Topanga Environmental Workshops

On March 25, The Topanga Creek Watershed Committee is launching a new program, a series of workshops designed to provide education about Topanga Canyon’s natural environment. Everyone is invited to attend, and anyone who has information to share is welcome to direct a workshop of their own.

I will kick off the program with a tour of my Geology Masters Thesis project area. I’m studying three landslides along Topanga Creek and their influences on aquatic habitats, focusing on habitat conditions for steelhead trout. The project will investigate how the landslides affect pools, gravel beds, instream cover, water turbidity, sedimentation and canopy. Landslides typically cause damage to habitat by delivering excess amounts of sediment into the stream channel that buries spawning gravel and fills pools, but they might also have positive effects.

Past research on landslides has focused mainly on negative environmental effects, but my project will document both positive and negative effects from these specific landslides. Potential positive effects include creating boulder-scour pools and dam-pools that provide instream cover and act as sediment traps, and delivering gravel to the stream that provides spawning habitat.

This first event will be held on Saturday, March 25 from 10 a.m. to noon. We will meet at the site where the “Green House” was removed from the stream bank along Topanga Canyon Boulevard, approximately 1.5 miles upstream from the coast.

On a topo map, the wide spaces between contour lines on the slope just west of the site represent a large mid-slope bench. This bench was created by a deep-seated landslide that occurred around a thousand years ago, when a large section of the mountain slumped downslope. The toe of that ancient slide has been undercut by stream erosion. The landslides we see along the stream are sections of this old landslide deposit that are de-stabilized by stream undercutting.

Much of the tour will take place along the roadside where terrain is gentle and access is easy. We will spend some time across the creek on the slide deposit. If you want to cross the creek with us, be prepared to negotiate rough terrain and expect to get wet and muddy. I will present lots of information about landslides that have had a major role in producing Topanga’s topography. Because of traffic hazards along the road, the rough terrain, and other potential dangers, this tour is not suitable for children. If you have kids interested in this kind of thing, you can take the information you gain here and share it with them in a safer environment.

People have expressed interest in conducting other events on subjects including Topanga’s wild mushrooms and local soil erosion problems. I’m hoping someone would also like to lead a bird-watching event and a tour of Topanga’s native plants. If you would like to conduct a tour on these or any other subject, let me know and we’ll schedule a time for you. Call me at 310-453-8504, or email me at mhorns_1@hotmail.com.

I believe this program is a good way for us TCWC folks to get to know our watershed better and to get our community more aware of Topanga’s natural wonders. All help and support will be appreciated.