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Orogenic landscapes around the world have undergone spatio-temporal variations due to changes in tectonics and climate. Disentangling the influence of these drivers on the topography remains a challenge due to the complex feedbacks that exist between them. Research has shown that bedrock rivers adjust their morphology in response to the variations in landscape, making morphological parameters useful for constraining tectonic uplift over the 103-105 year timescale. However, rivers are significantly affected by sediments as the impact-based erosion of bedrock varies depending on the extent of bedrock exposure and sediment cover, potentially obscuring the tectonic signature encoded in river systems. Therefore, to accurately delineate the tectonic signal from the landscape, we must account for the effects of sediment transport on the river morphology that is currently missing in the commonly used stream power models.
Taiwan provides a natural laboratory to address this problem due to its high seismicity, pronounced exhumation rate gradients and relatively uniform long-term precipitation. Morphological parameters like channel steepness do not scale with bedrock incision rates but show a more robust relationship with basin averaged 10Be erosion rates. We assess the influence of sediment dynamics by estimating the bedload transport capacity at 112 sample points in Taiwan across six major geological divisions. The required grain size, channel width & slope data were collected over two field seasons, and daily mean & peak flood discharge data were compiled from hydrological yearbooks. The absolute transport capacities for these rivers exhibit a strong correlation when compared to their corresponding 10Be erosion rates. These findings suggest that river evolution in tectonically active regions is shaped by their ability to transport sediment from upstream, particularly where local river morphology does not directly reflect tectonic uplift.
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