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Home » News/Events » The Journal » Vol. 13 Issue 1 » Putting the Flood Back on Floodplains

Putting the Flood Back on Floodplains
(with a little help from El Niño)

  • By Michael Cook, Northern California Regional Director

(Above) Flooded Sacramento River at River Road, west of Chico (1/18/2016).

To attempt to calm the apocalyptic terror created by the fourth year of the worst drought in California history, those “in-the-know” focused our attention on the past, highlighting the fact that some of California’s driest periods ever recorded were also quenched with some of the wettest. As one farmer put it: “we’ve had more floods in the Central Valley than we’ve had droughts”. Finally, this water year is shaping up to deliver us from drought as the major deluges of 1983 and 1997 did.

Industry and politicians are calling for more water storage in the form of reservoirs, while the governor has set strict targets for state-wide water conservation. We need to use water more efficiently and capture this El Niño’s floodwater for future use. With rising global temperatures, our natural water storage in the snowpack of the Sierra Nevada is shrinking. With the construction of the nation’s largest water delivery system (the Central Valley Project and the California Aqueduct), our natural water storage in the below-ground aquifers of the Central Valley is collapsing. But perhaps there is a smarter way to buffer California’s drought-flood cycle than building more dams and diverting more streams. And perhaps we can simultaneously improve public safety from flooding, and recreate some of our lost ecological capital, while supporting our growing economy and way of life: by restoring flooding back to floodplains.

(Above) River Partners’ Bear River Setback Levee Project alleviates flooding on both the Feather and Bear Rivers while also creating habitat for fish and wildlife. (Photo taken March 2011.)

As we entered the summer of 2015, with the coronation of the current drought as the worst ever, everyone’s attention was focused on what little water we had and who should have the right to use it. Water allocations to major irrigation districts across the state were hammered, causing acreage of farmland to lie fallow or worse – expensive orchards to be ripped out. Our reservoirs drained to historic lows. The economic effect of lack of irrigation water for agriculture was estimated in the billions. And we turned to any means necessary to keep the farm fields in production. For large areas of the Central Valley that meant devastating increases in groundwater pumping which exacerbates an already massive problem: land subsidence in the San Joaquin Valley. The USGS calls the observed earth sinking driven by groundwater overdraft in California “one of the single largest alterations of the land surface attributed to humankind.” This groundwater pumping is even more alarming because once the water is removed from below the earth’s surface, it cannot be replenished. The subsidence is so severe that we are starting to see sinking and cracking of sections of the California Aqueduct.

It wasn’t until scientists took notice of increasing ocean temperatures building momentum in the middle of the Pacific that we became less focused on the drought and more on the promising potential of the upcoming winter being influenced by El Niño. The El Niño effect (large-scale climate interaction between ocean and atmosphere, connected to a periodic warming in sea surface temperatures across the central and east-central Equatorial Pacific Ocean influences weather patterns for North America bringing wetter-than-average winters to California) is named after the Spanish word for The Little Boy or Christ Child based on the time of year in which it normally occurs – some Christmas present!

(Above) A rising Sacramento River flooded River Partners’ Willow Bend Preserve in January 2016. Recently, spring-run Chinook salmon were documented in this restored floodplain habitat.

After months of monitoring and analysis by the National Oceanic and Atmospheric Administration (NOAA), we believe the current El Niño could potentially match or rival that of 1997, the strongest El Niño on record and by which all others are measured. Past El Niño cycles have been responsible for billions of dollars in flood damages across California, and with our aging flood infrastructure, what looks like good news for thirsty California is also a public safety nightmare. In fact, experts studying this El Niño have indicated that the storms resulting from this current weather phenomenon could be so severe and destructive, that it’s aptly been named the Godzilla El Niño. In the first ten days of the new year, southern California was hit with a torrential storm and high-intensity rainfall, overwhelming storm drains, causing hillsides to give way, with the quintessential urban stream, the Los Angeles River, roaring back to life. Although the flow only peaked at about a third of its capacity, it brought attention to the river that many Angelinos had all but forgotten. Less than two weeks later, a series of storms hit northern California one after another, bringing several inches of rain to the foothills and feet of snow to the Sierra Nevada. After a 72-hour period, a weather station located at the base of Shasta Dam had measured 7.56 inches of rain. The following day, six of the twelve stage and flow gages on the Sacramento River were near flood levels. One of these gages, located at the Tehama Bridge, crested at 212.8 feet, a mere 2½ inches below the level where the river’s considered flooding. Further downstream, two of the river’s flood control weirs were overtopped, spilling into the Sutter Bypass like it is designed to do.

Although these storms did not cause any major damage, they provided a quick reminder just how fast things can turn from bad to worse. Fortunately, the work that River Partners has been conducting for the past 17 years uses a multi-objective approach to address flood control and public safety, while creating habitat for fish and wildlife species at the same time. Through the restoration of natural river processes, we are helping ensure reliable water resources during dry years and assisting in flood control during the wet ones.

Many fingers have been pointed at Central Valley agriculture during this drought, accusing farmers of cultivating lucrative crops in an historic desert, the ultimate example of water waste for individual gain. While it is true that agriculture accounts for a large percentage of California’s water use, the Central Valley has never been a desert. Before the gold rush, the Central Valley resembled more of a swamp, not a desert, for a good part of the year. Before dams and levees altered the natural hydrology of the State, winter rains and spring snowmelt would pour out of the mountains, overwhelming the rivers and tributaries on the valley floor, causing them to overtop their banks and spill onto their floodplains on a regular basis. This water would remain there, creating a complex system of wetlands and riparian habitat that would cover much of the valley well into summer. This water would percolate into the aquifer providing prolonged water supply for native trees and shrubs.

The wetlands and forests provided stopover habitat for waterfowl to rest and forage for food as they migrated up and down the Pacific Flyway. Inundated floodplains provided ideal conditions for rearing juvenile salmon and steelhead. As the water spread out, it slowed down and warmed up, creating a smorgasbord of zooplankton and other aquatic invertebrates for the young fish to feast on for months. Their increased size allowed them to swim faster and avoid predators, giving them a much greater chance of reaching the Golden Gate on their journey out to sea

Just as it is for fish and wildlife, reconnecting our rivers back to their floodplains is also critical for water supply and flood control. When our rivers are given more room to spread out, they will put less pressure on our aging levees and flood control structures, especially during future unpredictable storms that may be influenced by El Niño and our changing climate. When our rivers are given more room to spread out, they are also able to provide the crucial function of groundwater recharge. By recreating multibenefit floodplains, we can allow rivers to flood where we need them to, thus protecting the folks downstream from flood damages and stocking water away in aquifers and surface storage for use during the inevitable lean times. As John Muir put it in 1869 “when we try to pick out anything by itself, we find it hitched to everything else.”