Floodwater undermines a bridge abutment and cuts the main road to Vietnam's Nghi Son economic zone

Dang Hong Son, chairman of Thanh Ky commune, told VnExpress and Tuoi Tre that fast water from swollen streams and Yen My lake undermined one abutment at Kim Dong village until it fell, while the opposite end shifted and sank. Tuoi Tre reported that the approach on the side facing the Nghi Son economic zone collapsed completely and that a pier there settled, tilting the main span. Dan Tri saw about 3 meters of abutment in the streambed, broken concrete with exposed rebar and railings dragged into the water.

Weather stations recorded 440 mm at Thanh Tan 1, 403 mm at Nhu Xuan and 323 mm at the Khe Dai reservoir between 7 p.m. on Nov. 8 and 7 a.m. on Nov. 9, according to VnExpress, and more rain was forecast through Nov. 11. The road runs more than 50 km, linking National Route 1 and the Nghi Son economic zone with the Ho Chi Minh road, Tho Xuan airport and the mountain districts of western Thanh Hoa, and it carries freight to neighboring Nghe An and Phu Tho.

Deputy provincial chairman Cao Van Cuong ordered both ends guarded around the clock and told the construction department and the commune to propose an emergency disaster declaration, Dan Tri reported. Once it is declared, the province plans a temporary road to reconnect traffic, then a repair plan for the bridge. Dan Tri also noted a quarry that has been worked for years upstream on the Bai Sim stream; officials have named no cause other than the flood.

Scour, the erosion of soil from around foundations by moving water, brings down more U.S. highway bridges than any other cause, according to a U.S. Forest Service bridge-scour guide. It warns that floods often strip the fill behind an abutment even when the bridge itself stands, and that a lost approach is as dangerous to drivers as a fallen span. Shallow footings and vertical-wall abutments are the most exposed, the guide says.