'natural dam' means:
a dam made by nature (water, wind, flood, earthquake), not a dam made by man.
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Dams made by Talas to be drained
Kyodo
Temporary roads will be built in Wakayama and Nara prefectures so construction vehicles can dig drainage ditches and prevent two natural dams created by Typhoon Talas from collapsing, the land ministry decided Friday.
The typhoon killed dozens of residents in the two prefectures and triggered mudslides that blocked rivers, forming five natural dams.
Drainage ditches will be dug to drain water from two of the dams in Gojo, Nara Prefecture, and Tanabe, Wakayama Prefecture.
The ministry has warned the dams could break and unleash new floods just as a new typhoon is approaching the region.
Meanwhile, at Nono Elementary School in Nachikatsuura, Wakayama Prefecture, Ground Self-Defense Force troops were piling up sandbags Friday to prepare for potential flooding from the oncoming typhoon. The school building has been designated as a disaster shelter for local residents.
