Last Saturday, towns in Iowa experienced the results of a spectacular dam failure. The Lake Delhi dam, overwhelmed by flooding from the Maquoketa River, gave way, and within hours the nine-mile-long lake had nearly drained, leaving boats resting on dry ground and lakefront properties perched precariously on the eroding shore. Portions of a road on top of the 55-foot-high dam were washed away.
The damage turns out not to be as bad as it might have been, given the magnitude of the failure—although that’s small consolation to those whose homes and businesses were destroyed. Parts of Hopkinton and Monticello were evacuated as the river downstream of the lake flooded, fed by the escaping water. Monticello’s sewage treatment plant shut down, and property damage was estimated to be in the millions of dollars, but no injuries were reported.
The Federal Emergency Management Agency has been reamapping flood zones, and federal rules require dams, dikes, and levees to be certified; if they aren’t—for example, if a structure is old and its engineering documents can’t be located—the areas downstream are considered to be in a floodplain. Among other things, that makes it hard for property owners to get flood insurance. Based on interviews with area residents, it seems many didn’t have—and hadn’t sought—insurance, believing they weren’t at risk. One report stated that the dam had been inspected in May of last year by the Department of Natural Resources, which found no major structural flaws.
The lake was created in the 1920s as part of a hydroelectric project. The hydroelectric plant no longer operates, but the lake has been used for recreation.