Abstract
In this paper, damage with surface leakage caused by break accident of water supply pipe is interpreted as flood problem. Reduction of flood risk is immitigable. Consequently, assessment for extent of the damage is important before the accident occurs. Urban storm water is drained mainly through sewage system. Even if comparable surface leakage occurs, the damage varies according to conditions, discharge capacity of sewage system and terrain condition. It is estimated that the extent of flood with surface leakage can be larger than that of 50 year return period rainfall through case study analyses. Also, it is suggested that occurrence frequency of surface leakage caused by pipe break accident is higher than by heavy rainfall. Therefore, this paper pointed out the necessity to assess flood risk for replacement planning in the future.
