Impact of Shoreline Stabilization Structures on Chesapeake Bay Nearshore Habitats

Abstract:

Currently 69% of Maryland’s shoreline is eroding and 12% is hardened with increasing rates of hardening occurring as development progresses. Shoreline erosion rates are likely to increase, and community needs for shoreline protection are likely to become more important as rates of sea-level rise increase with climate change, constituting a serious coastal hazard. However, the effects of different shoreline stabilization structures on erosion and nearshore water quality and habitat are complex. A variety of stabilization techniques are used in the Maryland Chesapeake Bay, and while the qualitative effects of the different techniques are generally known, there is little quantitative, long-term information available. This study has developed a comprehensive data set comparing long-term impacts of different shoreline stabilization techniques on both the physical environment and habitat. These data include shoreline and bathymetric surveys for comparison to pre-installation information, comparison of pre- and post-construction submerged aquatic vegetation (SAV) coverage, field surveys of SAV and marshes, and collection of cores to determine changes in sediment characteristics and accumulation rates. We have also assembled available estimates of wave and tides near each site to construct wave-sea level climatologies for use in a semi-empirical model of erosion potential. Statistical tests are used to explore relationships among variables. Preliminary results suggest that sediment characteristics depend on the source of material – shoreline type and estuarine salinity zone (proxy for fine sediment availability) – whereas sedimentation rate depends on structure geometry and the pre-construction sedimentation, which generally reflects physical processes controlling sediment transport. Also, sediment type, rather than structure type, seems to influence SAV (plants need sand).