SAVING a RARE PLANT in an URBAN ENVIRONMENT by Keith Greer and Holly Cheong
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A-Jacks, erosion control devices in Lopez Canyon, San Diego County, used to check water flow and thus protect the habitat of the rare willowy monardella. All images used courtesy of City of San Diego, 2003. SAVING A RARE PLANT IN AN URBAN ENVIRONMENT by Keith Greer and Holly Cheong or its size, San Diego County is gered willowy monardella (Monardella been covered by impervious surfaces Fblessed with one of highest num- linoides Gray ssp. viminea (E. Greene) such as pavement or structures. ber of endemic species in the Abrams; see sidebars) from changes in When urbanization spreads into un- nation. Considered a hotspot for en- urban hydrology. developed watersheds, the percentage dangered species (Dobson et al. 1997), Willowy monardella occurs in the of impervious land surface increases, San Diego has also undergone waves alluvial terraces and cobble bed of in- resulting in changes to hydrology that of rapid urbanization since the 1950s. termittent streams in Lopez Canyon, include increased stream discharge and While recent conservation efforts a part of the Los Peñasquitos Preserve velocity due to urban runoff, as well as have focused on protecting species located within south and central San changes in the timing of these flows. and their habitats from direct impacts Diego County. While Lopez Canyon White and Greer (2002) documented such as urban development, active is part of a city park managed for its an annual 4% increase in stream dis- land management is equally important natural and cultural resources, indirect charge since 1972 due to watershed to protect species on lands already impacts from watershed urbanization urbanization in nearby Los Peñas- preserved. have threatened the existing monar- quitos Creek. This increased discharge This paper describes efforts of the della population. Since the mid-1970s and velocity has resulted in increased City of San Diego, in conjunction with the 4.5 square mile watershed of Lopez scouring of the streambed, undercut- the nonprofit Friends of Los Peñas- Canyon has been developed into the ting the alluvial terraces in Lopez Can- quitos Canyon, to protect a popula- suburban community of Mira Mesa. yon that support willowy monardella. tion of the federal and state endan- Currently, 65% of the watershed has The loss of alluvial terraces and the 18 FREMONTIA VOLUME 33:1, JANUARY 2005 enlargement of the intermittent stream ceived grant funding from the Califor- (RWQCB) would be very time-con- channel were predicted by Karen nia Department of Fish and Game and suming for the berm design. In addi- Prestegaard (1979) in her masters the- the California Coastal Conservancy to tion, grant funding would have expired sis. Current and pre-urbanization aerial implement an erosion control project before the permitting process for photographs support Prestegaard’s pre- to protect willowy monardella in those agencies could be completed. dictions, and can be seen in Figure 1. Lopez Canyon. The first task was to Also, the berm design could have pos- Since 1995 the Friends of Peñasquitos design the project. Several alternatives sibly impacted an already eroded sewer Canyon have documented the loss of were investigated and rejected prior to line within the canyon. Instead of risk- several large patches of monardella af- settling on the final design. ing unforeseen negative impacts to the ter large storm events. Effective man- The first alternative came from two canyon, the project team decided to agement for willowy monardella in California State Parks engineers who look for another solution. Lopez Canyon requires managing the volunteered their time to survey the After consulting with staff from changes in hydrology caused by water- monardella sites in Lopez Canyon, many agencies, it was determined that shed urbanization. along with a volunteer representing a new form of erosion control, called Recognizing this problem, staff from the Friends of Los Peñasquitos Can- A-Jacks, would be the best solution for the City of San Diego and volunteers yon Preserve. They proposed a series Lopez Canyon. A-Jacks are concrete from the Friends of Peñasquitos de- of grade control structures including armor units designed to interlock into termined that there was a need for hy- drop structures, weirs, gabions, and a flexible, water-permeable chain. A- drologic structures to slow the water bank armoring. Ultimately this pro- Jacks help dissipate water velocity, velocity and reduce scour. In addition, posal was deemed infeasible because protecting channel terraces from they determined that it would also be its cost exceeded the available funds. scouring and erosion, two problems necessary to address changes in hydro- The second alternative came from experts knew they had to solve. A- logic condition in the entire watershed. the Natural Resources Conservation Jacks also collect sediment within the This resulted in a two-phase approach: Service (NRCS) of the USDA. Their water, minimizing impacts down- a long-term goal to address the hydro- engineers drafted plans for a simpler stream from deposition, a third prob- logic changes and a short-term goal of design involving cobble berms to pro- lem in the Canyon’s waterways. protecting the existing patches of wil- tect the two major monardella sites Downstream deposition of sediment lowy monardella. from erosive wintertime flows. These into Los Peñasquitos Lagoon had al- Working with a diverse citizens ad- plans were reviewed in a preliminary ready caused significant impairment visory committee, the Cities of Poway, meeting with the federal and state re- (California State Coastal Conservancy Del Mar, and San Diego began look- source agencies in 2002. The US 1985). Collection of sediment would ing at a comprehensive, long-term ap- Army Corps of Engineers (ACOE) also help stabilize the terraces, pro- proach that would create a watershed argued that the berm for the down- vide additional habitat areas for wil- management plan for the area. Those stream site would redirect a second- lowy monardella, and hide the A-Jacks involved have just started to identify ary channel flow, possibly causing a from view. areas of stream impairment and pos- detrimental change in hydrology. An engineering firm was contracted sible solutions, but what about the It became apparent that obtaining to draft a set of plans using A-Jacks to short-term? approvals from the Corps and the Re- protect the population of monardella In 2001, the City of San Diego re- gional Water Quality Control Board without significantly altering the hy- FIGURE 1A. Lopez Canyon, San Diego ca. 1969. Aerial photograph FIGURE 1B. Lopez Canyon, San Diego ca. 2002. Aerial photo- of the canyon prior to the development of the suburban graph of the canyon after the development of the suburban community of Mira Mesa. Note the stream bed of Lopez Creek community of Mira Mesa. Note the enlargement of the stream shown as a meandering white line crossing horizontally in the bed throughout the canyon. 2003 locations of willowy monardella center of the photograph. are shown as white triangles. VOLUME 33:1, JANUARY 2005 FREMONTIA 19 drology of the adjacent channels. Af- ter consultations and site visits with WILLOWY MONARDELLA IN SOUTHERN involved agencies, this third alterna- CALIFORNIA tive was deemed the most feasible. Project construction began on August 11, 2003. Urban Corps of San Willowy monardella (Mon- Diego was hired to conduct the instal- ardella linoides Gary ssp. lation. This non-profit organization, viminea (E. Greene) Abrams) is a which focuses on opportunities to con- state and federally endangered serve our natural resources, provides plant species that is found along job training and educational opportu- drainages within central and nities for young inner-city men and south San Diego County. It is a women ages 18 to 25. Representatives perennial from the Friends of Los Peñasquitos herb that blooms between June and August. Canyon Preserve, Erosion Control This plant species is in the mint family Technologies, and a senior ranger for Los Peñasquitos Canyon Preserve, su- (Lamiaceae) and has a pleasant spearmint aroma. pervised and assisted with the A-Jacks Habitat for willowy monardella is extremely installation. limited. This rare plant species is only found on A small Bobcat or hand tools were terraces along natural drainage courses. As de- used to create the trench for the foot- velopment has increased in San Diego County, ing of the A-Jacks. Once the trench was willowy monardella has been threatened by completed, A-Jacks were installed on floodplain development, increased urban runoff, and invasion by the site in a long, linked chain. A-Jacks weeds. Willowy monardella does not compete well with other plants weigh about 80 pounds each and had and can be choked out by weeds which invade the streamside terraces. to be fitted together exactly to ensure In addition, sparse riparian habitat can turn into thick riparian wood- proper functioning. The installation, land with increased urban runoff, further decreasing habitat areas for which took about one week, was sched- uled to take advantage of the dry sum- willowy monardella. Urban runoff can also erode the streamside mer season when Lopez Creek does terraces where willowy monardella resides, washing the plant and its not flow. Needless to say, it was a la- habitat downstream. The latter example is what has occurred within borious process and the project team, Lopez Canyon. including Urban Corps, maintained a Due to habitat degradation, this plant species is becoming in- great attitude during the hot summer. creasingly rare. Only six known locations continue to persist, with Now that the project has been com- the largest population occurring on military land. Many popula- pleted, City of San Diego staff and the tions in upper Lopez Canyon, Soledad Canyon, and other canyons Friends of Los Peñasquitos Canyon throughout San Diego have been extirpated. It is extremely impor- Preserve hope to preserve and enhance tant that all remaining popu- the natural populations of willowy lations of willowy monar- monardella in Lopez Canyon.