High Flood Risk Acknowledged in Advance in Badly Hit Area in Okayama

July 11, 2018

Okayama- The danger of flooding in the Mabi district in the city of Kurashiki, Okayama Prefecture, had been well acknowledged before the district was submerged in water in the latest rain disaster.

Dozens of people have been confirmed dead in the district, which was massively flooded by torrential rain that mainly lashed western Japan through last weekend.

Nearly 30 pct, or about 1,200 hectares, of Mabi was swamped, affecting about 4,600 houses, after the embankment of the Oda River burst 3.4 kilometers upstream from the point where the river merges into the larger Takahashi River.

Shiro Maeno, Okayama University professor in river engineering, pointed out that the embankment collapsed probably due to the so-called backwater phenomenon, in which a rise in the water level spreads from downstream to upstream.

According to the land ministry's Chugoku Regional Development Bureau, the Oda River's water level tends to become higher around the merging point because of a slower stream and the existence of a curved section.

The ministry was to begin work to expand the width of the Oda River this autumn and give a full boost in fiscal 2019 and later to a project to lower the river's water level by moving the merging point 4.6 kilometers down the stream.

Maeno said the flood disaster might have been reduced if the project had been completed. Jiji Press