Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2005
Publication Date: 9/21/2005
Citation: Bennett, S. J., Alonso, C.V. 2005. Kinematics of flow within headcut scour holes on hillslopes. Water Resources Research 41, W09418, doi: 10.1029/2004WR003752, 2005.
Interpretive Summary: The formation and upstream migration of headcuts in rills, row-crop furrows, and ephemeral gullies is an important factor in soil losses and sediment yield from agricultural lands. Improvements in soil erosion predictions are predicated upon better characterizations of these processes. Recent experimental research has added new insights on erosion due to headcuts migrating on homogeneous soil horizons. It was observed that the morphology of the headcut did not vary significantly during its migration once steady-state conditions were achieved. The present experiments were conducted using fixed headcut models patterned after live steady-state headcuts to define the turbulent flow structure within these erosional features and to assess the applicability of existing physically-based conceptualizations of headcut migration. The results confirm the applicability of algorithms incorporated in a headcut erosion model recently published by the authors. This work is relevant to ARS, other federal and state agencies, and to the US farming community because it allows us to make improved predictions of how much soil erosion will occur on agricultural lands.
Technical Abstract: The development and migration of headcuts in rills and gullies can adversely impact soil resources in agricultural areas and accelerate landscape degradation worldwide. Analytical treatments of this erosion process have been based on a turbulent impinging jet analogue, though partially validated by field and laboratory data. Experiments were conducted using fixed headcut models to define the turbulent flow structure within these erosional features and to assess the applicability of turbulent jet theory to characterize this flow domain. These data show that: (1) flow within headcut scour holes is analogous to plane turbulent reattached wall jets, and (2) similarity arguments used to define the limits, length scales, and velocity distributions in the free jet and wall jet regions of the flow field are applicable. This study contributes new knowledge on the hydrodynamic of flow processes within a headcut environment, confirms the applicability of jet theory for analyzing such processes.