Cosumnes River Habitat Inspires New Flood Control Solution

Riparian Forests on the Valensin Ranch

Along the wildly beautiful and sometimes rampaging Cosumnes River -- the last undammed river flowing from the Sierra Nevada into the Central Valley -- stately valley oaks thrive in the lush riparian forests and woodlands, remnants of a landscape that was common in the Sacramento Valley a century ago.

In those days, when heavy winter storms flooded the valley, the Cosumnes River claimed its natural flood plains.

Today, agricultural fields and sporadic urban development have replaced most of the riparian forests and woodlands along the Cosumnes River corridor. Levees built by farmers and ranchers decades ago constrict the river, but are essential to hold back periodic flooding from damaging crops and inundating homes.

Breached levee in the Cosumnes River Preserve will not be rebuilt in order to allow the 100-acre cornfield it formerly protected to become natural flood plain.

When worn, weakened levees break, as they did during the New Years flood disaster in January, the Cosumnes River reclaims its flood plain, leaving considerable destruction in its wake. Damage is repaired, flood after flood, at great cost.

New thinking about levees has evolved this year into proposals for non-structural flood control alternatives in the Cosumnes River, guided by nature's own hand.

"The idea is to reduce the velocity of the flood water by enabling the river to expand in its natural channel in certain areas where there isn't development and infrastructure," said Secretary for Resources Doug Wheeler, chair of Governor Wilson's Flood Emergency Action Team. "Allowing the river to flow naturally curtails flood damage, reduces cost, and increases protected habitat and biodiversity."

Nature's Signals

Steve McCormick, regional director of The Nature Conservancy, standing at left, was master of ceremonies May 2 honoring eight individuals for their contributions to acquisition of the historic Valensin Ranch fro the Cosumnes River Preserve. Honored were: Sacramento County Supervisor Don Nottoli, standing at lectern; and, seated from left; Wiley Horne of the Metropolitan Water District; Assemblyman Larry Bowler, R-Elk Grove; State Sen. Patrick Johnston, D-Stockton; California's Secretary for Resources Doug Wheeler; Dave Paullin of the U.S. Fish and Wildlife Service (behind Nottoli); John Schmidt, executive director of the state Wildlife Conservation Board; and Mike Eaton, director of the Cosumnes River Project for the Nature Conservancy.

Flooding is a natural process in the Sacramento Valley during major storms, such as rolled in on New Years Eve. On Jan. 2, the highest peak flow in 90 years punched 23 breaks in aging Cosumnes River levees, flooding Interstate 5, Highways 99 and 16, some 84 homes and 33,000 acres of crops.

Generally, flooding is bad news. The swirling waters destroy homes, crops, and livestock, and create an economic burden to clean up and repair damage and rebuild levees.

But flooding can be good news for biodiversity. Inundation enriches the soil and spreads seeds that generate new trees and promote high quality habitat for birds and animals.