The federal government is re-drawing floodplain maps under a deadline that should be pushed back to allow local governments time to evaluate and fix levees. The haste is undue, and the cost of going too fast could be high. Let me explain why. Photo: Andrea Booher/FEMA Nearly one-third of the nation is at risk for flooding, says the National Weather Service. More than 100,000 miles of levees crisscross our country, ranging from sophisticated systems of concrete floodwalls to simple piles of dirt and sand. Each year, millions of homeowners and businesses rely on this under-resourced daisy chain to protect against
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.