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Like Water for Concrete 

From flood control to watershed management

Wednesday, Aug 8 2001
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THINK "WORLD PEACE," "INFORMATION AGE," "ICE CREAM" -- "watershed management" may be a dry term, but few two-word phrases promise so much to so many.

L.A.'s water troubles, in brief: too little water in the L.A. basin, too much floodwater in the rivers.

Flood control -- or L.A.'s approach to it, with concrete river channels and storm sewers -- has made both troubles far worse. It drains water from across the L.A. basin and puts it . . . where? In the rivers. So floodwaters swell. L.A. has to import water. And water quality plummets, because pollutants wash straight into the rivers (to the ocean) rather than into the ground, where water self-cleans. In sum, it's an insane way to make the water go 'round in our beloved semiarid, flood-prone basin.

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Watershed management would restore the basin's natural hydrology -- to maximize water supplies and quality as well as flood protection. Such strategies as cisterns, wetlands, trees and permeable surfaces capture storm water where it falls, where we can recycle it right away or let it sink back into the aquifer. Far less water enters the rivers -- and during floods, diversion basins and channels where necessary can contain the rest. And we get parks, wetlands, habitat and clean, low-cost water all over the place.

And then . . . some of the concrete can come out. Advocates disagree on how much, and how soon. Ten years? Fifty years? A little right now? Most agree that to dynamite concrete by the mile is a very long-term goal, but that we can connect enough of the river back to its watershed to restore the health of both. You don't have to remove every inch. In fact, advocates generally see the ultimate measure of a healthy L.A. River as the return of the steelhead trout.

Barriers to this transition include scarcity of available riverside lands (for wetlands restoration and diversion lakes) and a vast basin of impermeable pavement. But in the past year, a few armies' worth of public agencies and nonprofits have set out to collaborate on detailed watershed plans. In the surest sign of a revolution, L.A. County's Department of Public Works -- long the Sun God of Flood Control -- reorganized in 1999 to create a Watershed Management Division. And the engineers up in that tower in Alhambra are serious about it: They win raves on the many projects they're leading or helping out on. The studies will be complete in 2001°©2003. Land purchases and pilot projects, already under way, should multiply rapidly.

Let the transition begin! These are the first projects:

Upper watershed. The massive existing flood-control system includes concrete-channel tributaries, spreading grounds, and dozens of dams and detention basins in the uplands that drain into the river. Projects to restore the upper watershed to health include greening the diversion basins, removing exotic plants that either choke the channels or soak up unusual amounts of water (or both), and releasing floodwaters on a schedule that will enhance wetlands habitat downstream. The county is also eyeing sites to remove concrete.

Sepulveda Basin. The 2,000-acre detention basin behind the Sepulveda Dam -- flooded only during unusually heavy rains -- has doubled as a recreation area since the late 1950s, with wetlands restored in stages since 1979 (see The Valley). The Bureau of Sanitation wants to construct a 50-acre wetland, with plants that bind pollutants, to clean Tillman water to new state standards. In the multipurpose spirit of watershed management, the design makes the wetland a wildlife area with trails, bike paths and views. If it works, the bureau will construct 500 acres in all. (ETA start 2003) And the Army Corps of Engineers plans to restore a 28-acre chunk of habitat along Bull Creek, with trails and natural-history info. (ETA start 2002)

Tillman Water Reclamation Plant. The treatment plant, which cleans San Fernando Valley wastewater to a tertiary standard (wade in it, but don't drink it) and releases it into the river, is now actually the source of most of the river's dry-season flow -- which means that, until L.A. can supply its own water, much of the river water originates in other watersheds.

Tujunga Wash. This 1-plus-mile greenway/bikeway will connect a major tributary back to the basin not by dynamiting the concrete, but by diverting water into a new, parallel streambed -- see the Lower Arroyo Stream Restoration for a precedent. It's brought to you by the Santa Monica Mountains Conservancy, County Public Works and Zev Yaroslavsky's 3rd District, which would like to see the greenbelt in this park-deprived area expanded along the entire 9-mile wash. (ETA start 2002) The River Project, meantime, is doing a hydrodynamic model of the entire wash, to identify sites where concrete removal would be feasible. (ETA 2001)

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