INTEGRATED ASSESSMENT AND ANALYSIS OF PHYSICAL LANDSCAPE PROCESSES THAT IMPACT THE QUALITY AND MANAGEMENT OF AGRICULTURAL WATERSHEDS
Location: Watershed Physical Processes Research Unit
Title: Rill development, headcut migration, and sediment efflux from an evolving experimental landscape
Submitted to: Federal Interagency Sedimentation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 29, 2010
Publication Date: June 27, 2010
Citation: Gordon, L.M., Bennett, S.J., Wells, R.R. 2010. Rill development, headcut migration, and sediment efflux from an evolving experimental landscape. In: Proceedings of the 9th Federal Interagency Sedimentation Conference, June 27-July 1, 2010, Las Vegas, NV. CDROM.
Interpretive Summary: Experiments were conducted to examine the processes of soil erosion and rill network development in the presence of simulated rain and changes in the downstream baselevel control. Rill incision, channel development, and sediment efflux occurred episodically in time, related directly to the imposed baselevel adjustments. While these rapidly-migrating headcuts caused rill incision and spikes in sediment efflux, the secondary waves of degradation driven by the minor headcuts were not expressed in the sediment discharge time series. Sediment efflux and drainage density approached nearly constant or asymptotic values for most the experiments, despite the continuous application of high-intensity rainfall. Thus sediment efflux and rill network development achieved steady-state erosion conditions similar to the declining equilibrium landscape when the system was not perturbed by the downstream baselevel control.
Experiments were conducted using a soil-mantled flume subjected to simulated rain and downstream baselevel lowering to quantify the growth, development, and evolution of rills and rill networks. Digital elevation models constructed using photogrammetric techniques greatly facilitated data acquisition and analysis. Results show that: (1) headcuts formed by baselevel lowering were the primary drivers of rill incision and network development, and the communication of this wave of degradation occurred very quickly and efficiently through the landscape, (2) rill networks extended upstream by headcut erosion, where channels bifurcated and filled the available space, (3) rill incision, channel development, and peaks in sediment efflux occurred episodically, linked directly to the downstream baselevel adjustments, and (4) sediment discharge and rill drainage density approached nearly constant or asymptotic values with time following baselevel adjustments despite the continuous application of rainfall. These findings have important implications for the prediction of soil loss, rill network development, and landscape evolution where headcut erosion can occur.