Assessing Sediment Fluxes Within Evolving Rill Networks in an Experimental Landscape
Abstract
In an effort to better understand the spatial and temporal variation in sediment fluxes within actively evolving rill drainage networks, high-resolution, photogrammetrically-derived ortho-rectified photographs and digital elevation models of an experimental landscape were analyzed and compared to basin-outlet sediment signatures. Within a large 7.1 x 2.4 M flume, a sandy-loam soil bed was prepared at a 5% slope with a broad central concavity, to represent a natural drainage basin. This soil bed was subjected to repeated simulated rainstorms of known intensity. During these storms, rill erosion was initiated by a period of intense headcut development and migration and very high sediment yield in response to baselevel lowering at the flume outlet. After this initial period of adjustment, a number of sequential waves of degradation propagated throughout the rill network, scouring pre-existing channels and extending the upstream extent of network tributaries. These bursts of activity were often interspersed by periods of relative quiescence. While these secondary waves were clearly visible and quite pronounced with regard to their effect on rill network morphology, they appeared to have little effect on basin-outlet sediment signatures. Rill networks quickly attained a steady-state sediment yield at the basin outlet regardless of changes in internal drainage network morphology and sediment fluxes. Only in the presence of a secondary drop in baselevel was the equilibrium of the steady state rill network upset - to systematically adjust once again and attain another steady-state condition. These data provide a unique opportunity to examine the initiation and exploitation of landscapes by rill erosion under controlled conditions employing extremely precise datasets with a very high temporal and spatial resolution. These findings have important implications for understanding the relative magnitude of internal and external controls on drainage network development and landscape evolution.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2009
- Bibcode:
- 2009AGUSM.H74B..03G
- Keywords:
-
- 1815 Erosion;
- 1819 Geographic Information Systems (GIS);
- 1825 Geomorphology: fluvial (1625);
- 1848 Monitoring networks;
- 1872 Time series analysis (3270;
- 4277;
- 4475)