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Coastal erosion in CaliforniaWithin the next 60 years, coastal erosion may claim one out of four houses within 500 feet of the U.S. shoreline.[1] Coastal erosion is caused by rising sea level, powerful ocean waves, large storms, and flooding.[2] Coastal erosion affects businesses, homes, public facilities, beaches, and bluffs close to the ocean or Great Lakes.

Inasmuch as paleo-environmental and historical data have clearly indicated the occurrence of sea-level changes in the past, new scientific information on the nature and causes of sea-level change- and the development of a quantitative predictive capability- are of utmost importance for the future. This topic is inherently an interdisciplinary science problem addressed within NASA by the Cryospheric Science, Ocean Science, Hydrology, and Solid Earth Science Programs.

The 10–20 cm global sea-level rise recorded over the last century has been broadly attributed to two effects: the steric effect (thermal expansion and salinity-density compensation of sea water) of changes in global climate, and mass-budget changes due to a number of competing geophysical and hydrological processes in the solid Earth-atmosphere-hydrosphere-cryosphere system. While the steric effect is primarily a climatic issue, the Solid Earth Science Program is poised for a fundamental contribution by separating the two effects via a combined use of space geodetic measurements of sea-surface topography and timevariable gravity.

The mass-budget changes include water exchange from polar ice sheets and mountain glaciers to the ocean, atmospheric water vapor and land hydrological variations, and human effects such as water impoundment in artificial reservoirs and extraction of groundwater. These exchanges are all superimposed on the vertical motions of the solid Earth due to tectonics, rebound of the lithosphere from past and present deglaciation, and other local ground motions. A number of space geodetic measurements of sea-surface topography, ice mass, gravity, and ground motions are directly relevant. A complete knowledge of sea-level change will then emerge and be used for the development of predictive global and regional models.

Scientific challenges   FEMA study
Effect on society   Coastal erosion map
NASA's applications   Integrated Solid Earth Science Program



[1] "Significant Losses From Coastal Erosion Anticipated Along U.S. Coastlines," Federal Emergency Management Agency - June, 2000

[2] See reference #1

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