Floodwaters in rural Minnesota carved a path around a century old dam early last week, causing severe erosion to a riverbank. Several days later, intense rain damaged a dam in Texas. There are roughly 90,000 significant dams in the U.S. More than 4,000 are in poor or unsatisfactory condition and could either kill people or just harm the environment if they failed, according to data from the U.S. Army Corps of Engineers. Many dams are in great shape run by competent operators. But other owners have little money to make needed repairs. States have limited power to force fixes and climate change is making bad rain events in some areas more intense, increasing risk.

Flooding in the Midwestern U.S. has collapsed a railroad bridge and is testing a dam after days of heavy rains that have forced hundreds of people to evacuate or be rescued. The flooding brought additional misery to parts of Iowa, Nebraska, South Dakota and Minnesota as temperatures approached 100 degrees Monday. More rain is forecast, and many streams may not crest until later this week as the floodwaters slowly drain. Governors of the affected states say the flooding has damaged roads and bridges, shuttered or destroyed businesses, required hospitals and nursing homes to evacuate, and left cities without power or drinking water.

BOULDER CITY, Nev. (AP) — A transformer exploded Tuesday at Hoover Dam, producing a cloud of thick, black smoke and flames that were quickly e…