Dam Broke

Consequences of climate change may not be what you think

The dam break in Wisconsin last week that cracked open a couple houses and a sewer line generated some spectacular video, but the damage was minor compared to what could happen as aging dams square off against worsening floods.

Local dams are operating well so far. TVA employs a geek squad to monitor rainfall and adjust dam flows so nothing unfortunate happens, and it will likely be physical deterioration that takes down TVA dams rather than human error. Nonetheless, humans err.

In June 1976, the Teton Dam failed, killing 14 people and destroying much of Rexburg, Idaho as a 39,090-acre impoundment emptied. The breeched Wisconsin dam held 267 acres of water. Small dam breaks can kill, however. When Hurricane Ivan dumped almost two feet of rain in Western North Carolina in 2004, a farm pond in Macon County collapsed and killed five.

The North Carolina collapse was caused by an immense amount of rain. Likewise, in Wisconsin, record rains were the primary cause of damage. Not all flood damage is the fault of chance, however.

Eventually, homes, driveways, parking lots, and roads add up, and less rain soaks into the soil. Streams fill up faster, and the impacts accumulate downstream. Next thing you know, the county is on the hook for water-quality fines and the storm of the century happens every five years. KUB is spending millions to upgrade and repair sewer lines, and they are collecting from rate-payers, not from developers. The county is hiring extra planners and engineers to keep up with all the projects and permits.

Austere politicians like Steve Hall and "Lumpy" Lambert ought to slow down the variances and amendments and giveaways if they really want to cut local spending.

When it comes to wasting money, of course, the federal government knows no equal. A dam in Kentucky was just approved for $317 million in repairs. This is Wolf Creek Dam's second rescue from imminent failure and second permanent solution in its half-century lifespan. Its initial cost was dwarfed by emergency repairs and a $15 million upgrade three decades ago. Dominating nature gets expensive.

Like Teton Dam, Wolf Creek Dam is a span between two soluble rock walls. In both cases, rock was dissolving away along the edge of the dam. In Idaho, the dam failed. In Kentucky, the impoundment was drawn down 40 feet to relieve pressure while engineers inspected the dam. They opted to pump cement into caverns and crevices that had opened up in the soft rock around the dam and build a bigger wall to protect the huge earth embankment from dissolving. Rain is not to blame, nor developers, just poor planning.

Dumb ideas get expensive.

Fortunately, developers are learning how to preserve and restore water resources around construction sites. The mall that will replace the two missing hills near the Smokies' ballpark may actually make the stream in between cleaner. The developer is upgrading drainage for the interstate by adding wetlands to filter runoff, and similar features will control parking-lot runoff. The larger stream will be returned to its natural channel, which was altered when a 1982 World's Fair campground and trout pond was built.

Dams are coming down all over, from farm ponds to industrial and municipal power ponds to main-channel marvels. Some are take-downs to avoid catastrophe; others are efforts to restore hatcheries of shad. The good deeds will need to pick up if we are to stay ahead of the footprint of development.

Excessive development can change the meaning of a 100-year flood, as we are seeing along First Creek. Flooding in the Midwest this year and last exceeded 500-year flood lines and even theoretical maximum flows, so soon we might be talking about millennial storm events. That is when big dams will break. m