Three decades of ephemeral gully erosion studies

Authors: LIU, GANG - Northwest A&f University; ZHENG, FENLI - Northwest A&f University; Wilson, Glenn; XU, XIMENG - Northwest A&f University; LIU, CHANG - Northwest A&f University

Submitted to: Surveys in Geophysics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2021
Publication Date: 5/6/2021
Citation: Liu, G., Zheng, F., Wilson, G.V., Xu, X., Liu, C. 2021. Three decades of ephemeral gully erosion studies. Surveys in Geophysics. 212:105046. https://doi.org/10.1016/j.still.2021.105046.
DOI: https://doi.org/10.1016/j.still.2021.105046

Interpretive Summary: Concern for ephemeral gully (EG) erosion has been growing among the research community which has prompted this state-of-the-science review to identify knowledge gaps. This study was based on an extensive search of published literature in the Web of Science database which identified 173 papers published in 56 scientific journals over the last 30 years on EG erosion. The main EG erosion topics were related to the gully erosion processes, factors, methodology, models, and effects. The concepts behind the definition of an EG was identical worldwide, however, there is a need to develop a consensus on the critical morphological values under different conditions for identifying EG channels in order to map and model their development quickly and accurately. Topographic factors have been much more studied than other impact factors, including climate, land management, soil, and hydraulics. The interactive effects of different factors impacting EG erosion across a variety of size areas and time frames should be further researched. Fifteen different methods or technologies were categorized into four kinds of methods, including soil monitoring, modelling, simulation experiments, and reviews, have been employed to assess and quantify EG erosion. The average soil erosion rate of EGs in 36 publications increased with an increase in slope gradient and decreased with the increase in catchment area. The number of EGs increased with catchment area. The complexity of the development of EG channel and the mechanism causing their formation should also be further studied, such as the quantification of soil detachment and sediment transport mechanisms for both surface and subsurface flows. These processes should be further studied for their effects on gully head advance, sidewall collapse and bed cutting. The comprehensive utilization or application of new methods and technologies, such as automatic technologies, artificial intelligence, machine learning algorithms, would be helpful to improving study efficiency and accuracy. The scientific basis of prediction models was still in need of further development and refinement. Studies filling these knowledge gaps will improve our understanding of EG erosion such that new prediction, and control technologies can be developed.

Technical Abstract: Although concern for ephemeral gully (EG) erosion has been growing among the research community, there still need for a state-of-the-art review to identify knowledge gaps. This study was based on an extensive search of published literature in the Web of Science database. Reviews included papers published in 56 scientific journals over the last 30 years. The main EG erosion topics were related to the gully erosion processes, factors, methodology, models, and effects. The definition of EG was identical worldwide. There is an urgency to define criteria in critical morphological values under different conditions for identification of EG channel locations in fields in order to map and model their development quickly and accurately. Topography factors have been much more studied than other impact factors, including climate, land management, soil, and hydraulics. The interactive effects of different impact factors on EG erosion across various spatio-temporal scales should be further researched. Fifteen different methodological approaches (or technologies), which were categorized into four kinds of methods, including soil monitoring, modelling, simulation experiments, and review, have been employed to assess and quantify EG erosion. The average soil erosion rate of EGs in 36 publications increased and decreased with increase of slope gradients and catchment areas, respectively, and the number of EGs linearly increased with catchment area. The complexity of the development of EG channel and its driving force mechanism should also be studied intentionally, e.g. the quantification of soil detachment and sediment transport mechanisms for both surface and subsurface flow during different sub-processes, including gully head advance, sidewall collapse and bed cutting. The comprehensive utilization or application of new methods and technologies, e.g. automatic technologies, artificial intelligence, machine learning algorithms, would be helpful to improving study efficiency and accuracy. The scientific basis of prediction models was still in need of further development and refinement. This review provides recommendations and suggestions to improve knowledge, prediction, and control of EG erosion.