LANDFORM DEGRADATION IN HIGH RESOLUTION: USING TERRESTRIAL LIDAR TO MEASURE EROSION RATES OF MORAINES IN THE EASTERN SIERRA NEVADA MOUNTAINS

Degradation is a fundamental process in the topographic change of a landscape. The spatial and temporal resolution of a landscape evolution model determines how accurately sediment transport over time reflects topographic changes on a landform. Moraines are landforms that record discrete histories of glacial activity by recording the location and direction a glacier once travelled. Hence they are excellent targets for studying landscape evolution and are continuous records of hillslope degradation processes – processes that transport sediment along landform surfaces. Such a record provides a source for measuring the sediment transported on multiple temporal and spatial scales.

On short time scales – from years to 100’s of years – there is a gap in data on sediment transport rates. It is this time scale which is critical for understanding landscape changes relevant to human beings. The current state of knowledge is problematic because the majority of current data is based on much larger temporal and spatial scales that do not provide a useful reference for landscape change that affects and is affected by human beings. On long time scales of 100,000’s to millions of years, catastrophic events are averaged out, and topographic change in a landscape evolution model appears gradual and incremental. On large spatial scales of kilometers, millimeter to centimeter scale sediment transport is unrepresented even though it is more frequent. High resolution temporal and spatial data of sediment transport is needed to accurately model landscape change at the landform scale.

In the current study, terrestrial LiDAR scans were taken a year apart along hillslopes formed by Quaternary moraines on the eastern front of the Sierra Nevada Mountains. Three-dimensional topographic change of moraine regolith - loose unconsolidated sediment - on these landforms was quantified at the millimeter to centimeter scale. The volumes and transport patterns of sediment change over a year were determined in order to calculate erosion rates on varying slope angles. Future work will use these rates to model hillslope evolution and diffusion processes in this region.