Sure thing.
Give me credit with a back link to the page would be greatly appreciated in return.
vic

Hello,

The Geyserville Bridge was replaced in 2006 with the same span footprint as the old bridge that failed. Adding a second west span has not been planned by Caltrans. The reasons for its failure described below are based upon scientific and engineering facts, not conjecture.

The reason for failure of the old bridge was increased scour caused by deflection of flow by the gravel bar and eroding bank upstream. The deflection, called flow "skew" increased scour of the bridge footings by a factor of 4. Also, it has been reported that large trees from eroding banks upstream were caught on the bridge piers which would also increase scour. The build up of the bar upstream was the main cause of failure of a bridge that had existed beyond its useful life.

Adding a span to the west would be a costly project and would involve condemning privates lands, and given that it would not significantly improve flood capacity through the reach, would not be worthy of the cost. The excess gravel building the bar upstream of the bridge would be deposited just downstream where it would only accelerate loss of flood capacity and bar buildup.

The fact is that agricultural lands around the river were reclaimed since the late 1800s to promote agriculture. The river was straightened and deepened by filling floodplain lands and to some extent aided by instream gravel miining. The lackof mining over the past 10 years has allowed the river to reach a point where it will convert to the shallow wide channel it once was and in the process destroy 100s of acres of farmland. Letting the river "go" is a choice where controlling it will be difficult if not impossible without major intervention. Also, money would be spent to cover economic losses rather than towards river management which would include expansion of habitats. Adding a west span would not help river habitats.

Another choice is to skim gravel bars, such as proposed by Syar,  to help maintain flood capacity and channel stability, and to use revenue from gravel to fund restoration projects. The proposed Syar plan would contribute millions of dollars towards fish habitat and riparian restoration projects that the fish experts believe are needed (NOAA National Marine Fisheries Service and California Department of Fish and Game). The Syar project is a sensible approach to managing a problem no public agency is doing anything significant to address.

With Syar's help and urging, Caltrans is working on completing a stream bank enhancement project on the upstream side of the bridge, allowing for a stable bank but one with habitat features such as large wood and an irregular shoreline with riparian vegetation. The rip rap just upstream of the eroding west bank was installed in the 1990s and is now covered in a dense covering of willows and cottonwoods, meaning it has become excellent shoreline habitat. With habitat restoration as part of the project design, the eroding bank upstream of the bridge could be converted from a source of fine sediment pollution from erosion to a stable vegetated bank with deep pools and cover for fish.

If it comes down to how to spent public money and what makes sense, The Syar Alexander Valley Project is a bargain that would result in a coordinated public and private partnership with landowners to address the major issues facing the river. Without the project, a river would be let go to its own devices, which would have catastrophic and costly results.

The decision to narrow and straighten the Russian River in Alexander Valley was made a long tome ago, way before instream gravel mining was implemented. Going back would allow erosion of soils in open vineyard lands, releasing millions of tons of fine sediments. What would be the reaction of private landowners losing their land? To protect and restore their operations, none of which would be valuable for the ecosystem. With cooperation and support of landowners, the present river can be managed to address key habitat problems, such as opening tributary streams to spawning salmon and increasing cold water habitats. Letting the river go accomplishes none of that.

Mitchell Swanson http://SwansonRivers.com

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You make some great points here!