By Paul Belz
“A creek has two jobs,” Christopher Richard told a group of adventurous hikers in the Sausal Creek watershed. “One is to transport water, and the other is to transport sediment.” Christopher was the Editor, Publisher, Webmaster, and Biologist for the series of San Francisco Bay Area Creek & Watershed maps published by the Oakland Museum of California, and was there with our group to trek around the watershed and examine the health of the Creek and of the surrounding forests.
Ecologists use the term “watershed” to describe an area in which all the water flows off the land, into creeks and ultimately to one location, such as a creek entering the bay. The watershed includes lakes, streams, tributaries, and the surrounding land. Each watershed is a unique system with various habitats corresponding to geology, microclimate, and patterns of development. Each has a particular group of plants and animals. In the Sausal Creek watershed, the more natural tributary, Palo Seco Creek, emerges from a redwood forest and joins Shepard Canyon Creek to form Sausal Creek. This larger stream then flows through, a bay/oak ecosystem, a dogwood corridor, adds charm to backyards, disappears into a culvert, and eventually drains into the San Francisco Bay near the Fruitvale Bridge.
The hike took us to a stream where we found remnants of culverts the Works Project Administration (WPA) built in the 1930s to channel and direct the stream course. Christopher described how a stream course functions as a kind of conveyor belt with three zones. The zone of erosion is the steep upper area where the stream picks up sand, stones, and even boulders. The stream meanders through the second, flatter zone of transport, depositing some sediment on one bank and eroding the opposite side. The third zone is the area of deposition where the stream merges with a larger water body, slows, and drops its remaining load as a sand bar or delta. Sausal Creek does this when it hits San Francisco Bay.
“A healthy stream system needs to be eroding, at a moderate pace, throughout its headwaters,” Christopher said. “If you come in here and pour concrete over everything, it will starve the lower areas of the sand and gravel. Critters need that sand and gravel for habitat, and fish need that habitat to lay their eggs.” In line with a zealous mandate to stop erosion, the WPA concreted reaches of Sausal Creek in the 1930s. When a hiker asked Christopher why the agency did this, he shrugged and said, “Some of it was hubris, the idea that a human controlled natural situation is a better situation.” Today, these hardened creek beds are collapsing and being removed to restore the creek to more natural function.
Hiking through rugged wooded ridges along a path that was partly dirt and partly cracked asphalt, Christopher mentioned that the logging companies once hauled redwood logs with oxen along the road that once lay here. Today, upper parts of this area are covered with second growth redwoods. Native redwood sorrel, a small plant with heart-shaped leaflets, covers the ground along with Bermuda buttercup, a similar-looking but invasive non-native plant.
We found many other native plants among the redwoods. One hiker called thimbleberry, with its huge leaves, “nature’s toilet paper”. Fuzzy-leaved hazelnuts thrived in sunny trailside spots; Christopher mentioned that some native Californians may have eaten them more often than acorns. Downstream, coast live oaks and bay laurels replaced redwoods in a drier part of the woodland. California buckeyes, Indian soap root, and honeysuckle also thrived, but introduced English ivy and Scotch broom dominated some hillsides.
In some areas next to the trail, loose soil testified to the hikers and off-leash dogs who had cut across habitat between switchbacks, contributing to unwanted erosion. “Erosion is a Goldilocks issue, because there’s a ‘just right’ amount,” Christopher said. “Too much can mess things up, but not enough is also bad.” We scrambled along the Sausal Creek stream bed, climbing over boulders and broken slabs of WPA concrete structures. “Think of the Dust Bowl – the whole country was mobilized to control erosion,” he said. Urban graffiti and plaques stating “WPA 1938” covered some of these structures. Still, a healthy forest surrounded this area. We found a damselfly that had just emerged from its larval stage in the water and was preparing to fly from a flat rock.
Native creek dogwoods, willows, bay laurel, cow parsnips, and horsetails thrive in an area where Friends of Sausal Creek has worked with the city of Oakland to restore the natural stream corridor. Here, concrete slabs are very scarce, and the Creek tumbles over mossy boulders. Robins and other songbirds called to us as we hiked. We passed one pond where native trout have made their home. Christopher praised Friends of Sausal Creek as a heroic group that has worked hard to help native plants return to this place. “Yeah, the ivy keeps coming back, but in the stream, they’ve created a good foothold for native vegetation,” he said.
Following Sausal Creek into Diamond Park in Oakland’s Fruitvale District, we ended our hike by passing a swimming pool, picnics and a birthday party. The creek enters an underground tunnel here that takes it towards its destination in the San Francisco Bay. Friends of Sausal Creek currently works hard to restore the natural stream course through the Park; this group faces huge challenges, but it has begun to heal this watershed.