* Editor’s note: This is the first in a three-part series of articles by the Putah Creek Council to educate residents about a creek restoration project to improve water quality and wildlife habitat in and along Putah Creek.
By Libby Earthman
During the 1950s old car bodies were commonly embedded along river banks by self-reliant farmers who needed to control severe erosion, a method called “Detroit riprap.” This method was employed by some along Putah Creek, including Ethel Hoskins’ family, who owned much of Pleasants Creek.
The use of Detriot riprap was sufficiently widespread that in the late 1990s when one of Ethel’s friends visited, he looked at the banks of Pleasants Creek and joked about all the car bodies: “Wow, Ethel. That must have been quite a car wreck.”
Erosion is a natural process that moves soil and rock downhill and downstream, and is an important force in shaping rivers. It is possible to have too much of a good thing: Human activities occasionally speed up this process enough that erosion can threaten property and impact water quality.
Hoskins set out to find a permanent solution to the erosion problem in 2002. With funding from a variety of local, state and federal agencies, her ranch became a demonstration site for working with natural materials, including rocks and native vegetation to help undo prior damage and prevent further degradation.
John Knowles, ranch manager, was eager to join in the conversation about the 2002 creek project that stabilized the creek and brought back much of the wildlife that enriches the area.
“It’s a different creek today than it was before the project,” he says. “When you go down there today, it’s peaceful. It’s beautiful. For a while, you are someplace else.”
As a lifelong resident of Pleasants Creek, a tributary to Putah Creek, Hoskins likes to laugh about the fact that she is the granddaughter of the original 1850 homesteader on the creek: William James Pleasant. Hoskins has her grandfather’s daily journals, dating back to the mid-1800s. He wrote of hunting bear, elk and antelope on the property, and catching steelhead upstream of the homestead on a tiny tributary to Pleasants Creek.
“How many elk, bear, antelope roamed this area? We will never know,” Knowles said. “We do have one heck of a creek now, even if it’s not entirely what it once was. We have mink, otters, beaver and bluebirds. We have documented 119 species of birds on the property.”
The changes present at the ranch today are a result of concerted effort to reduce erosion using native plants and natural materials, control invasive weeds and welcome wildlife back to a portion of its former range. In moderation, erosion is not a problem, it is even beneficial. Erosion is a natural process that brings new gravel, cobble and soil into a creek, replenishing what washed downstream in earlier storms.
The troublesome erosion in Pleasants Creek began in the 1950s, soon after the completion of Monticello Dam and Lake Berryessa. Few anticipated one of the largest unintended consequences of dams: They often cause massive erosion in downstream tributaries. For more information on the mechanics of this process, visit www.putahcreekcouncil.org/news.
Hoskins remembers Pleasants Creek as a moderate dip in the landscape, perhaps 15 feet deep and 30 feet wide. The accelerated erosion since the completion of Monticello Dam dug the channel up to 40 feet deep and 100 feet wide, with sheer cliff walls void of any vegetation. Native plants — plants that evolved in the region and provide erosion control and wildlife habitat — could not survive on the resulting sheer walls of Pleasants Creek.
The residents along Pleasants Creek, shocked at the sudden change, began arming banks with Detroit riprap and the California Conservation Corps came in to plant a “miracle” plant: arundo. Arundo is a false bamboo that was then believed to be a silver bullet for halting erosion — it grew quickly, spread rapidly and needed no additional water or maintenance.
Like many invasive weeds, arundo displaces native plants that provide wildlife habitat. And while arundo grows quickly, it does not prevent erosion — it accelerates it. The tough, upright stalks impede flow, slow water velocity and cause fine sediment to accumulate among the plants. In areas where arundo is thick, it is common for the water to carve a new channel around the arundo rather than pass through it, making the erosion problem even worse.
Putah Creek is dammed twice before it reaches Winters: once at Monticello Dam to create Lake Berryessa, and again less than 10 miles downstream at the Putah Diversion Dam to create Lake Solano. Pleasants Creek joins Putah Creek just upstream of the Putah Diversion Dam, so the massive sediment it carries downstream during storms is delivered to Lake Solano — the diversion point for water heading south to Solano County for drinking water and agriculture.
Such massive amounts of sediment being dumped into the diversion point for a significant portion of the drinking water for Solano County makes treating the water to drinking water standards very complicated. This problem can be very expensive to address.
See next week’s article, “Study Identifies Erosion as Threat to Local Water Supply,” to learn about how erosion and sediment impact an important drinking water source for Solano County.
For more information about this project, visit http://tinyurl.com/solanowater.
— Libby Earthman is executive director of the Putah Creek Council.