial Rivers PDF Download

In environments characterised by active tectonics, it is widely accepted that river morphology will be affected by active fault displacement. For example, there is documented evidence of change in channel slope, channel width, channel braiding patterns, grain size distribution trends, and stream power in response to active faults. Therefore, river morphology can carry a measurable signature of tectonic activity. Furthermore, it can be hypothesised that fluvial systems are in fact more sensitive to local faulting than raw topographic expression. This would mean that young active faults will affect river morphology before they are expressed in the local topography. Therefore, detailed morphological measurements of rivers in tectonic settings could allow for an early detection of faulting which is not yet expressed in the landscape. The Dehradun region of the Northwest Himalayan foothills is an ideal test case for this hypothesis. In this area, the Ganges and Yamuna rivers flow across an active thrust fault system, which is not yet clearly visible in the landscape. Therefore, longitudinal river profiles of the Ganges and Yamuna rivers from the Lesser Himalaya mountain front to ~35 km into the Gangetic Plain were extracted from a 90 m Digital Elevation Model and hydraulic features, including width of channel belt, channel slope, and geomorphic characteristics, were collected from IRS 23.5 m satellite images. Stream power was calculated by using channel slope and monthly discharge data. These data were complemented by field measurements of bed material grain sizes at ~5 km intervals. All data were analysed for the ~80 km Ganges and Yamuna reaches flowing from the Main Boundary Thrust, through the alluvial Dehra Dun valley and across the suspected active Himalayan Frontal Thrust, and ~35 km out into the Indo-Gangetic foreland. The longitudinal profile, width of channel belt, channel slope, braiding relationship, pattern of stream power, and grain size distribution all ind.