Geoprocessing Approaches to Delineate Impoundments and Characterize Subcatchments within Kansas Reservoir Drainages

Abstract

Federal reservoirs in Kansas are presently undergoing infill at varying rates and represent a growing concern, as these features are integral to the state’s infrastructure and projected dredging required to restore capacities are substantial. Kansas exhibits a unique hydrography by having some of the highest densities of small impoundments in the United States. Previous studies have highlighted the potential of impoundments to act as significant sinks for sediment. However, their significance within Kansas reservoir drainages and potential service in mitigating downstream reservoir sediment yields is not well understood. This thesis seeks to improve understanding of small impoundments distributions and significance in relation to reservoir sediment yield through two stages. Chapter 2 applies elevation-based methods of impoundment identification using newly available LiDAR-derived Digital Elevation Models (DEM) in order to enhance Kansas reservoir drainage inventories relative to relying solely on the National Hydrography Dataset (NHD). The two DEM-based methodologies resulted in the identification of features absent in the NHD, and accuracy testing showed both DEM-based methodologies produce more accurate surface area geometries. In turn, the two approaches can be used to update and improve accuracy of inventories relative to using the NHD exclusively. Chapter 3 delineates small impoundment catchment areas within nine eastern Kansas reservoir drainages and compares erosion-related traits in the context of impoundment catchment and direct runoff. The majority of sediment presently infilling Kansas reservoirs has been noted as originating from channel-bank erosion sources, not overland sources. Since impoundments are potentially positioned in the path of channel-bank eroded material, better understanding both their distribution and their potential sediment trapping is an important aspect of reservoir drainage yield modeling and management. By investigating erosion-related factors for reservoir drainages and addressing impoundment catchment, several possible trends were observed. For example, contrasting impoundment size distributions were observed in the highest and lowest drainage sediment yields. Impoundments tend to be more abundant in reaches and grassland areas, while they decrease in abundance closer to reservoirs and in cropland areas. Additionally, average catchment area for small impoundments in the region is much smaller than previous estimates, which may suggest smaller sediment loads reaching impoundments. This thesis demonstrates new approaches to investigating potential trends relating to reservoir sedimentation and suggests several avenues for further research. As LiDAR-derived DEMs become increasingly available, methods such as those demonstrated in Chapter 2 are particularly valuable. Not only does this project highlight potential inaccuracies of the NHD, but it presents automated and easily repeatable methods to enhance NHD-based inventories in other regions. Chapter 3 considers the significance of small impoundments when investigating potential sources of difference in Kansas reservoir drainage yields, which is a component often absent in drainage scale erosion modeling. Given the abundance of small impoundments for the region and the projected costs of reservoir restoration, this study provides insight into the significance of small impoundments in connection to a growing concern. By better assessing the factors responsible for differing rates of infill among reservoir drainages, reservoir drainage management may make more informed decisions. Additionally, this project also capitalizes on the growing abundance of LiDAR-derived DEMs, and demonstrates their value in delineating small impoundment catchment to better understand their role as mitigators of downstream sediment yield.