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Protecting the Floodplain Part of Water Management

Chico Enterprise-Record - March 2, 2017

By Irv Schiffman

A startled heron springs into flight from a small island during a high-water excursion with Sacramento River Eco Tours last year. Photo by Bill Husa, Chico E-R

Is it wet enough for you?

The recent and unexpected rains may have ended the drought in a good part of California — certainly in our area — but they are not an unmixed blessing. With the heavy rains comes the likelihood of f loods and our part of the state is particularly susceptible to flooding. You may remember that the last major flood in Northern California, in January 1997, did most of its damage on the Feather River.

Gov. Jerry Brown surprised people when he announced as part of his 2015 billion- dollar drought relief program that $600 million would be spent on flood control measures.

“With climate change and global warming, there will be more extreme weather events,” Brown said. “All of a sudden, when you’re all focused on drought, you can get massive storms that flood through these (river and stream) channels and overflow and cause havoc.”

The fact is, drought or no drought, scientists tell us that due to climate change California’s wet season will become shorter and sharper. Storms are likely to be more intense, and winter precipitation will more likely fall as rain rather than snow — the perfect recipe for flooding.

The risk of new and dangerous floods, whether brought on by global warming or a normal weather cycle, gives emphasis to the importance of floodplains. Floodplains naturally serve as a buffer from catastrophic flooding. Though their value often goes unseen, floodplains slow and absorb tremendous amounts of what would otherwise be destructive floodwater and at the same time recharge — especially now in the Central Valley — a depleted groundwater system.

However, the rich soils and presence of water that make floodplains biologically rich, are also great for agriculture. Much of the floodplains in our Central Valley have been converted into farmland. Such conversion often leads to a leveling of the floodplain and the replacement of the riparian vegetation with a vegetation pattern composed of one crop species. When this occurs the floodplain loses its natural connection to the river and can no longer serve as a safety valve when the river reaches f lood stage.

As for farms located on the floodplain, floods can be physical and economic disasters. The floodwaters carry river debris that must be cleared and farm equipment must be cleaned or salvaged. Plants that are not destroyed must often be discarded. Farmers operating on narrow margins must find a way to make up for lost revenue and pay for damages to land and equipment. Water that stays on the farm for two or three weeks can eat away at the levee through wind wave action, contributing to eventual levee failure.

To prevent disastrous flooding where farms occupy the floodplain, it’s necessary to reconnect the floodplain to the river. In the Central Valley, that usually means replacing farmland with riparian vegetation and in some cases constructing a setback levee to allow additional floodwaters to flow slowly over the expanded floodplain. In the past 20 or so years, state and federal agencies and non-profits, such as River Partners and The Nature Conservancy, have acquired over 12,000 acres of land along the Sacramento River from Colusa to Red Bluff, acreage that has, or will be, converted to its original floodplain function.

Changes in federal and state laws require that flood reduction be combined with ecosystem restoration so that f lood control projects have become multi- objective and multi- partnership efforts. A present example of a multiobjective and multi- partnership project is the collaboration between the U. S. Army Corps of Engineers, River Partners, The Nature Conservancy and Reclamation District 2140 to provide flood protection to the residents of Hamilton City. The City has relied on the privately and poorly built “J” levee to contain flows from the Sacramento River causing residents to be evacuated six times in the past 24 years. Finally, after years of advocacy, the federal government agreed to finance the construction of 6.8 miles of setback levees to provide a more reliable form of flood protection to the community and surrounding agricultural areas.

River Partners was chosen by the Corps to carry out the restoration work on 925 acres between the new levees on land donated by The Nature Conservancy. As part of the effort, River Partners will be planting vegetation totaling 193,000 trees, shrubs, native grasses and vines onto the river’s floodplain. The plantings will have a scientificbasis, designed to attract specific wildlife and arranged in a manner to buffer or dissipate wind wave action that can cause levee erosion. With the levees moved back, at one point over a mile from the river, floodwaters will have plenty of space to spread out over the broad floodplain.

One last and contemporary thought: restored f loodplains that allow floodwaters to flow over a wider area without causing damage, provide dam operators with more flexibility in timing the release of lake waters. The operators of the Oroville Dam, for instance, can take advantage of the greater flood capacity of the Feather River thanks to restored floodplains downriver, especially the major setback levee and riparian restoration project carried out at the confluence of the Feather and Bear Rivers.

The bottom line: Protecting and restoring the natural and beneficial functions of floodplains will not only reduce flood damages, but also contribute to a community’s safety, economy and environmental well- being. Longtime Chico resident Irv Schiffman, 78, is a retired Chico State University professor of political science and chairs the board of River Partners.