CONTROLS ON BEDROCK SINUOSITY IN EASTERN TIBET

Eastern Tibetan Plateau bedrock rivers, including the Tsang Po, Irrawaddy, Salween, Mekong, and Yangtze, have sinuosities between 1.28 and 1.55m/m. Sinuosities between 25°N to 30°N, hand mapped in Google Earth, marginally decrease from west to east. This decrease in sinuosity parallels a regional gradient in tectonic activity across a region of constant rainfall and mean local relief. Although bedrock rivers in mountainous regions are generally assumed to have low sinuosities, studies of bedrock river sinuosity in Taiwan and Japan find that sinuosity post-dates channel incision. These studies argue that landsliding at the outside of meander bends is the primary driver increasing sinuosity in bedrock rivers. They find that sinuosity correlates with a gradient in monsoon rainfall: more rainfall leads to more landsliding, which in turn increases sinuosity. However, tectonic activity also increases landsliding; both Taiwan and Japan are tectonically active, thus, it is also possible that bedrock river sinuosity is controlled by tectonic activity. The tectonic gradient on the Eastern Tibetan plateau makes it an ideal study area to test this hypothesis. Preliminary results from our study area suggest that tectonic activity may be a greater control on bedrock river sinuosity than rainfall. Ongoing work includes investigating correlations between rainfall, erosions rates, tectonics, and sinuosity.