Evaluation of sediment load reduction by natural riparian vegetation in the Goodwin Creek Watershed

Authors: MOMM, HENRIQUE - Middle Tennessee State University; Witthaus, Lindsey; Bingner, Ronald - Ron; Wells, Robert - Rob; Kuhnle, Roger

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2019
Publication Date: 10/22/2019
Citation: Momm, H.G., Yasarer, L.M., Bingner, R.L., Wells, R.R., Kuhnle, R.A., Miranda, J. 2019. Evaluation of sediment load reduction by natural riparian vegetation in the Goodwin Creek Watershed. Transactions of the ASABE. 62(5): 1325-1342. https://doi.org/10.13031/trans.13492.
DOI: https://doi.org/10.13031/trans.13492

Interpretive Summary: Conservation planners require tools to better characterize agricultural landscapes and to estimate the effects of conservation practices at both the field and watershed scale. While these tools are often utilized to assess potential new practices, they can also be used to determine the effectiveness of current practices that are already in place. In Goodwin Creek watershed in Mississippi, natural riparian buffers are common features of the landscape and should be considered in modeling efforts. In this study, a geographic information systems (GIS) tool called AGBUF was utilized to characterize and evaluate the impact of natural riparian vegetation on sediment loads in Goodwin Creek watershed. AGBUF was used to simulate natural buffers, as well as scenarios of several different buffer widths. AGBUF estimated trapping efficiency by considering concentrated flow paths through the buffers that would lower their effectiveness. Through combining AGBUF with a watershed model, AnnAGNPS, more accurate simulations of sediment yield were achieved. These results provide evidence that AGBUF accurately estimates the influence of natural riparian buffers and can be used to more correctly simulate watersheds with natural as well as managed buffers.

Technical Abstract: In this study, the impact of natural and constructed riparian vegetation in reducing sediment loads was quantified at field and watershed scales in the Goodwin Creek experimental watershed in northern Mississippi, with the model Annualized Agriculture Non-Point Source-AnnAGNPS watershed pollutant model. Detailed characterization of actual natural riparian vegetation was performed by AGBUF GIS tools and integrated with the AnnAGNPS watershed pollutant model to estimate sediment loads. The specific objectives were focused on the model parametrization, the evaluation of the effect of concentrated flow paths (CFPs) to sediment yield and loads, and the comparison of sediment loads of different particle sizes under contrasting alternative scenarios with varying buffer width and concentrated flow paths assumptions. Simulation results indicate the potential of natural riparian vegetation to reduce up to 38%, 62%, and 70% of sediment yield for clay, silt, and sand particle sizes respectively when no concentrated flow paths (CFPs) through the riparian buffers are considered. Evaluations of simulations depicting actual conditions and with increasing assumptions of CFPs yielded higher agreement with observed sediment loads but with reduced gains in sediment trapping efficiency. At field scale, the flow network pattern influenced TE more when CFPs were varied than buffer widths. Simulation results denote the importance of maintenance to prevent CFPs, as comparisons of simulation containing constructed buffers alternatives suggest that narrower well-maintained buffers can be as efficient as wider buffers containing CFPs; but with the potential of removing less land from production.