Ephemeral gully channel width and erosion simulation technology

Abstract

Concentrated surface runoff, such as associated with ephemeral gully channels, increases erosion and transfers fine sediment and associated agrichemicals from upland areas to stream channels. Ephemeral gully erosion on cropland may contribute up to 40 % or more of the sediment delivered to the edge of agricultural fields, significantly threatening the health of downstream ecological services. Typically, conservation practices developed for sheet and rill erosion are also expected to treat ephemeral gully erosion, but technology and tools are needed to account for the separate benefits and effects of practices on various sediment sources. Without improved research studies, subjective observations will continue to be used to satisfy quality criteria in lieu of scientifically defensible, quantitative methods to estimate the impact of gully erosion. Ephemeral gully channels evolve by one, or combination of, complex physical process in the form of incision, headcut migration upslope, and channel sidewalls expansion (widening). This study focused on the latter, ephemeral gully channel widening relationships. The impact of various width functions on erosion can be very significant and is dependent on discharge, slope, soil properties, and management conditions. A description

Modelling Ephemeral Gully Erosion from Unpaved Urban Roads: Equifinality and Implications for Scenario Analysis

“…The gully width was calculated within AnnAGNPS using the Wells’ Equation [ 45 ], which was developed in experimental conditions using packed soil beds under similar soil textures as those observed in SB, expressed as: where W is the gully width (m); Q p the peak discharge at the gully head (m 3 /s); and S is the average bed slope above the gully head (m/m). Other relationships were investigated for use by AnnAGNPS [ 46 ], with the Wells approach providing the best response for gullies that are repaired. Many other empirical relationships have been developed for gullies or channels that were not repaired, but in the watershed for this study, gullies are repaired after precipitation events, and therefore encouraged us to use it for this analysis.…”

Gully erosion processes, disciplinary fragmentation, and technological innovation

“…decimeters), and the erodibility of the soil due to turbulent shear. Subsequent revisions included an actively migrating headcut at the gully head, erosion, transport, and deposition of sediment mixtures, various gully width predictors, and different management scenarios (Gordon et al, , ; Bingner et al, ). Dabney et al .…”

“…This model was conceptualized as a large, single channel occupying a topographic swale whose channel dimensions were a function of overland flow (most notably peak discharge), the depth of the tilled soil (c. decimeters), and the erodibility of the soil due to turbulent shear. Subsequent revisions included an actively migrating headcut at the gully head, erosion, transport, and deposition of sediment mixtures, various gully width predictors, and different management scenarios (Gordon et al, 2007(Gordon et al, , 2008Bingner et al, 2016). Dabney et al (2015) adopted a similar approach to include ephemeral gully erosion in the spatiallydistributed RUSLE2 model.…”

Physically based model for gully simulation: application to the Brazilian semiarid region

“…The Foster and Lane model (FLM), as proposed by its authors, considers a single source of erosion: the soil detached from the channels bed and walls due to shear stress. Field observation and the literature (Blong and Veness, 1982), however, show that wall instability and failure can represent a significant source of sediment. To estimate the effect of wall erosion at the study site, we proposed an empirical parameter (λ -Eq.…”