Prevention of development could occur through some kind of regulatory fiat, or it could occur through the purchase of properties or the associated development rights. Regulatory prohibition of development occurs most often through setbacks.
Setbacks have a long legal history, and have been used extensively in urban planning and for water quality (stream setbacks in urban areas, for example). Setbacks for the purpose of maintaining a buffer of inundatable lands is fraught with legal issues, however. Setbacks on a street in an urban setting, for example, do not necessarily deprive a land owner of all productive use. A coastal setback could easily do just that, depending on where the setback line was located.
Coastal erosion setbacks have in fact been successfully challenged on takings grounds (see Lucas v. South Carolina Coastal Council). Titus (1998) provides an extensive review of the problems with setbacks and other forms of development prohibition or limitation. It is not likely that setbacks by themselves could be an effective policy tool in insuring the availability of inundatable lands. One of the main problems is that courts, including the Supreme Court, have held and are likely to continue to hold that these kinds of setbacks will require compensation to the landowners for lost economic use.
Aside from the legal and compensatory issues associated with setbacks, there is the practical issue of just where to draw the setback line, given the uncertainty of the magnitude of future sea level rise. Would a new setback line have to be re-established periodically as sea level rose?
Removal of the threat of development of inundatable lands through fee simple purchase or through purchase of development rights or conservation easements is perhaps the most straightforward approach for insuring wetland transgression or inland movement under SLR, but it is also the most expensive option by far and thus of limited utility.
Outright purchase of all of the inundatable lands needed to maintain coastal wetland functions could be extremely expensive. Titus (1998) estimates that a land area the size of the state of Massachusetts would be required to preserve coastal inundatable lands for the entire U.S.
Purchase of these lands should certainly be considered by land trusts interested in preserving coastal wetlands. Many upland areas are no doubt included as buffers in conservation purchases or set asides of coastal wetlands, but there are very few if any instances of land trusts focusing on preservation of inundatable lands. Where inundatable lands are in short supply because of either topography or development, their preservation should indeed be a top priority for coastal land trusts. There are no policy impediments to land trusts and other organizations purchasing these lands. Purchase of inundatable lands, with in-perpetuity conservation easements, would be an excellent use of wetland mitigation resources under §404 of the Clean Water Act. This kind of mitigation would, however, require policy changes at the agency level within the U.S. Army Corps of Engineers, and perhaps even an act of Congress.