Over 20% of La Union, Ilocos Sur coasts show erosion – UP study

SAN FERNANDO CITY, La Union — More than one-fifth of assessed shoreline areas in La Union and Ilocos Sur showed erosion from 1977 to 2022, a University of the Philippines study found, warning against further coastline development.

Research led by the state university's Marine Science Institute (UP-MSI) found that 22.4% of assessed shoreline areas in La Union and 22.2% in Ilocos Sur have eroded.

The rates were lower in Ilocos Norte at 17.7% and Pangasinan at 11.1%.

Fernando Siringan of UP-MSI presented the findings at the Region 1 Coastal Resilience and Biodiversity Protection Forum on September 22. He identified the coastal stretch from Bauang to Santo Tomas and Agoo in La Union as particularly prone to erosion.

"You should not put development there, as much as possible, and leave it alone," Siringan said of areas with rapidly changing shorelines.

Researchers used historical maps and Landsat satellite images to track shoreline changes. The study notes erosion trends, possible causes and sediment movement along selected coastlines in the four Ilocos Region provinces to help guide local government planning.

The study identified shifting river channels, quarrying along beaches and rivers, engineering works that restrict sediment flow, sea-level rise, land subsidence and typhoons as factors contributing to erosion. Siringan stressed that the causes and severity vary by location.

Residents and environmental groups have raised concerns over dredging and magnetite extraction in parts of La Union and Ilocos Sur, warning these could worsen shoreline loss and affect fisheries.

Siringan said coastal development decisions should combine scientific data and satellite observations with the experiences of communities that have witnessed long-term changes in beaches, rivers and flooding.

His team's coastal erosion research began in La Union nearly three decades ago and later expanded across the Ilocos Region with support from the Department of Science and Technology and partnerships with Mariano Marcos State University and Don Mariano Marcos Memorial State University.

A 2015 study led by Siringan for the Ilocos Sur provincial government similarly warned that such activities in vulnerable areas could further destabilize already eroding shorelines.