Record flows on the Big Wood River this spring may have caused headaches for homeowners in the floodplain but the historic event could go a long way towards boosting the overall health of the river, according to the Wood River Land Trust.
After one of the snowiest and wettest winters in 25 years, runoff on the Big Wood peaked at 7.92 feet on May 21, 2006, which was just shy of the May 30, 1983, record of 7.93 feet. But the peak flow, which occurred the same day, trumped 1983 and all other years on record—dating back to 1915—with 7,800 cubic feet per second.
The massive flows seeped into subdivisions, ripped through and devoured tree-lined banks, plowed new channels and blocked off old ones with towering wall-like gravel bars. The end product is miles of virtually new river, which Kathryn Goldman, the land trust's project coordinator, said is like a beloved relative "getting a major face lift."
Brayton P. Willis, a strategic planner with the U.S. Army Corps of Engineers' Walla Walla District, said high flows occurred throughout Idaho this spring but that the Big Wood received Idaho's "High Water Award for 2006."
"It was pretty close to a 200-year event," Willis told a group of land trust donors, Fish and Game officers, and local community leaders on Wednesday during an update on the land trust's three-phase project known as "Healthy Waters, Healthy Future." Launched in 2004, the project will help guide the land trust's efforts to protect and restore the Big Wood and its fish populations.
In June 2005, when the land trust released its findings from the first phase, there was concern that the Big Wood's namesake was in jeopardy, as development and years of drought were limiting the amount of woody debris—critical to fish habitat and overall riparian health—in the river.
"This year's flood event couldn't have been more timely," Goldman said. "It opened a lot of eyes."
Goldman was referring not only to the fact that the Big Wood is once again teeming with big wood, but also that the flood will benefit the land trust's efforts to increase development setbacks in the floodplain—identified as essential to preserving the river's health and status as a world-class fishery.
"We want to leave as much wood in the river as possible," Goldman said. "Taking wood out of the river will do a great disservice to us."
In Phase 1, the land trust compiled scientific data and research on the Big Wood and determined that rip-rap, dikes, unnatural channels, and residential development in the floodplain triggers a significant decline in fish habitat. Allowing the river to function, and fluctuate, in the most natural course possible is key.
In Phase 2, which is now complete, the land trust used GIS (Geographic Information Systems) mapping to identify land-use and river fluctuations over time. They also conducted an extensive education and outreach program.
The GIS mapping revealed that from 1943 to 2004 the Big Wood lost 748.8 acres between Ketchum and the Bellevue area due to encroaching development, which reduced the river's ability to fluctuate laterally, resulting in a net loss of 1.69 miles of river length.
Phase 3, which is kicking off now, will use information gathered in the first two phases to protect and restore the Big Wood. Restoration projects will be driven by the land trust in cooperation with local governments, private landowners, and state and federal agencies.
"We're going to look at the mapping and learn from the flood this year," Goldman said. "Community involvement is going to be key."
Willis said the efforts undertaken by the land trust, which was created in 1993 by a group of concerned local citizens, "are important, crucial and necessary to keep the Big Wood River healthy."