Century-scale shoreline changes of five beaches in JAPAN

Coastal erosion caused by sea level rise is a serious problem for people all over the world. Global sea level will rise from 0.18 to 0.59 m (IPCC, 2007). Along the coasts in Japan, sea level will rise from 0.09 to 0.27 m by the end of this century. The future estimation considers only thermal expansion due to rising sea temperature caused by global warming. However, considering the contribution of scale-down of Greenland and Antarctic ice sheet, there is potential of the increase in the rate of sea level rise. There are few studies which evaluate impacts of the future beach erosion on society by comparing with the past shoreline change resulting from natural forces and human activities. This study evaluates the long-term shoreline changes due to natural forces and human activities by using old maps. Shoreline changes were influenced by natural forces from 1900 to 1950 and were influenced by human activities from 1950 to 1990. Shoreline changes showed that the changes tended to be stable after 1990, and coastal erosion due to climate change would likely become obvious in the future.