Rising Sea Level Creates Tough Development Choices

Sea-level rise planning map for State of Maryland. Click for the larger version.

You know those alarming GIS maps that show parts of South Florida or the eastern seaboard swallowed by sea-level rise? You could make a case that they're a bit misleading, because states and local governments are likely to take action to keep waters from encroaching on coastal developments. The questions are, Where should shore protections (bulkheads, dikes, etc.) be utilized? To what extent will they be utilized? And what will be their impacts? A new study and series of maps take this discussion to the next level.

The study, based on a $2 million EPA research project and conducted in collaboration with regional planning councils and 130 local governments in 13 states along the East Coast, mapped out where shoreline protections will likely be added to shield current and future development (under a business-as-usual scenario with current land-use policies), and where land may remain undeveloped and wetlands allowed to migrate inland naturally.

Study authors found that on average, along the East Coast, approximately 60 percent of land within one meter of current sea level is expected to be developed, and will surely require coastal protection over the next century. About 10 percent will be preserved, and the other 30 percent will likely be left undeveloped. In New Jersey, about 81 percent of the land will be developed. A big takeaway: More people are moving to lowland areas that will be inundated with water if left unprotected.

The problems with expanding shoreline protections are numerous. They may put coastal ecosystems in jeopardy, altering wildlife habitat and eliminating wetlands and tidal marshes--which also offer protection from flooding and beach erosion. In fact, the study authors argue, the cumulative effects of shoreline protections could violate the Clean Water Act. And let's not forget about the lessons from Katrina: Coastal barriers can fail catastrophically.

So there are hard choices ahead: deciding which land to give up to the sea and which to fight for; balancing the protection of homeowners with the preservation of habitat. The study's collection of maps for each state will be an asset for planners wrestling with these issues.

Lead study author James G. Titus, the EPA's sea-level-rise project manager, added the following:

The idea [with this study] is to motivate dialogue on where we should protect and where we should allow wetlands to migrate inland. So now, any stories about responding to sea level rise can have two types of maps: the standard elevation or shoreline change map, plus the map delineating the choices.

Titus' findings were published earlier this month in Environmental Research Letters as an article, "State and local governments plan for development of most land vulnerable to rising sea level along the U.S. Atlantic Coast." You can view and download the study results, related resources for scientists and planners, and the entire collection of maps, at http://plan.risingsea.net/.

Charleston, SC, sea-level rise planning map. Click for

larger version.