NERR RESTORATION SERIES TIJUANA RIVER NATIONAL ESTUARINE RESEARCH Project Location RESERVE (TRNERR) DUNE RESTORATION Tijuana River National Estuarine Research Reserve

Project Duration

1985 - 1986

Project Lead

Paul Jorgensen California State Parks

Current contact: Jeff Crooks – TRNERR Research Coordinator [email protected] Overview 619.575.3613 x.333

Project Size The goal of this project was to restore the barrier dune system at the Tijuana Estuary following dune overwash and inlet closure in 1984. In January 1983, high tide and a 33.5 acres coincidental El Niño storm event washed dune sand into the channels of the estuary resulting in closure of the inlet. As a result of the overwash, an extensive dune Primary Cause of restoration project was initiated to rebuild dunes along the barrier beach in both the Degradation northern and southern arms of the estuary. Dune overwash related to El Niño event

. Project

Partners/Funders

California State Parks

U.S. Fish and Wildlife Service

Pacific Estuarine Research Laboratory, San Diego State University

Tijuana River National

PROJECT GOAL: TO REBUILT AND STABILIZE THE DUNES SYSTEM. Estuarine Research Reserve

Description of Project Activities

Channels in both north and south arm were dredged. In the north arm, approximately 60,000 cubic yards of sand was moved to recreate a dune system approximately 10 feet above mean sea level (MSL). The dune system was artificially shaped to form a continuous berm approximately 200 feet wide at the base and 10 feet high to provide protection from future overwash. In the south arm of the estuary, approximately one mile of dunes was created, totaling about 60,000 yd3 of sand covering approximately 25 acres. Sand deposited in the southern arm was pushed towards the beach to form staggered rows of mounds, which varied from nine–13 feet above MSL. The mounded design was based on natural dunes at San Quintín, Laguna Figueroa and Estero Punta Banda in Baja, California.

In the north arm, four native species were planted from nursery-grown stock. An irrigation system consisting of two parallel lines with drip emitters every 10 feet was installed prior to planting. In all, about 1,400 potted plants and seed were installed. Approximately 50% of the project was set up as an experiment to test five sets of variables. These included: 1) vegetated, rebuilt dunes with fabric fencing; 2) vegetated, rebuilt dunes without fabric fencing; 3) rebuilt dunes without fabric fencing and without revegetation; 4) revegetation with fabric fencing and no rebuilt dunes; and 5) no treatment (control). Plants installed in the south arm were similar to those in the north with the exception that coastal goldenbush was omitted and beach sand verbena (Abronia umbellata) was added. Ecological Outcomes Achieved

The planting was done mid-winter and continuous ocean overwash and heavy winds resulted in a particularly high mortality of plants. Qualitative observations showed that only two species, the red sand verbena and the beach-bur, had a survival rate of 50% or greater.

Monitoring

The shifting sands and overwash made it impossible to mark and quantify individual plants. Qualitative observations were done to assess outcomes.

Lessons Learned

Many lessons were learned from the dune restoration project. It was determined that the northern berm–dune was constructed too far west into the surf zone. Waves destroyed the irrigation lines and precluded fencing the west side of the dunes. In other areas, the irrigation was vandalized and needed constant repair. It was determined that seed application was the best method of establishing plants. Irrigation is advisable but budgets should account for the manpower needed to maintain the lines and emitters. The non-native European sea rocket will invade aggressively in any dune restoration project. Fencing is required to prevent trampling. Again, project budgets should account for maintenance from potential vandalism.

About the National Estuarine Research Reserve System The National Estuarine Research Reserve System is a network of 29 protected areas established by partnerships between the National Oceanic and Atmospheric Administration and coastal states. The reserves protect and conserve 1.3 million acres of coastal and estuarine habitat, while also facilitating improved stewardship of coastal habitats outside of Reserve boundaries. Learn more at coast.noaa.gov/nerrs/