Rehabilitation and restoration of flood-damaged lowlands – an example in the Tokyo Lowlands

Several large rivers are concentrated in the lowlands of eastern Tokyo. The area through which the Sumida River, the Ara River, the Naka River, and the Edo River flow has benefited considerably from the opportunities provided by the waterways, but the area has been impacted repeatedly by floods and high tides. The lowlands of eastern Tokyo have been flooded numerous times. Built in response to historic flooding in the Tokyo lowlands, flood control measures such as channels, dikes and gates have mitigated the impacts of exceptionally high tides. Japan is a country frequently affected by earthquakes. Many houses and people in Tokyo were lost during the major earthquakes of 1703, 1855 and 1923. A major earthquake in the Tokyo lowlands, which lies below sea level, could potentially destroy dikes, subways, lifelines such as electricity and gas, and information networks, affecting the entire country. Therefore, measures to reinforce dikes during earthquakes have been developed. The preparedness and education of residents living in flood-prone areas along the rivers are necessary to reduce concerns in emergency situations. In addition, river facilities such as dikes and gates must be maintained by river managers, and river environments and wetlands must be restored. Keyword: flooding, high tide, lowlands, attitude surveys.