Investigation Report on the Flooding Condition in the Midstream Area of Chao Praya River During the Thai Flooding in 2011

Various investigations about the flood condition and dam operation have been conducted on 2011 Chao Praya river flooding. Investigations about the lower reaches of the Chao Praya river, which was heavily damaged, have been conducted, but investigation reports about the flood form of the midstream Chao Praya river, i.e., upstream where the Ping and Nan rivers meet, have hardly been reported. This investigation sorts out the conditions of flooding and the reservoir of the midstream Chao Praya river and the reflow into river channels fromthe floodplain, which is reflooding, inspects them based on field investigations and considers the possibility of reducing flood damage in the lower reaches using the floodplain in the midstream area.