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Online backlash after Japan dams discharge water during night Typhoon Hagibis hit

Shiroyama Dam is seen in Sagamihara, Kanagawa Prefecture, in this July 16, 2017 file photo. (Mainichi/Kimitaka Takeichi)

TOKYO -- People took to social media to protest decisions by six Japan dams to enact emergency flood prevention measures over the night of Oct. 12-13 as reservoir levels swelled dangerously due to Typhoon Hagibis.

As their reservoirs approached maximum capacity, the facilities carried out discharges in volumes equal to the amount of water flowing into the dams. Local anger emerged quickly after warnings of the discharges were reported on the news and through other channels on the night of Oct. 12.

Among the concerns expressed online, residents questioned why the emergency water discharges had to be done at night. Others feared that they would not be able to evacuate in the dark in the middle of the typhoon.

According to the Ministry of Land, Infrastructure, Transport and Tourism, emergency water discharges were enacted between 8:50 p.m. Oct 12 and 12:35 a.m. Oct. 13 at six dams in eastern and central Japan: Mizunuma Dam and Ryujin Dam in Ibaraki Prefecture, Miwa Dam in Nagano Prefecture, Shiroyama Dam in Kanagawa Prefecture, Shiobara Dam in Tochigi Prefecture and Takashiba Dam in Fukushima Prefecture.

A car is seen submerged on a flooded road after Typhoon Hagibis struck the area, in Setagaya Ward, Tokyo, on Oct. 13, 2019. (Mainichi/Masahiro Ogawa)

On the decision to carry out the discharges at night, a ministry official said, "We have an agreement to enact the measures once the water level reaches this point. As a result, it went ahead at night."

Among the dams that did release large amounts of water, Kanagawa Prefecture's Shiroyama Dam was reporting for around an hour starting at 12:40 p.m. on Oct. 12 to municipalities along the river basin that it expected to begin the discharges at about 5 p.m.

But rain volume was lower than initially expected, and the plan was scrapped. However, the water level rose after that time, and dam officials announced at about 8:35 p.m. that discharges would have to go ahead at 10 p.m.

However, rainfall increased faster than expected, and between 9:20 and 9:25 p.m., the dam announced it could not wait for 10 p.m. The emergency release of water began at about 9:30 p.m. The decision was conveyed to the public between 9:25 p.m. and 9:35 p.m.

Reflecting on the sequence of events, an official at the prefectural government said, "The influx of water rapidly overtook our predictions, which caused some disarray."

However, even with some municipalities close to the six dams getting as little as an hour's warning of emergency water discharges, the ministry reported as of midday on Oct. 13 that it had not confirmed a single report of property flooding or personal damage in downstream areas.

(Japanese original by Jun Kaneko and Taku Soda, City News Department)

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