In July 2004, torrential rain induced by baiu.front caused devastating floods in the Asuwa River basin damaging five railway bridges between Fukui and Miyama stations on the JR Etsumi Hoku line. The Asuwa River basin has only one river gauging and two AMeDAS ground rainfall measuring stations. Those limited data are not sufficient to forecast the heavy floods caused by unprecedented downpours. A physically based distributed TOPMODEL with Muskingum-Cunge flow routing method and radar derived rainfall intensities are used to simulate hydrological processes of the basin. Results show good agreements with observed discharges at Tenjinbashi gauging river station. Simulated distributed discharge values are used to compute the bending stresses of the collapsed railway bridge piers and compared with respective bearing capacities. The main objective of this paper is to introduce the state of art of distributed hydrological modeling with radar derived rainfall inputs to identify the river structures along the river channel that are vulnerable to floods.