Meeting:Abstract 2011 CSDMS meeting-087
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Predicting sediment yields from undisturbed catchments: the dominant role of tectonics
[[Image:|300px|right|link=File:]]A major issue, hampering our understanding about the human impacts on sediment fluxes is our limited knowledge about the magnitude and controlling factors of catchment sediment yields (SY, t km-2 y-1) under ‘baseline’ conditions, i.e. the SY that could be expected from a catchment if it was unaffected by human impacts. To address this problem, a dataset was set up with measured SY-data from 146 catchments in Europe that are little or not affected by humans in terms of land use and have no significant reservoirs, lakes, impoundments or glaciers in their upstream area. The considered catchments span a wide range in catchment areas (0.3 – 4,000km²) and observed SY-values (0.5 – 3,100 t km-2 y-1). Analyses of these data indicates that climate exerts little control on the observed range of SY-values. However, strong correlations were found between SY and average catchment slope, lithology and tectonic activity (as derived from a globally available earthquake hazard map). Based on these findings, a regression model was developed that allows predicting baseline SY. Model calibration and validation results indicate that this model is able to provide robust approximations of the baseline SY, with >95% of predictions deviating less than one order of magnitude from the measured SY-values. This model can therefore significantly improve our understanding about the controlling factors of SY and their sensitivity to human impacts. However, it is also the first model that explicitly considers the effect of tectonic activity on catchment SY. Despite the relatively limited tectonic activity in many of these catchments, differences in earthquake sensitivity alone was found to explain already more than 40% of the observed variation in SY. Our results therefore illustrate that tectonic activity has a strong, but hitherto largely neglected, influence on SY.