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Photo: Shoreline erosion in North Carolina, coastalgeology. eAINCCOHAZ Along much of the U.S. coast, shoreline changes are related to changes in the shape of the landscape at the water's edge. These changes do not occur as a direct result of sea level rise but rather in response to waves and currents, sediment availability, coastal storms, and human activity, as well as the underlying geology. The complex and dynamic factors contrib- uting to shoreline development make predictions of how shorelines will change in the future (and the rela- tive contribution of sea level rise) difficult and uncer- tain. While current impact assessments often focus on the vulnerability of certain coastal landscapes to inundation due to sea level rise, these models do not incorporate the processes (e.g., barrier island migra- tion) or the environmental changes (e.g., marsh dete- rioration) which may occur (Gutierrez et al. 2009) and may therefore fail to capture the full extent of impact required for local planning purposes. Barrier islands are expected to be disproportionately affected by the impacts of sea level rise. These islands act as an energy buffer, protecting the back - barrier estuarine system from high - energy waves. Because barrier islands occur in areas of large wave energy they are exposed to overwash produced by storms. Overwash acts to erode dunes into the island interior, and sediment deposition from overwash then builds the island's elevation (Gutierrez et al. 2009). As sea level rises, three main processes will affect barrier islands. First, higher sea levels may cause storm overwash to occur more frequently, potential leading to greater erosion and overwash. Second, tidal inlet formation and migration will change future shore- line positions of barrier islands. Third, barrier island shoreline changes may accelerate with rising sea level and stronger storms. Given the dynamic nature of barrier islands, these factors have the potential to leading irreversible changes (Gutierrez et al. 2009), such as landward migration, changes in barrier island size or increases in tidal inlets. Narrow, low eleva- tion barrier islands are most susceptible to increased overwash and may be the first to cross these thresh- olds. The future of these barrier islands depends in part on the ability of salt marshes in barrier lagoons and estuaries to build vertically at a pace equal to the rise in sea level (Gutierrez et al. 2009). However, assessments of shoreline changes on barrier islands indicate that barriers have already thinned in some areas of the country over the last century (Gutierrez et al. 2009). Coastal wetlands are also highly vulnerable to the impacts of sea level rise. Tidal wetlands build verti- cally through the accumulation of mineral sedi- ments and organic matter controlled by a number of processes (Figure 2 -7, Cahoon et al. 2009). Miner- al sedimentation represents the balance between sediment import and export, which varies among geomorphic settings and different tidal and wave energy regimes. Predicting marsh sustainability with given rates of projected sea level rise depends on an understanding of the complex factors that influence wetland development, some of which are them- selves influenced by climate change. In addition to the environmental drivers identified in Figure 2 -7, wetland development is also influenced by barriers to migration, such as human development and topog-