| If a dam incident occurs, it may release a large quantity of stored water which then flows downstream, causing severe damage to the downstream region, so it is essential to continuously and strictly manage the safety of dams. Measurements together with visual inspections can reliably confirm the safety of the dam body and its foundation.The management of dam safety in Japan is stipulated in the Cabinet Order concerning Structural Standards for River Management Facilities, etc. [1], which specifies the minimum, or most important, items that must be measured to manage the safety of dams.Japan constructed many large dams during the 1960s and 1970s, and thus many dams are approaching their fiftieth year since completion. Fig. 1 shows the change over time since 1950 in the number of years since completion of existing dams, including planned dams at the end of 2007. Dams which havebeen in service for 50 years or more accounted for 45% of all completed dams in2010, and will reach 58% by 2020.While the number of aged dams is inevitably rising, the budget for managing them is shrinking, reflecting the harsh financial circumstances in Japan. The facilities at some dams have deteriorated, preventing appropriate safety management, but dams are vital infrastructure that must be used effectively, so it is necessary to appropriately manage their safety.This paper introduces the present state of the safety management of dams in Japan, and then outlines the problems involved and the measures being taken to solve them. |
