A message from 10,000 cfs
In the early morning hours of Friday, Nov. 30, between 5:30 and 5:45 a.m., the volume of water roaring like a freight train down the bed of Sonoma Creek, topped out at 10,600 cubic feet per second.
That figure may not mean much if you’re unfamiliar with cfs stream flow volumes, so let’s put it in context. During the dry summer months, that same creek bed carries maybe 1 to 3 cfs. At 600 cfs it is a quite juicy whitewater run.
For whitewater paddlers, 10,000 cfs on the Tuolumne, Merced, Stanislaus, American, Yuba or Feather rivers would be a heart-stopping, experts-only Class V flow.
That much water between the constricted banks of Sonoma Creek is massive. Richard Dale, executive director of the Sonoma Ecology Center, made a quick computation for the 24 hours between midnight and midnight on the 30th and calculated that close to 2 billion gallons of water slid past the stream gage at Agua Caliente.
That is sobering food for thought and here’s why. A century ago, before widespread irrigated agriculture, several thousand acres of grapes and grids of subdivisions sprang up in the Sonoma Valley, the ability of our local watershed to hold, absorb and slow the flow of rainwater was exponentially greater.
In many places, the bed of Sonoma Creek was both wider and shallower, containing extensive ponds navigable by rowboat as well as shaded pools where juvenile salmon and steelhead could grow to adolescence before braving the open bay and the vast ocean downstream.
Human intrusion reduced the width of the riparian corridor as trees and brush were cut back to make way for crops, while increased suburban and urban infrastructure channeled runoff ever faster over asphalt and concrete into a stream bed with less arboreal buffer to slow down the flow.
Simultaneously, the groundwater tables began to be pumped ever more aggressively to nurture the expanding orchards and vineyards and domestic demands.
Eventually, water ran faster when it rained, and creeks ran drier when it didn’t, because the dropping water table drained the subsurface flow of the creeks. During storm events, stream beds were scoured and cut deeper between their banks, further limiting the nurturing nursery capacity of the arterial system.
And now, when you see 10,000 cfs steamrolling through the Valley, what you’re witnessing is a loss of topsoil scoured from the naked land, a loss of habitat as the deeply-incised and narrowing streambed accelerates the force and volume of water rushing through it, and in some places a reduction of groundwater because the naked, cultivated landscape can’t retain enough water to replenish aquifers drawn down in summer droughts.
How this hydrologic drama will continue to evolve in the full blossom of climate change isn’t entirely clear but the potential and probable consequences aren’t particularly pretty.
That said, the Sonoma Ecology Center, along with several other restoration partners, is years into an array of projects aimed at slowing and reversing the effects of human intervention in the watershed. Their projects include the Nathanson Creek Preserve, Fryer Creek and Sonoma Creek flood mitigation and habitat enhancement and many more.
Unless we continue that kind of response, 10,000 cfs may become a common sight.