Geomorphic modeling of hillslope sediment size distribution Inyo Creek, eastern Sierra Nevada

Landscape evolution and climate are linked by river bed sediments, which regulate the efficiency of river incision into bedrock. The sediment delivered to a stream channel depends on the topography of the surrounding hillslopes, and climatic variables like temperature, precipitation, and vegetation. Yet there is little in the way of theory or data to predict how climate influences patterns in hillslope sediment size distributions at the watershed scale. To address this knowledge gap, we are investigating hillslope sediment production in the steep granitic catchment of Inyo Creek, in the eastern Sierra Nevada of California.We expect the geomorphic and climatic factors that influence temperature and water residence time, and thus the intensity of chemical versus mechanical weathering, will correlate with resulting hillslope sediment sizes. The resulting map analysis predicts that 50% of the catchment will be dominated by boulder-size sediment, with smaller sediments dominating lower elevations. Our prediction accuracy is significant and we find a strong positive correlation with elevation. Including slope and aspect with elevation predicts areas where larger clasts dominate even at lower elevations. These results illustrate how climate-controlled hillslope sediment production can influence river sediment supply, and thus bedrock incision and landscape evolution.