Published by the American Geophysical Union as part of the "Shor"t Courses in Geology Series, Volume 2.Two major phenomena are making coastal land loss an immediate problem for society. The first of these is the "rush to the shore"--the intense development of coastal areas since World War II. Tens of thousands of vacation homes have been built, the closer to the sea the better (Figure 1). This intensified shorefront development is occurring worldwide, fueled by a combination of population pressures and, in some countries, unprecedented individual wealth and prosperity.