The Hailey-based Wood River Land Trust presented the results of a study of the Big Wood River's historic and present-day channels to the Blaine County Commission Tuesday, raising questions about whether county residents and governments have been good stewards of the prized waterway.
The study was implemented in order to assess the effects of human development over time, prioritize restoration and preservation areas and improve floodplain management strategies. The study's reach extended from the Warm Springs confluence in Ketchum to the Glendale Diversion in Bellevue and included aerial surveys of the river from 1943 to 2006.
"The primary reason for the study was to ensure human health and safety," scientist Cygnia Rapp said. "It is important to arrest what is happening already¾stop road-building and development in certain areas, not just in the floodplain, because floods don't happen only in the floodplain. It is important to judge where the river is going, rather than focus only on where it has been."
Rapp conducted the study and provided a presentation on its findings, which underscored the risks of levee building and rip-rap control on the stream channel, practices which she said have provided short-term controls on the waterway since the mining era, yet decreased stability of the river over time.
Her photos and graphs drew a stark contrast between the naturally meandering channels and highly vegetated islands of the the Big Wood and other rivers in the Northwest as they existed before human encroachment. Rapp extolled the importance of logjams and other woody debris in holding sediments and forming plant and animal habitat in raised islands in the floodplain capable of withstanding two-year floods and taking other larger flows in stride.
County-designated engineer Jim Koonce, who has helped draft county ordinances regarding riparian development for many years, took issue with some of the Army Corps of Engineers data presented by Rapp, saying it was inaccurate in representing erosion statistics along the Big Wood.
"You have a big legal problem because we have allowed millions of dollars of homes to be built on the Big Wood River," Koonce said. "We have locked the river into a meander pattern. Unless you condemn those houses or face monumental lawsuits, you can't let that river do what it wants to do naturally anymore. If you doubt this, wait until one of those billionaires decides to sue you. I think we have been balancing the needs of river protection with private ownership needs for many years and I think we have done a good job. We haven't lost any homes."
Rapp described the Big Wood River fish habitat conditions as "moderate to poor," and pointed out that 40 percent of the study area is leveed or rip-rapped (artificially bank--hardened).
"This is a conservative estimate," she said. "This is a quantitative study only and a lot of these findings need to be 'ground truthed.' But when somebody comes to you and says, 'I lost 20 feet of my property during a flood and need to bring dump trucks in to fill it back,' it's like saying they want to rebuild a hill after a landslide. Levees are not a permanent or long-term solution to risks associated with erosion and flood hazards."
Rapp's study also pointed out that the Lower Broadford Bridge, Star Bridge, and Adams Gulch Bridge are undersized for expected stream flows. Koonce mostly agreed with the assessment, saying, "Just remember that for every foot of span you are talking about hundreds of thousands (of dollars) in cost."
Commissioners Tom Bowman and Larry Schoen pointed to existing ordinances that have prohibited development in the floodplain for many years.
"Perhaps we should just digest this for awhile," Bowman said. "I think it will have applicability when it comes to development and subdivision applications."
Express file photo
The Big Wood River flows through the Wood River Valley.
