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Hazard and Risk Evaluation Research Division
Environmental Change Risk Research Field
Keiko Udo (Assoc. Professor)

Research summary


Coastal erosion caused by artificial developments and natural hazards is a serious problem all over the world. In future, sea level rise and extreme weather due to climate change are expected to accelerate the erosion. My study aim to contribute to disaster reduction by developing methodologies to estimate the erosion and to preserve coastal areas.
Figure 1. Map of the Tohoku region and distributions of downward crustal deformation, tsunami watermark height and seawall height, and shoreline retreat due to the earthquake and tsunami in 2011. Significant beach shoreline retreats of several hundred meters, especially in the vicinity of river mouths and seawall breaches, extended over a wide area from Iwate Prefecture to Fukushima Prefecture, causing serious problems in the reconstruction process.
Figure 2. Satellite images of beach erosion due to the 2011 tsunami and its recovery. GPR image along pink line is also shown below. The beach recovered at a significant speed of 25 m month-1 just after the event, but the speed decreased rapidly after several months.
Figure 3. Curve of beach loss rate in Japan for the sea level rise of 0.0 to 1.0 m and future projection of beach loss rate in Japan for sea level rise of 0.6 m. The rate is estimated to be 47% for the sea level rise of 0.26 m (the minimum value of global average sea level rise at the end of 21st century; IPCC, 2013) and 91% for the sea level rise of 0.82 m (the maximum value of the sea level rise). Beaches are important for disaster mitigation, ecosystem conservation, and tourism. Impact of the future sea level rise on coastal area is significant.