WINDOW ON CLEAR LAKE
Part 4- Fixing the Clear Lake Uplands
By Jim Steele
The upland terrestrial ecosystem boundary is defined as the 450-square-mile watershed area that collects rainfall feeding Clear Lake. Within this ecosystem are the mountains and soils, with streams draining, flooding, and shaping the landform. Competing for space and nutrients are the many plant and animal species common to the inner coastal range of California. Some of these species have disappeared since the arrival of western settlers, and some have been introduced from other ecosystems. Historically, annual flooding and receding waters replenish the plants with new soil and recharge the groundwater. The meandering channels in the lower elevations run into wetlands that capture any remaining sediments before the water enters the lake. Wildlife abounded in these slow-moving waters, seeking their lowest level.
When western settlers saw the few areas that didn’t flood annually, this drier area was increased by adding levees to bypass wetlands and straighten streams for agriculture and housing. Removing the stream meander meant the water would flow off the land faster, reducing flooding. But it also reduced the population of the floodplain-adapted minnow common in this environment. The threatened “Clear Lake Hitch” was listed in 2023 under the California Endangered Species Act because of habitat alteration.
Bypassing the wetlands resulted in the removal of the sediment-settling area and also reduced wetland wildlife populations. As sediment-laden water entered the lake, cyanobacteria scum blooms became more common because they are very competitive in nutrient-rich, low-oxygen environments. The new thinking is to restore the wetlands and regain their water-filtering powers.
However, restoring wetlands is expensive and requires millions of dollars for planning, land acquisition, and reshaping the landform. It’s quite an investment and a good goal, so unless the incoming sediments from land-use disturbance are significantly reduced, any expensively renewed wetland will quickly fill in. Looking upslope should be a priority step in reducing sedimentation to both the lake and restored wetlands.
What are the offending upland sediment producers? Arguments with finger-pointing and no self-admission of blame have been common. Agriculture in all its forms is the usual suspect, but poor road construction, drainage, and slope disturbance are more likely. Leading the slope disturbance category is Off-Road Vehicle [ORV] use. In Lake County, many areas of the hillsides are made accessible to ORV’s by roads established by failed subdivision projects and are uncontrolled. Adding to this are many ORV activity-permitted areas within US Forest Service lands in the watershed. But the largest ORV park, with thousands of annual use days, is on BLM land adjoining Scotts Creek. The pathway for this erosion is directly to the lake, bypassing the Middle Creek seasonal wetland complex. Restoring the wetland and removing the bypass levees without fixing this upland sedimentation problem will result in reducing the wetland’s filtering capacity after only a few years.
Several things can reduce the upland sediment input. The USFS and BLM Agencies have other public lands that do not drain to the lake, and moving the ground-disturbing activities to areas outside the watershed boundary is the best approach. After that, the large surface area of the BLM ORV Park would require land stabilization and replanting. The area along Scotts Creek would also benefit from bank stabilization structures. Scotts Creek now has braided water channels indicating a large amount of erosion moving through the system. Passing this sediment slowly downstream using check dams will reduce the impact on downstream areas such as Scotts Valley, where nearby housing is vulnerable to flooding. Picking the right standards of repair will be important. Scotts Valley used to be a meandering valley subject to annual flooding, and housing requires changes compatible with protections.
Of course, all of the sediment-producing activities within the Clear Lake basin should be mitigated. But the largest low-hanging fruit, consistent with recommendations from decades of studies on the lake, is found in the Scotts Creek drainage and the Middle Creek wetland. It should be noted, however, that none of the past studies measured large-storm impacts, such as the 1955 or 1964 atmospheric storms that occurred in the Eel River basin. It is these potential storm levels that should serve as the benchmark for the sediment mitigation measures in the Clear Lake Watershed. Fixing Clear Lake depends on a community of agencies, tribes, and the public recognizing, monitoring, and repairing problems across all three ecosystems to meet proper standards and protect the future. With a new three-ecosystem understanding, Clear Lake can be restored and made clear again.
