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ARS Home » Midwest Area » West Lafayette, Indiana » National Soil Erosion Research Laboratory » Research » Publications at this Location » Publication #253480

Title: Pore water effects on soil erodibility and its implication in ephemeral gully erosion modeling

item NOUWAKPO, SAYJRO - Purdue University
item Huang, Chi Hua

Submitted to: Joint Federal Interagency Sedimentation and Hydrologic Modeling
Publication Type: Proceedings
Publication Acceptance Date: 8/1/2009
Publication Date: 6/27/2010
Citation: Nouwakpo, S., Huang, C. 2010. Pore water effects on soil erodibility and its implication in ephemeral gully erosion modeling. Joint Federal Interagency Sedimentation and Hydrologic Modeling, June 27-July 1, 2010, Las Vegas, NV.

Interpretive Summary:

Technical Abstract: Ephemeral gully erosion is the main source of sediment from the agricultural landscape, unfortunately, it has been overlooked in traditional soil erosion assessment. Field observations, and subsequent support from controlled lab experiments, have shown the linkage between transient soil hydraulic condition and initiation of rills or incised channels, specifically when the soil was oversaturated and exfiltration or upward seepage occurred. In order to properly account for this hydraulic effect, we propose to modify the soil erodibility parameters to accommodate the transient soil moisture condition. We used a mini-flume and empirically measured rill erodibility and critical shear stress of a silt loam soil under free drainage, saturation and upward seepage conditions. The mini-flume results showed similar magnitudes of soil loss as compared to a prior study performed on a 5m long 1.2 m wide soil box which required a large amount of soil just to fill the box. We then used two separate approaches to quantify the hydraulic condition when sediment detachment was initiated. The first technique was to use the mini flume and observe the incipient sediment detachment as flow shear stress was increased. The second approach was based on the fluidized bed principle to calculate the head loss at fluidization or incipient failure. By comparing the fluidization velocity of the cohesive soil to that of an equally dense non-cohesive material, we calculated the inherent soil cohesion. This result led to the calculation of critical shear stress at different vertical hydraulic gradients. We plan to incorporate this erodibility adjustment with soil profile and topographic attributes in a hillslope hydrologic model to quantify ephemeral gully development.