Document Type

Report

Department/Program

Virginia Institute of Marine Science

Publication Date

4-1992

Series

Special report in applied marine science and ocean engineering No. 319

Abstract

The Bank Erosion Study was designed to evaluate eroding fast land bank shorelines as contributors of sand, silt and clay and total nitrogen and total phosphorous introduced into the Chesapeake Bay estuarine system. In addition, the extent and effectiveness of erosion control measures were evaluated for selected shoreline reaches. Fastland banks are the uplands along the shorelines that are composed of semi-consolidated sediments. This study evaluates about 2000 miles of primary tidal shoreline in the Virginia portion of the Chesapeake Bay estuarine system for areas of fast land bank erosion. Primary tidal shorelines are those along the main stem of the Chesapeake Bay and the major tributary estuaries. Approximately 383 miles of shoreline comprising 208 shore reaches are included in. the final analysis. These reaches are responsible for 61% of the annual historic sediment volume loading from tidal shoreline erosion. Sediments for selected representative shore reaches were sampled and analyzed for sand, silt, and clay. Volumetric rates of sediment loading for the study shorelines were determined from historical data. Also, the condition of the shorelines were evaluated by analyzing oblique aerial imagery for 1985 and 1990. From the imagery analysis the extent of defensive shoreline structures (i.e. bulkheads, seawall and revetments) and whether the bank was stable or not was determined. Sediment volume loading was considered to be halted where defensive shoreline structures were installed. There was an increase in shoreline defenses of 18% by 1990. This resulted in an annual reduction of sediment loading by 5%. Total nitrogen and total phosphorous loading from eroding fast land bank sediments have been determined to be significant. This study utilized the results of Ibison et al., 1990 which provided average nutrient loading rates for total nitrogen and total phosphorous from eroded fastland bank sediments. The consequent estimated annual reduction in nutrient loading by defended shorelines for 1990 is about 5% for total nitrogen and total phosphorous. Nineteen reaches have been identified as significant contributors of eroding bank sediments and will require further assessment as to the impacts of nutrient loading.

DOI

https://doi.org/10.21220/V54133

Keywords

Beach Erosion, Tidal Shorelines, Coastal Management, Physical Geography

Funding

This project was funded by the Department of Conservation and Recreation, Division of Soil and Water Conservation to the Virginia Institute of Marine Science utilizing funds provided by the U.S. Environmental Protection Agency, section 319 of the Clean Water Act.