Location: Watershed Physical Processes ResearchTitle: Ephemeral gully channel width and erosion simulation technology Author
|Bingner, Ronald - Ron|
|Wells, Robert - Rob|
|Momm, Henrique - Middle Tennessee State University|
|Rigby, James - Jr|
|Theurer, Fred - Retired Non Ars Employee|
Submitted to: Natural Hazards
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2015
Publication Date: 1/17/2016
Publication URL: http://handle.nal.usda.gov/10113/61815
Citation: Bingner, R.L., Wells, R.R., Momm, H., Rigby Jr, J.R., Theurer, F.D. 2016. Ephemeral gully channel width and erosion simulation technology. Natural Hazards. 80(3):1949-1966.
Interpretive Summary: Ephemeral gullies serve as effective links transferring sediment and associated agrichemicals from upland areas to stream channels. Technology has recently been developed that incorporates state-of-the-art ephemeral gully science within watershed models. This includes the scour that is produced below ephemeral gully headcuts and the rate that the headcuts move up into the agricultural fields after rainfall events. Through the application of tillage operations on a field, the land surface may be disturbed and ephemeral gullies filled in and repaired from previous erosion events. Ephemeral gully processes included within watershed models thus provides a tool that can determine the effect of conservation management practices and changing soil conditions on the development of ephemeral gully erosion. This study describes the impact of selecting various ephemeral gully widening functions within watershed models on erosion. The depth of tillage from management practices influences the results from various width functions, where some functions do not consider depth to a non-erodible. Additional research is needed to fully understand the processes that widen and erode ephemeral gully channels. When ephemeral gullies are present, land managers should acknowledge the implications of repairing ephemeral gullies during tillage operations and consider alternative conservation practices that reduce ephemeral gully erosion separately from those that control sheet and rill erosion, ensuring the long-term productivity of their land.
Technical Abstract: Concentrated runoff increases erosion and transfers fine sediment and associated agrichemicals from upland areas to stream channels. Ephemeral gully erosion on cropland in the U.S. may contribute up to 40% or more of the sediment delivered to the edge of the field. 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. Practices specifically developed to treat ephemeral gully erosion need further testing, when used in conjunction with sheet and rill erosion control practices. 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. Some of the more important limiting components are the identification of and relationships for: (1) selecting appropriate ephemeral gully width algorithms; (2) soil resistance to gully erosion including a definition for non-erosive layers; (3) the effect of root mass and above ground vegetation on erosion resistance; (4) the impact of ephemeral gully channel network formation on gully evolution; and (5) the effect of subsurface flow on ephemeral gullies. The impact of various width functions on erosion can be very significant and is dependent on discharge, slope, soil properties, and management conditions. Improvements in the development of ephemeral gully width algorithms are critical to understanding the impact of conservation practices on controlling ephemeral gully erosion. Tools are needed to predict and quantify ephemeral gully erosion, including the capability to evaluate the effect of conservation practices to control erosion. Conservation management planning by agencies within USDA and other organizations needs a systematic approach to determining the extent of ephemeral gully erosion problems on a field, watershed, or national basis, or to predict the recurring or new locations of ephemeral gullies prior to their development.