San Dieguito Lagoon Surveys

Dredging was required in San Dieguito Lagoon to maintain tidal flow and restore nominal depths as part of lagoon restoration. Prior to dredging, patches of eelgrass (Zostera spp) were observed in the area of potential effect. The loss of eelgrass during dredging was mitigated by transplanting eelgrass in nearby suitable habitat, a basin within the Lagoon. Three mitigation sites within the basin, as well as a nearby reference site, were surveyed by MBC divers at prescribed intervals for five years to document the success of the transplant. By the third year, both eelgrass coverage and turion density exceeded success criteria stipulated in the Southern California eelgrass Mitigation Policy. At the completion of the project, MBC conducted a sidescan sonar survey of the entire mitigation basin to determine approximate coverage of eelgrass. A subcontractor also performed an infrared/near-infrared aerial drone survey, and the results were compared to determine the variability of results among methods.