Last Week, We Were Glad to Have the Damsby Don Brunell
The Columbian, November 14, 2006
While the Democratic tsunami swept across America on election day, Hawaii's "Pineapple Express" pounded Washington and Oregon with some of the heaviest rains on record. It was the worst flooding since 1996.
As bad as the flooding was in communities like Snohomish, Centralia and Tillamook, it could have been worse, considering that none of these communities are protected by dams.
Consider what it was like before many of the dams on the Snake and Columbia Rivers were built. On May 30, 1948, a levee on the flood-swollen Columbia River ruptured. Within a few hours, a 10-foot-high wall of water reduced Vanport, now part of North Portland, into a shattered, muddy ruin. At that time, Vanport was Oregon's second-largest city. The torrent took 16 lives and caused incalculable property damage.
President Harry S. Truman immediately flew west to see the water-logged mess. In Truman's view, this tragedy could have been averted if the Columbia, Snake and Willamette river had been dammed. He told a packed house in the Rose City that Congress must get off the dime and provide the funds for the Bureau of Reclamation to complete its flood control projects on the rivers.
Congress did get off the dime. It built the Dworshak Dam in Idaho to harness the spring torrents of the North Fork of the Clearwater River, a primary tributary of the Snake River which routinely inundated the towns of Lewiston and Clarkston. Congress also funded the construction of the four lower Snake River dams. Those impoundments not only controlled flood waters but opened the Columbia-Snake River System to barge traffic and provide enough electricity to power the Portland-Vancouver metropolitan area.
(bluefish notes: Dworshak Dam provides flood control but the Lower Snake River dams are not operated for that purpose. Converseley, the Lower Snake River dams do provide barge traffic but Dworshak dam is not operated for that purpose. Additionally, Lewiston has levies to protect it from being flooded by the by Lower Granite dam's reservoir.)
President Truman would roll over in his grave today if he saw the legislation proposed by Congressman Jim McDermott (D-Seattle) calling for the breaching of the lower Snake River dams. Unfortunately, after the recent elections, McDermott will chair a House Ways and Means subcommittee that deals with health care and alternative energy. In other words, he will have an important say in future energy policy, and the call for dam breaching may not be a cry in the wilderness anymore.
Reservoirs absorb floods
Consider the consequences if the dams are breached. The impoundment area created by the lower Snake River dams can absorb a huge increase in water levels caused by heavy rains or spring runoff -- 41.7 billion gallons, to be precise. Those four impoundments must maintain a navigation pool with a difference of 4 feet between low- and high-water marks. That 4-foot difference over a combined 100-mile-long and half-mile-wide impoundment area easily absorbed the spring floods of 1996. By contrast that same year, the Touchet River, a tributary to the lower Snake with no flood-control dams, made a sodden ruin of downtown Waitsburg and Dayton.
As our state's population grows, dams become more important for power, irrigation, flood control and navigation. In addition, as our elected officials deal with providing enough fresh water for future population growth, salmon recovery, and irrigated crops, there are proposals to build more storage capacity to capture and store flood waters.
Some of those proposed storage reservoirs are mammoth, like the Black Rock project near Yakima. But not all the projects are in the billion-dollar range like Black Rock. (See Columbia River Reservoir Sites ID'd for Study )
Some are much smaller and could be strategically located in the mountains like a series of beaver dams. In Montana, they call it high-mountain storage. It's a concept that captures part of the heavy runoff before it gathers torrent momentum and saves it for the drier summer months. It then allows the main streams to run unimpeded. That concept could work in flood-prone western Washington and Oregon and prevent the destruction of towns like Vernon, Lynden and Tillamook.
So, as you listen to future debates about ripping out dams, remember that they help prevent flooding. Then imagine what will happen if they're no longer there.
(bluefish notes: ACOE officials have confirmed that Lower Snake dams are not operated for flood control but are kept within four feet of full to provide barge traffic benefits. Storage available in the four feet between low- and high-water marks on Lower Snake reservoirs is 137,400 acre-feet (see Four Lower Snake Dams). A 100,000 cfs increased inflow would raise these reservoirs at a rate of 3 inches per hour giving about 16 hours of storage at this inflow rate. In contrast, ACOE reports that Dworshak dam reservoir "has a gross storage capacity of 3,453,000 acre-feet, of which 2,000,000 acre-feet is used for local and regional flood control" -- about ten days worth of storage capacity at a 100,000 cfs increased flow rate.)
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