Beach Impact Comparison Study
Tijuana River vs. San Antonio de los Buenos (SAB) Creek
Of the pollutants commonly found in transboundary flows, untreated wastewater, which contains harmful pathogens, poses the greatest risk to human health. To minimize human contact with untreated wastewater during transboundary flow events, local governments mandate beach closures, reducing access to fishing, swimming, surfing, other recreational activities, and tourism.
Due to public health and beach water quality concerns, Scripps Institution of Oceanography developed an estuary and ocean model to evaluate the impacts of “infrastructure solutions to improve shoreline water quality and reductions on regional beach closures.” Their work analyzed all Tijuana River and SAB Creek transboundary flows during 2017 and concluded:
- “Eliminating or dramatically reducing [wastewater flows to SAB Creek] has the strongest benefit to the City of Imperial Beach, Silver Strand State Beach, and City of Coronado.”
- In wet season the Tijuana River causes two-thirds of closures and SAB Creek one-third of closures.
- SAB Creek “is the dominant source that leads to regional beach closures” year round, and especially during the dry season (109 days during the year).
- Beach closure estimates are made based on wastewater bacteria concentrations and may not correlate with actual beach closures due to additional factors.
Graph is generated using Scripps Institution of Oceanography findings. Graph shows annual impacts to Imperial Beach. Similar conclusions are drawn at Playas Tijuana, Silver Strand State Beach, and Hotel del Coronado.
Source: Feddersen, F., X. Wu, and S. N. Giddings, Modeling impacts of various wastewater and stormwater flow scenarios on San Diego South Bay and Tijuana beaches, Tech. Report for the North American Development Bank, November 2020.