NERRS banner

Graduate Research Fellowship
The effects of seawalls and berms on salt marshes: Implications for marsh persistence and restoration of self-maintenance

Catherine Bozek
Graduate Research Fellow 2002-2003
Great Bay, NH
University of New Hampshire

The purpose of this study is to examine the effects of man-made barriers, such as seawalls and berms, on salt marshes in the Great Bay Estuary of New Hampshire. Effects on sedimentary processes due to wave reflection off of the structure will be examined by using marker horizons and grain size analysis. The influence of seawalls and berms on wrack cover will also be assessed. Well transects will be installed to determine if seawalls and berms have an effect on fresh groundwater inflow to the marsh. The impacts of wave reflection, wrack burial, and groundwater flows on salt marsh vegetation will be assessed by studying the plant populations along transects in areas with and without man-made structures. The process level results examined at specific sites will be interpreted in the larger context of the distribution of barriers in the Great Bay Estuary, N.H., and implications for the future persistence of salt marshes adjacent to these structures will be assessed. Biodegradable wave buffers may help to lessen wave energy and decrease erosion due to wave reflection. Buffers will be installed at selected sites and the success of vegetation transplanted to the area will be assessed.

This project is significant on many levels. First, a basic understanding of the processes occurring in marshes near seawalls and berms is needed. The effects of these processes on natural salt marsh plant diversity can then be determined. These effects can be applied to marshes within the Great Bay Reserve, as well as marshes throughout the Great Bay Estuary and potentially to all salt marshes in New England. Understanding the effects of seawalls and berms on salt marshes will help managers guide regulation of these structures in the future.
Return to Project Abstracts