To many people, coastal land loss is synonymous with beach erosion. Coastal land loss includes beach erosion, but it is a much broader term because it also includes land losses along bluffs and losses of wetlands around interior bays and estuaries. The most important causes of coastal land loss (Fig. 1) are erosion, inadequate sediment supply to beaches and wetlands, and coastal submergence (relative rise in sea level). Any one of these causes may be responsible for most of the land loss at a particular site, or the land loss may be the result of several factors acting in concert (Fig. 2).
The primary causes of coastal land loss include both natural processes and human activities (Fig. 1). These primary causes determine where land will be lost whereas other factors, such as shoreline characteristics, control the rate of land loss. Some agents affecting land loss, such as wave energy, are common to all coasts, whereas other agents, such as vegetative cover, are only of local importance. In most coastal settings, the exact causes of land loss are uncertain, so it is necessary to evaluate all reasonable causes in order to predict what the coast might look like in the future and to understand how land loss will impact coastal communities.
Physical agents affect land losses in all coastal environments, but wetlands are also subject to biochemical reactions and altered water circulation patterns. Because wetlands are unique organic environments, the causes of their deterioration and destruction (Fig. 1) are discussed in a separate section.
This report represents a general overview of the primary causes and consequences of coastal land loss. Most of the examples and references are from states bordering the Gulf of Mexico and the Atlantic Ocean where the largest magnitudes and highest rates of coastal land losses in the United States are recorded (Dahl, 2000). The report serves as an introductory guide to the topics and literature on coastal land loss, and acts as a link to ongoing research being conducted by the U.S. Geological Survey.