Grain Size Distribution Dictates the Effect of Climate on Hillslope Erosion
Abstract
It is generally accepted that for any given slope, increases in rainfall rate will increase erosion. It follows then that changes in climate should coincide with changes in erosion rate. We used a variety of field methods and terrestrial LiDAR repeat scans of bare earth surfaces on moraines in eastern Sierra Nevada, California, USA. We calculated annual erosion and sediment transport during 2010-2011, and they were found to vary among the moraines. Given similar morphologies, slopes, and vegetation patterns within the same climatic region, sediment mobility patterns exhibited in the terrestrial laser scans also showed wide variations.
While grain size distribution for glacial till is expected to vary considerably, the results for sediment transport and mobility on the moraine surfaces gave rise to questions relevant for hillslope erosion study in landscapes in all climates. It also provided opportunity to study mixed granular flow in a natural environment and address two fundamental questions. How does grain size distribution effect sediment transport rates and subsequent hillslope degradation? How does grain size distribution mediate the effects of climate change on erosion and hillslope stability? Results collected from the present study address these questions through analyses of terrestrial laser scan difference surfaces together with field measures of erosion rates from sediment traps and sediment transport from pebble lines and repeat photo assessment. Grain size distributions coincided with variations in erosion rates and transport on different moraines in the region at the landform scale. This suggests that grain size distribution can mediate the effects of climate on hillslope erosion rates. Considering that hillslope diffusion modeling for the Mono Basin moraine in the study region showed small variation in erosion rates through 85 ka, even with a time-varying climate parameter, the results imply that grain size distribution dictated the effects of climate change on hillslope erosion in this region.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMEP52B..07M
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 1630 Impacts of global change;
- GLOBAL CHANGEDE: 1807 Climate impacts;
- HYDROLOGYDE: 1824 Geomorphology: general;
- HYDROLOGY