The major work of excavating the wetland and planting the salt marsh at the NCOS Restoration Project is complete, but understanding how the watershed impacts the wetland and its many functions is an ongoing, long term focus of CCBER and UCSB faculty and students. The health of a wetland like Devereux Slough is inextricably linked to the health of the watershed that drains into it, and this can be impacted by inputs such as trash, excess nutrients, and sediment that ride into the wetland on stormwater runoff.
An artist's representation of the watershed of Devereux Slough.
Much of the trash that finds its way into the streams and tributaries of the Devereux Slough watershed is eventually flushed down into the wetland during storms. Before the restoration of NCOS, this trash was mostly hidden within the choked channels and vegetation of the Ocean Meadows golf course. Now it will be clearly on display on the banks and shores of the restored estuary. The primary sources of trash entering the system are Phelps Creek and the storm drains from the residential areas between the Camino Real mall and NCOS. That trash is primarily a mix of fast food and convenience store packaging, along with some larger debris that might be left in creeks by transients. CCBER, Channel Keeper, the Environmental Defense Center and other groups lead efforts to remove trash from creeks, storm drains and the wetland, but this is labor intensive and mucky work. Keeping trash from getting into the creeks and storm drains in the first place is smarter and safer, and better for wildlife, plants and the aesthetics of the landscape.
CCBER staff and volunteers have removed loads of trash and large debris from NCOS creeks and the wetland several times.
Through a Central Coast Regional Water Quality Control Board regulation called the “Trash Amendment”, the City of Goleta is now required to reduce trash in urban run-off. CCBER has been working with the City to help make the Devereux wetland a priority, and recommends that the city initially install nets to catch trash at the southern end of the Phelps Creek concrete channel where it passes under Phelps Road (similar to the image below, though not as large). According to Councilmember Kyle Richards and the Public Works director, this is a priority, but with many steps involved, from securing funding approval to environmental review, implementation of these fixes may take some time. For now, we will continue our efforts to remove trash from the wetland, creeks and storm drains, and we ask you to please help keep an eye out and pick up loose trash while walking on the trails or in your neighborhood.
An example of a system of nets for capturing trash in creeks and storm drain channels.
Studies of urban watersheds have shown that "urban drool" from sources such as over-irrigated lawns and upstream golf courses can add excess nutrients such as nitrogen, phosphate and ammonium into wetlands. These can spur the growth of algae, reduce the diversity of aquatic fauna, and lower water quality overall. Wetlands, by their very nature, support natural nutrient cycling bacteria and plants that uptake nutrients and filter sediment. The design of NCOS integrates freshwater wetlands where each of the four main tributaries enter the estuary, and these should help the system perform these natural functions. CCBER is assessing these inputs and their effects on wetland functions through a number of studies.
A stormwater sample collection system recently installed on a tributary that drains into NCOS and Devereux Slough.
The first is a program for collecting incoming and outgoing stormwater and analyzing nutrient content in those samples. Stormwater samples have been collected by hand over the last couple years, and recently installed "auto-samplers" will collect multiple samples over the course of a storm, providing more detailed data. These systems are being installed at the Phelps Creek and Whitter stormdrain channel inputs, and at the Venoco Road bridge where the restored upper wetland connects with the lower slough. In addition, the impact of nutrient inputs on measures of water quality such as dissolved oxygen are being monitored with weekly hand measurements at four locations in NCOS, and continuously in the lower Devereux Slough where a sensor records water quality parameters every 15 minutes. These measurements are then integrated and analyzed with data from monthly sampling of aquatic invertebrates in the restoration project and the lower slough that is being conducted by students with mentorship from UCSB professors and the Santa Barbara Audubon Society.
UCSB Students collecting water quality data and aquatic arthropod samples in NCOS wetlands.
Excess sediment, such as in debris flows or large erosion events, can be a serious problem, as many of us have experienced. The more chronic problem in the estuaries below many urban watersheds is actually insufficient sediment inputs from paved-over watersheds. The lack of sediment input limits the ability of the wetland to accrete sediment and for the plants to respond to the pressures of sea level rise, which can cause the wetland to drown or become un-vegetated. CCBER is monitoring sediment inputs with the newly installed auto-samplers to both document whether the project itself generates sediment from erosion, and to understand the sediment inputs from the watershed. The translation of sediment inputs to salt marsh growth, or accretion, will be measured using 50 feldspar plots established around the restored wetland and lower slough, where we will be able to measure actual accumulated sediment in the wetland. Hand collected "grab samples" of stormwater inputs and outputs from the two storm events in the winter of 2018 showed that Devereux Creek was the only significant sediment source.
Examples of feldspar plots for monitoring sediment accretion in Devereux Slough.
These various lines of inquiry will hopefully improve our understanding of how the restored wetland functions, and also provide evidence through data that encourages the City of Goleta and the community to prioritize the reduction of trash and other pollutants in the watershed. The removal of Ocean Meadows Golf Course has already enhanced water quality in the lower slough by reducing nutrient inputs from the irrigation of the golf course with nutrient-rich reclaimed water. We will continue to provide updates on studies and monitoring of the wetland through newsletters and other media. And you can always contact us by email (email@example.com) or through our contacts page for more information or if you would like to get involved.