Thesis
Ephemeral gully location prediction and erosion susceptibility modeling using GIS techniques
Washington State University
Master of Science (MS), Washington State University
05/2021
DOI:
https://doi.org/10.7273/000004257
Handle:
https://hdl.handle.net/2376/124996
Abstract
Ephemeral gullies (EGs) are a major source of sediment transport from agricultural land. We need to be able to locate EGs in order to identify erosion susceptibility and to assess sediment loads from agricultural fields. The main goal of this study is to predict EG location and erosion susceptibility in agricultural fields in the Palouse river watershed. I evaluated four topographic index (TI) models to predict EG locations: Slope Area [SA], Compound Topographic Index [CTI], Soil Wetness Index [SWI] and Topographic Wetness Index [TWI], by applying the threshold concept (T values), which specifies the location or pixel in watersheds where gullies develop. Model predicted EGs location were compared with observed EG locations by using visual interpretations and error matrix analysis. I investigated EG erosion susceptibility based on predisposing factors related to topography, hydrology, and soils by applying a weights of evidence (WOE) bivariate statistical model. In total, 372 EGs were mapped and separated into a training set (70%) and a validation set (30%). The chi-square conditional independence test among the factors resulted in 12 test susceptibility models of independent predisposing factors. TWI and SA models predicted EG locations better than the CTI and SWI models. The 10m DEM predicted EG locations better than the 30m DEM. The TI models better predicted EG locations and areas with runoff generation resulting in the significance of slope and drainage area relationships in the landscape. The WOE modeling improved understanding of EG erosion risk areas and can be beneficial to conservation planners and landowners to minimize future erosion losses with the use of best management practices to keep our soil healthy and the land more fertile. This study has provided important insights in identifying the role of factors contributing to EG erosion in the study watersheds such as gentle slopes, high precipitation amount, proximity of fields to roads and streams, Palouse and Thatuna silt loam soils, high elevation areas and, most significantly, agricultural land. Overall, results from this study compare well with similar EG studies and should be useful for understanding gully erosion in hilly terrain
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Details
- Title
- Ephemeral gully location prediction and erosion susceptibility modeling using GIS techniques
- Creators
- Trupti Lakhkar
- Contributors
- Jan Boll (Advisor) - Washington State University, Civil and Environmental Engineering, Department of
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Identifiers
- 99900896416701842
- Language
- English
- Resource Type
- Thesis