Analysis of the Impact of Water-Supply Outages Due to Multiple Factors Caused by the 2011 Tohoku Earthquake

The Tohoku earthquake, which occurred on March 11, 2011, caused water-supply outages to 2.2 million households in 187 cities and towns. This earthquake impacted on natural and social events, adversely affecting the water-supply system. For instance, there were long-term disruptions of regional water supplies, long-term electric power outages, extensive liquefaction damage, and damage caused by the tsunami. These multiple factors made the damage pattern complex, and water-supply restoration was delayed even though seismic ground motion was moderate. This study attempts to elucidate the factors that caused water-supply restoration to be delayed following the earthquake and to measure the earthquake impact on water-supply outages in terms of restoration time and the households affected by the water-supply outage. As a result, the long restoration time for the water supply following the Tohoku earthquake could be explained by a combination of factors, including restoration time for electric power and regional water supplies and pipeline repair in liquefaction areas, in addition to time for pipeline repair following past earthquakes. Pipeline repair required twice the time compared to past earthquakes.