- Causes of Future Sea Level Rise
- Elevation Maps
- Will we really lose all that land?
- Sea Level Rise Planning Maps
Rising sea level inundates low-lying areas, converts wetlands to open water, erodes beaches, exacerbates flooding, and increases the salinity of estuaries and aquifers. Here are some reports that examine coastal wetland loss as sea level rises.
Evolution of a Marsh as Sea Level Rises
Coastal marshes have kept up with the slow rate of
sea level rise for the last several thousand years. Thus the area of mash has expanded as new lands
lands were inundated. in the future, if sea level rises more rapidly than the land surface of the marsh,
the area of marsh will contract, reversing the expansion of the last several thousand years. Where bulkheads
are built just inland of the marsh to protect coastal development, wetlands may not be able to migrate
inland and be totally lost..
Tidal wetlands are generally at an elevation between mean sea level and spring high water (the average high tide during new moons and full moons). So one might expect that in an estuary where spring high water is two feet above mean sea level, a two foot rise in sea level would drown all the existing tidal wetlands, while creating new tidal wetlands in the dry land that had been less than two feet above spring high water. If this occurs, a large portion of the wetlands will be lost because the land within two feet above spring high water is generally a small percentage of the area of tidal wetlands. The ratio of the area of wetlands to the area of dry land low enough to become wetland is called the topographic vulnerability of the wetlands. If part of that low land is developed and protected from the rising sea, however, the actual land available for wetland creation is less than suggested by topography alone.
Fortunately, the surface of the wetlands often rises along with the sea, because marsh grasses trap sediment and create peat. The elevation of wetland surfaces is often called "wetland accretion" (but beware: the term "wetland accretion has some other meanings as well). If the wetland surface keeps pace with the rising sea, no wetlands will drown and the area of wetlands will increase as low lands are submerged and convert to wetland. But if sea level rises too rapidly, the existing wetlands will convert to open water and the newly submerged lands will account for most of the remaing area of wetlands. Most wetlands are able to keep pace with the current rate of sea level rise, but would not be able to keep pace if sea level were to rise three feet in the next century. The figure to the right summarizes the relationship between topographic vulnerability, shore protection, and wetland accretion. Because these three sources of wetland vulnerability require three very different skill sets to assess, many studies evaluate one of these three factors in detail while making rudimentary assumptions about the others
Reports and other products
- Maps showing topographic vulnerability of coastal wetlands. Figure 2 of the maps were in a 2008 EPA report but for the most part these are unpublished maps.
- Maps of Lands Close to Sea Level along the Mid-Atlantic Coast: An Elevation Dataset to use while waiting for LIDAR (PDF) (44 pp., 2,150 KB) U.S. Environmental Protection Agency. From Background Documents Supporting Climate Change Science Program Synthesis and Assessment Product 4.1: Coastal Elevations and Sensitivity to Sea Level Rise - U.S. EPA, EPA-430-R-07-004 (2008). This paper documents EPA's $1 million Bush-era elevation study, which was designed to estimate the topographic vulnerability of tidal wetlands. (EPA has not published the maps but this web site pprovides many of them.)
- Tables showg area of wetlands and low land by county and state. These tables quantify the area of tidal wetlands and the vulnerable land based on the maps created during the Bush-era study. The tables provide uncertainty ranges based on the design accuracy of the data used to create the maps. One can use these estimates to calculate the average topographic vulnerability of tidal wetlands for any county. A summary maphas all the counties in the mid-Atlantic.
- The first nationwide assessment of the impacts of sea level rise. The primary focus of study was to estimate land loss, wetland loss, and the cost of holding back the sea, for inclusion in Chapter 7 from EPA's 1989 Report to Congress: Potential Effects of Global Climate Change on the United States EPA-230-05-89-052 (1989) About one third of the study's budget was on Dick Park' effort to estomates wetland loss. The study Park's (then) new SLAMM model, which largely focussed on topography (though it also included crude assumptions about wetland erosion, accretion, and shore protection). The report's overview paper combined the sites to develop an estimate of the nationwide loss of wetlands.
- Greenhouse Effect and Sea Level Rise: The Cost of Holding Back the Sea - Coastal Management, 19:171-204 (Abstract), (html), (pdf) (1991). This article summarizes the sea level rise study conducted for the Report to Congress.
Wetland Vertical Accretion
- Wetland Sustainability summarizes what wetland scientists think about the impact of sea level rise on tidal wetlands. The article was a chapter in the Bush Administration's official literature review of the impacts of sea level rise entitled Coastal Sensitivity to Sea Level Rise: A Focus on the Mid-Atlantic Region - U.S. Climate Change Science Program (2009) The chapter does not quantify wetland loss from sea level rise, and suggests that most previous efforts to do so were questionable at best. Nevertheless, it does offer predictions about which coastal wetlands will be converted to open water because they will be unable to keep pace with a rising sea.
- EPA's Bush-era assessment of the ability of tidal wetlands to keep pace with the rising sea. Two papers from Background Documents Supporting Climate Change Science Program Synthesis and Assessment Product 4.1: Coastal Elevations and Sensitivity to Sea Level Rise - U.S. EPA, EPA-430-R-07-004 (2008). The first paper explains the wetland processes and summarizes the expectations of an expert panel, while the second paper creates maps and a GIS data set that summarize those expectations. These papers are the basis of a widely reproduced map depicting the ability of mid-Atlantic wetlands to keep pace with rising sea level. 1987.
- Saving Louisiana's Coastal Wetlands: The Need for a Long-term Plan of Action - U.S.EPA and Louisiana Geological Survey, EPA-230-02-87-026, April 1987).
Will development and shore protection prevent wetlands from migrating inland?
- State and Local Governments Plan for Development of Most Land Vulnerable to Rising Sea Level along the U.S. Atlantic Coast - Environmental Research Letters (2009)
- Rising Seas, Coastal Erosion, and the Takings Clause: How to Save Wetlands and Beaches Without Hurting Property Owners - Maryland Law Review, Volume 57, 1279-1399 (1998). Explores how to keep shore erosion from eliminating estuarine beaches given the tendency to erect shore protection structures. Shows the similarity between what had been called "presumed mobility" and the rolling easement of Texas common law and suggests that all such policies be called "rolling easement".
- Does the U.S. Government Realize that the Sea is Rising? How to Restructure Federal Programs so that Wetland and Beaches Survive (PDF, 68 pp., 4.3 MB) - Golden Gate University Law Review, Vol. 30, Number 4 (2000). Focuses on the ways that the federal government policies might help wetlands to migrate inland
- Anticipatory Planning for Sea-Level Rise Along the Coast of Maine - Maine State Planning Office and U.S. EPA, EPA- 230-R-95-900 (1995). The report discusses and evaluates the costs of possible policies to allow wetlands to migrate inland, concluding that rolling easements are cost effective.
- Greenhouse Effect and Coastal Wetland Policy: How Americans Could Abandon an Area the Size of Massachusetts at Minimum Cost - Environmental Management, Vol. 15, 1:39-58 (1992) ((html) (pdf)). This report compares various options for allowing wetlands to migrate inland, concluding that in most cases the "presumed mobility" approach (later called "rolling easement") costs least
- Maps that Depict the Business As Usual Response to Sea level rise in the Decentralized United States of America Originally published by Organisation for Cooperation and Development. Global Forum on Sustainable Development: Development and Climate Change - Background Papers (2004).
General reports on wetland vulnerability to sea level rise
- Greenhouse Effect, Sea Level Rise, and Coastal Wetlands - U.S. EPA, EPA-230-05-86-013 (1988).