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Fragile Fragments
An effort to save dozens of tiny Delta islands before they are washed away by waves and boat wakes got a big boost in February when CALFED agreed to provide $928,000 in construction funds.
The Delta In-Channel Islands project is seeking biologically friendly ways to protect the shorelines of these marshy islands, which are all that remain of the area’s habitat as it was in the 19th century. "These islands are the last refuge for many of the plants that historically populated the Delta," including tules, willows, button bush, Delta tule pea and Mason’s lilaeopsis, says Kent Nelson of the Department of Water Resources. The islands are also stopovers for migratory perching birds, and are used by species of concern such as the Western pond turtle, the giant garter snake, the black rail and troubled Delta fishes.
The fragmentary islands — which were left after dredging barges moved through the area a century ago — have always been subject to tidal action. Historically, however, there was a balance between erosion and sediment deposition. Today, that balance has been upset and the rivers have been isolated from the Delta floodplain by levees, says Nelson. "The most fundamental problem is the large upstream dams that block sediment from coming down river," although the combination of wind-induced waves and heavy boat traffic in the narrow, leveed channels doesn’t help matters. There’s just no room for the water’s erosive energy to dissipate and the unprotected islands take the brunt of it.
The CALFED funding will allow the project — a joint effort of the S.F. Estuary Project, DWR, the Delta Protection Commission, the State Lands Commission, wildlife agencies, the Corps of Engineers, and a team of consultants — to test several erosion control methods on three selected islands, one near Little Tinsley Island and another at Webb Tract. A third site near Webb Tract received a $450,000 headstart in 2000 from DWR’s Delta Levee Flood Protection Program, which values the islands because they provide wave protection for levees.
Among the strategies the project will test are the placement of "brush boxes" around the island. These wooden frames stuffed with willow branches create a permeable but secure wave break, according to Nelson. Old tree stumps, which break the initial shock of wave energy and also allow small fish to hide and feed among their roots, will also be used. The project may also use small amounts of rock to create barriers that divert the water with the highest energy away from the shoreline.
The Delta Protection Commission’s Margit Aramburu gives high marks to the persistence and cooperation of the agencies and individuals involved in getting the project of the ground, although she is frustrated that funding took several years to secure. "This is such a natural project — it’s a no-brainer," she says.
Contact: Kent Nelson (916) 227-7549
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