Non-wetland areas will be inundated by rising sea levels with the possibility for the formation of new wetlands. The principal management and policy questions are:
- whether the new inundation will be able to occur on lands suitable for the formation of new wetlands,
- and if suitable, whether that land will be developed and bulkheaded before the inundation occurs, precluding the possibility of the formation of replacement wetlands.
Insuring the availability of inundatable lands inland from existing estuarine wetlands is likely the most feasible adaptation alternative for the vast majority of the Gulf Coast. Inundation is going to occur regardless of the management measures taken, and new wetlands will form given enough time and stability, if the land is there for them to form on as sea level rises. Managed retreat is a passive approach that requires little or no engineering. From the strictly technical, biophysical perspective, it is the simplest approach. Managed retreat, however, is primarily a land use issue with many inherent complexities and potential for conflict. Land use policy is a local and property rights issue rather than a state or federal issue. Insuring that inundatable lands are available will be critical because landward migration will not only be impeded by development. Because of the geomorphic conformation of many bays, abrupt inclines or bluffs will result in total loss of fringing wetlands in some areas until rising sea level breaches the higher level, a gap that could require decades or centuries.
Aside from geomorphic constraints, the main impediment to managed retreat or landward migration of wetlands under sea level rise is not just construction of buildings, but rather, the holding back of the sea through sea walls or bulkheads and their associated fill. A bulkhead confers a degree of permanence not obtained with the simple construction of a beach house on stilts over the natural ground, for example. And once a bulkhead is built, it is reasonable to expect the structure to continue to be built up as sea level rises. No state on the Gulf would require the removal of bulkheads and fill on the bay side even though a rising sea level would have inundated the land at its preconstruction level.
Insuring inundatable lands for the future can be accomplished by preventing development through setbacks or prohibitions, or by modifying the kind of development, particularly in terms of permanence, that can occur in the inundatable lands through rolling easements. This discussion of managed retreat is taken largely from Titus (1998, 2000).
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