The southern Sierra Nevada is covered in the thickest snowpack in recorded history, and the rest of the range is not far behind. When all this snow melts, where will it go?
You can read the answer in the Central Valley landscape. At first glance, it’s almost flat, covered in layers of gravel, silt, and clay washed down from the mountains over the eons by rain and melting snow. In the middle of the flatness are gradual slopes down to the center of the valley, where the Sacramento River creates a watery vein to the north and the San Joaquin River does the same in the middle. Once – before the late 19th century, when newcomers began draining land and channeling water from wetlands to agricultural fields – the southern part of the valley was home to the largest freshwater lake, by area, west of the Mississippi.
Many small California valleys also feature rivers, including the Salinas, which are often nearly dry but flood their banks in wet years like this from torrential rains rather than snowmelt.
This is where the water goes: to the bottom of the valleys, swelling the rivers in flood years until they overflow, putting communities like Pajaro and their inhabitants at risk.
During the Great Flood of 1861-1862, water covered the entire Central Valley. It would have been possible to sail from what was not yet Bakersfield, north past the flooded Capitol in Sacramento, almost to where Redding now stands.
In drier times, however, these same flat floodplains seemed particularly attractive to farmers and builders, so now the valley bottoms are cultivated and developed. But in wet years like this, all that rain, along with the sleet, always needs a place to go, and it pays no attention to human development. He is always looking for the lowest ground, and he will find it. A quick glance at a satellite photo of the snow-capped Sierra makes it clear: No number of dams can hold all this water, no number of reservoirs can hold it.
The solution is shockingly simple, relatively inexpensive – compared to the cost of cataclysmic floods – and surprisingly uncontroversial. We just haven’t done it on the scale yet.
California needs to restore its floodplains. Not all valley bottoms, and not as they were in pre-development times. But he must have many more acres of land set aside for flood waters.
Restoring floodplains requires setting aside low interior areas for water to accumulate away from homes and critical infrastructure. It’s as simple as moving dikes. Instead of building them higher and higher, to drive water out to sea, levees set back from the banks give water a place to slow down, settle and seep into the ground, safely , away from human habitation and commercial investment.
There are multiple benefits. The first is, of course, the protection of life and property, as floodwaters have a gathering place other than city streets. Beyond that, water that settles on floodplains infiltrates the ground and, where geology permits, recharges groundwater dangerously depleted by agricultural overpumping.
And floodplain restoration restores seasonal wetlands, which is good for the entire natural network that holds California together — including native plants that are less likely to burn during fire season than invasive species. fish that return to their spawning habitat, migratory birds that find nesting areas, mammals that can migrate again through the valley.
During dry seasons, restored floodplains can be wildlife sanctuaries. But they can also be football fields, golf courses, or even agricultural fields for annual crops such as tomatoes or melons. But not houses or perennial crops like almonds.
Some homes are already where floodwaters are naturally likely to accumulate, which poses a dilemma. Should we protect them from the floods at all costs or abandon them there? The questions are the same as for homes destroyed by wildfire and whether it is society’s duty to protect people who choose to rebuild in an area at risk of fire, flooding or other disasters. predictable. There is no consensus. As with coastal neighborhoods threatened by rising sea levels, in some cases the prudent and cost-effective move will be a managed retreat from riverbeds that could flood, even if they are dry in most years.
All that is missing in floodplain restoration is the will and enough money to buy land, usually farmland that has become too expensive to keep under cultivation. Governor Gavin Newsom is touting his decision to use some of this year’s overabundant rains to recharge groundwater. But it also cut most floodplain restoration funds from its proposed budget for the third straight year.
In years like this, when the state seems to have more water than money, a floodplain restoration advocate’s thoughts may turn to the ballot. A well-designed bond measure could give a serious boost to needed restoration efforts. Even though flooding threatens the state today, a bond could easily land on the ballot in a parched year when atmospheric rivers, historic snowpacks and submerged highways are long forgotten. But whether it’s a budget allocation or an obligation, let’s try to remember: there will be even wetter winters, and restored floodplains can protect homes and capture water for use during very dry summers.