EROSION OF THE SALT MARSH IN THE FOREST RIVER CONSERVATION AREA, SALEM, MASSACHUSETTS

Salt marshes are important in that they provide many environmental, social, and economic benefits; providing habitat and food for wildlife, recreational and educational opportunities, and protection against flooding and storm surges. Salt marsh loss, in some cases, can lead to flooding, ecologic loss, and pollution of surface waters for the area surrounding the marsh and in turn become detrimental to these benefits. Ortho imagery dating back to 1992 was used to determine the geomorphic change within limited portions of channels within the salt marsh of the Forest River conservation area in Salem, Massachusetts. Using the change in channel width and a measured channel depth, annual erosion rates were determined in order to help assess the cause of changes to the erosion rates within the marsh. For the section of the marsh in this study, erosion rates vary from 0.47-8.3 cubic meters per year since 1992. At this time, there is no clear correlation between the variable erosion rates and changes to sea level. However, rising sea level is likely to be enhancing salt marsh erosion throughout the region. Past studies of the Forest River salt marsh have shown elevated levels of toxic metals in the surface sediments of the marsh. Increased amounts of erosion could be redistributing contaminated sediments throughout the estuary that can be harmful to the ecology at the deposition sites. More work is needed to determine if erosion rates of marshes throughout the region are similar over the same time period.