Riparian Land-Use Impacts on Stream Bank and Gully Erosion in Agricultural Watersheds: What We Have Learned

Abstract

Stream bank and gully erosion are major sources of nonpoint source pollutants, especially in landscapes dominated by agriculture. Implementation of upland conservation practices in landscapes dominated by agriculture reduces upland sediment transport more than water runoff, leading to excessive stream bank and gully erosion. This review focus on ten different studies conducted in streams in Iowa that investigated riparian land-use impacts on stream banks, gullies, and other riparian sediment sources (cattle loafing areas and cattle stream access points). The riparian land-uses investigated were riparian forest buffers; grass filters; continuous, rotational, and intensive rotational pastures; pastures with cattle fenced out of the stream; and row-cropped fields. Results of these studies indicate that maintaining perennial deep-rooted vegetation in riparian areas and excluding cattle from the stream channel stabilizes stream banks and gullies. Cattle loafing areas and cattle stream access points appear to also be important sediment sources. Re-establishing perennial riparian vegetation is a sustainable and cost-effective conservation practice because it reduces sediment in streams while maintaining the majority of the watershed in agricultural production. The limited available funds for the implementation of holistic watershed conservation practices suggest using targeted approaches, at the watershed scale, to improve conservation practice effectiveness.

Riparian Land-Use, Stream Morphology and Streambank Erosion within Grazed Pastures in Southern Iowa, USA: A Catchment-Wide Perspective

“…Studies have pointed out that well-justified decisions regarding stream water quality and morphology can only be made if multi-scale processes (plot, field, and watershed) are accounted for in an integrated way [9,13,15,27]. In our companion study, carried out in same pasture sites as this one, we found that stocking rates of the grazing sites were significantly correlated to measured field…”

“…at the watershed scale and, in some cases, it may mask improvement in sediment reduction achieved by the edge of field practices [10]. Along with the effects of stream geomorphologic adjustment, riparian land-uses such as row-crop and grazed pasture have been shown to increase the bank soil loss and associated total-P by destabilizing the bank soil and by altering the flow regime of the stream itself [15,27,31].…”

“…The larger catchment size or longer stream length translate into higher stage and stream power, which exerts greater stress on streambanks during high flow events [9]. This implies that when assessing streambank erosion at the field scale, it is important to account for the complexity of the entire stream channel network and its adjacent land-use introduced by scale differences [15]. Additionally, the gravitational force increases with bank soil saturation on the taller banks of higher order streams, which increases the soil bulk per unit weight [35], triggering bank failure and slumping.…”

“…In a riparian grazing system, the improvement in stream water quality will most likely be achieved with a set of integrated best management practices (BMPs) that are linked with stream geomorphic and hydrologic characteristics [15]. Additional resistance to stream flow can be introduced with a continuous cover of ground vegetation on the streambanks.…”

Permanent preservation areas in Mantiqueira sierra: perspectives for regularization along watercourses

“…The drainage network margins play an important role in water-resource conservation by acting on slope stabilization, channel maintenance, sediment containment, siltation prevention, and soil permeability maintenance (Zaimes et al, 2019). In order to ensure these functions, the Brazilian government established through the Native Vegetation Protection Law (Law n. 12,651/2012) minimum ranges that should be kept as "Permanent Preservation Areas" (PPAs).…”