Quantifying connectivity and its effects on sediment budgeting for an agricultural basin, Chesapeake Bay Watershed, United States

Abstract

Excessive sediment runoff as a result of anthropogenic activities is a major concern for watershed ecologic health. This study sought to determine the sources, storage, and delivery of sediment using a sediment budget approach for the predominantly pasture and forested Smith Creek watershed, Virginia United States, a tributary to the Chesapeake Bay. Utilizing a novel combination of the Universal Soil Loss Equation (USLE) model and an index of connectivity along with field surveys of channels, this study indicated that streambanks and pastures were major sources of sediment. Overestimation of fine‐grained sediment flux exported from the watershed according to this study's models (3811 Mg/year) compared to export measured at the outlet (2918 Mg/year) most likely indicates underestimation of storage in the watershed from unaccounted for geomorphic features (ponds, toe slopes, and colluvial slopes). Sediment budget results indicating that streambanks are a major source of sediment in the watershed support previous sediment fingerprinting results and provide a framework for managers to address the sediment problem in Smith Creek and similar tributaries to the Chesapeake Bay.

Evaluating water‐quality trends in agricultural watersheds prioritized for management‐practice implementation

“…Streambanks are likely the dominant source of SS in the Smith Creek watershed (Gellis & Gorman‐Sanisaca, 2018). Reducing SS loads in Smith Creek may therefore require MPs that lower rates of streambank erosion (Clifton et al., 2022). Streambanks may be an important SS source in the other study watersheds along with upland soil erosion, which often contribute SS in agricultural areas (Noe et al., 2020).…”

Understanding sediment in river systems—Building on a 50‐year contribution

“…Erosion from cultivated hillslopes, tracks and unpaved roads and channel banks amounted to 1065.4 t year −1 whereas sediment yield at the catchment outlet was only 156.7 t year −1 because of the effects of in‐field deposition, conveyance losses between the field and the valley floor and river channel, and deposition in the valley floor, in the floodplain and in riparian areas and in the river channel. In a sediment budget study of the Smith Creek watershed, Virginia, USA, a tributary to Chesapeake Bay which is under agricultural land use, Clifton et al (2022) highlight the importance of hydrological connectivity and develop a novel combination of a USLE‐type model incorporating high‐resolution topographic and land use data, a surface impedance weighting factor to index connectivity and floodplain and river channel metrics to assess the sources, storage and delivery of fine‐grained sediment. Gurnell and Bertoldi (2022) examine the role of vegetation in fine sediment storage within the active channels of gravel‐bed rivers, an aspect of sediment delivery that hitherto has been relatively little studied.…”