Levees near fields collapsed
Two mega solar power plants, one with an output of 1.35MW and the other 1MW, were damaged by the disaster (Fig. 3). Levees of nearby rivers collapsed, and muddy water and driftwood rushed into the plants. The fences, mounting systems and solar power generation equipment were destroyed or submerged underwater because of the disaster.
These mega solar power plants are located near the point where the Tottabetsu and Satsunai rivers meet and stand between the two rivers.
The two rivers are administered by different entities. The Satsunai River is administered by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) while the Tottabetsu River is administered by the Hokkaido Government. In respect to the collapse of levees of the Satsunai River, the Obihiro Development and Construction Department at the Hokkaido Regional Development Bureau of MLIT presented the progress and measures in September 2016 (Fig. 4) (See related article).
The levee on the right side of the Tottabetsu River, which is administered by the Hokkaido Government, collapsed first. The levee was destroyed for a distance of about 500m, according to reports (Fig. 5).
The destroyed portions are located between the Tottabetsu and Satsunai rivers. Fields, agricultural warehouses and mega solar power plants are between the two rivers and were damaged by flooding caused by the collapse of the levees.
When the levee on the right side of the Tottabetsu River collapsed, water containing soil and driftwood flowed from the Tottabetsu River into the area between the Tottabetsu and Satsunai rivers.
The majority of the areas near the collapsed portions along the Tottabetsu River are occupied by fields, and beets from which sugar is produced and potatoes were grown on the fields. The floodwater reached the mega solar sites, eroding the soil and covering the beets and potatoes.
The water from the flooded river flowed mainly to the southwestern side of the mega solar power plants. The fences and mounting systems blocked the entry of some driftwood, beets and potatoes, but the force of the water didn't wane and the water flowed further toward the north.
The water reached the area near the point where the Tottabetsu River joins the Satsunai River. The floodwater that reached this area destroyed the levee of the Satsunai River, flowing from the land side (Fig. 6).
The levee on the left side of the Satsunai River was destroyed for a distance of about 200m in the area adjacent to the point where the Satsunai River joins the Tottabetsu River, according to the announcement by the Obihiro Development and Construction Department of MLIT.