Assessment of Shoreline Change Knowledge
Shoreline change can be sudden and dramatic, such as on the Gulf Coast after Hurricane Katrina where large portions of coastal wetlands became areas of open water within days. Changes can also be gradual processes where bedrock coasts, like those in the northern Great Lakes, are slowly eroded over centuries. Differences in coastal geology, climate and development mean that erosion and accretion vary widely across the Nation's shorelines.
Before new policies can be recommended, the Corps and its partners must understand the extent of shoreline change and its impacts on different coasts. Examining data on shoreline change is the first step to assessing the effects of erosion and accretion. National Shoreline Management Study (NSMS) researchers utilize state shoreline mapping data and information from Federal agencies including the Corps and the U.S. Geological Survey (USGS). This data is being analyzed in the draft National Assessment and its regional assessments.
Shoreline Change Products
- At the Shoreline Change Conference in 2006, Corps personnel presented "Demonstration of National Shoreline Condition: Gulf of Mexico Pilot Study". This project used a LIDAR-derived shoreline product to describe the shoreline condition. The presentation noted that the variety of shoreline types found just in one state, not to mention within one region, required each coastal area to be examined individually.
- In 2004, the NSMS released a working draft of an inventory of shoreline change data across the United States. This report (pdf, 5.03 MB) assessed the available shoreline change data at the time by each coastal state. The diversity of data in this inventory demonstrated the challenges in developing a large-scale shoreline change database.
- At the Shoreline Change Conference in 2002, the NSMS presentation, "The Use of Shoreline Change Mapping in Coastal Engineering Project Assessment", explained that GIS technology can integrate various forms of shoreline mapping data. Despite challenges with historical sources, understanding coastal change can lead to better design of coastal projects, reduced project costs, and greater environmental and recreational benefits.
Learning from Experience
To understand current shoreline change knowledge, NSMS researchers turned to the last nationwide study of the U.S. coastline—the National Shoreline Study, which was completed in 1971. The National Shoreline Study (NSS) had determined that 2,700 miles of shoreline, about 3.2% of the national total, were experiencing "critical erosion," meaning erosion serious enough to warrant measures to halt it. The study found that these areas of critical erosion were concentrated in the North Atlantic and South Atlantic-Gulf regions, and most areas were directly related to significant shoreline development.
In 2004, the NSMS released a report that analyzed the methods and findings of the National Shoreline Study (NSS). This report found that while the NSS made important contributions to shoreline change knowledge at the time, it did not use consistent criteria or measurements. With new information and data processing techniques, the report stated, the NSMS could make better recommendations regarding shoreline management approaches and government roles.