Spatial Characterization of Riparian Buffer Effects on Sediment Loads from Watershed Systems

Abstract

Understanding all watershed systems and their interactions is a complex, but critical, undertaking when developing practices designed to reduce topsoil loss and chemical/nutrient transport from agricultural fields. The presence of riparian buffer vegetation in agricultural landscapes can modify the characteristics of overland flow, promoting sediment deposition and nutrient filtering. Watershed simulation tools, such as the USDA-Annualized Agricultural Non-Point Source (AnnAGNPS) pollution model, typically require detailed information for each riparian buffer zone throughout the watershed describing the location, width, vegetation type, topography, and possible presence of concentrated flow paths through the riparian buffer zone. Research was conducted to develop GIS-based technology designed to spatially characterize riparian buffers and to estimate buffer efficiency in reducing sediment loads in a semiautomated fashion at watershed scale. The methodology combines modeling technology at different scales, at individual concentrated flow paths passing through the riparian zone, and at watershed scales. At the concentrated flow path scale, vegetative filter strip models are applied to estimate the sediment-trapping efficiency for each individual flow path, which are aggregated based on the watershed subdivision and used in the determination of the overall impact of the riparian vegetation at the watershed scale. This GIS-based technology is combined with AnnAGNPS to demonstrate the effect of riparian vegetation on sediment loadings from sheet and rill and ephemeral gully sources. The effects of variability in basic input parameters used to characterize riparian buffers, onto generated outputs at field scale (sediment trapping efficiency) and at watershed scale (sediment loadings from different sources) were evaluated and quantified. The AnnAGNPS riparian buffer component represents an important step in understanding and accounting for the effect of riparian vegetation, existing and/or managed, in reducing sediment loads at the watershed scale.

Assessing impacts of riparian buffer zones on sediment and nutrient loadings into streams at watershed scale using an integrated REMM-SWAT model

“…The Riparian Ecosystem Management Model (REMM) is a process based model that has been used to simulate the effect of riparian buffers on reducing sediment, nitrogen (N), and phosphorus (P) at field scale (Liu, Yang, & Wang, ; Lowrance et al, ). Also, an important model supported by the United States Department of Agriculture is the Annualized Agricultural Nonpoint Source (AnnAGNPS) Pollution Model which has been used to evaluate the long‐term effect of agricultural farming and conservation practices on nonpoint source pollutants (Momm, Bingner, Yuan, Locke, & Wells, ). It predicts the origin and movement of water, sediment, and chemicals at any location in the watershed.…”

Characterization and Placement of Wetlands for Integrated Conservation Practice Planning

“…Any standard GIS-based software package with topographic capability could be used; however, the existing integration between wetland components and other AnnAGNPS components simplifies the input preparation. TOPAGNPS is a subset of the topographic parameterization (TOPAZ) program (Garbrecht and Martz, 1996) with incorporation of enhanced components to link spatial characterizations of ephemeral gullies and riparian buffers (Momm et al, 2012(Momm et al, , 2014. TOPAGNPS uses digital elevation models (DEMs) in raster grid format to preprocess, identify, and measure topographic features, define the spatial extent of surface drainage, and depict the channel network pattern to support watershed hydrologic modeling and analysis.…”

“…The main capabilities of AgWet include: (1) automated watershed-scale characterization of individual wetlands, (2) automated generation of the AnnAGNPS wetland input database, (3) iterative assistance for watershed-scale determination of potential sites for new wetland implementation, and (4) user-defined criteria for filtering potential sites. Combining AgWet with other existing components within AnnAGNPS provides the means for spatiotemporal analysis of different types of sediment and agrochemical sources, farming practices, and conservation alternatives (Momm et al, 2012(Momm et al, , 2014.…”

Delineating and mapping riparian areas for ecosystem service assessment

“…Numerous approaches to delineate riparian areas have been undertaken ranging from simplistic models in which a fixed‐width buffer is implemented (Hawes & Smith, ; Stoffyn‐Egli & Duinker, ), to more complex holistic approaches where the most relevant riparian characteristics such as soil properties, associated floodplain extent, vegetation type, or hydrologic parameters are integrated into delineation models of varying complexity. These are subsequently used to generate a variable‐width riparian buffer (Abood & Maclean, ; Baker, Lawrence, Montagne, & Patten, ; Belletti et al, ; Lyons, Görres, & Amador, ; Momm & Bingner, ). However, recent approaches are more inclined to disregard fixed‐width buffers as they can be grossly inaccurate due to the poor and inconsistent relationship between riparian width and its ecological functionality (Abood & Maclean, ; Abood, Maclean, & Mason, ; Aunan, Palik, & Verry, ).…”

“…hydrologic parameters are integrated into delineation models of varying complexity. These are subsequently used to generate a variablewidth riparian buffer (Abood & Maclean, 2011;Baker, Lawrence, Montagne, & Patten, 2006;Belletti et al, 2017;Lyons, Görres, & Amador, 1998;Momm & Bingner, 2014). However, recent approaches are more inclined to disregard fixed-width buffers as they can be grossly inaccurate due to the poor and inconsistent relationship between riparian width and its ecological functionality (Abood & Maclean, 2011;Abood, Maclean, & Mason, 2012;Aunan, Palik, & Verry, 2005).…”