Philippine island uses oyster shells to fight floods

Residents of Pamarawan Island in the Philippines are using bamboo poles and discarded oyster shells to weaken waves and manage flooding instead of relying only on concrete seawalls.

The island north of Manila has about 3,000 residents and faces storm surges, land subsidence and rising seas linked to climate change. The city government of Malolos began studying the project with a Dutch engineering consultancy, and workers started installing bamboo poles packed with brushwood by May last year.

Workers have also been building an oyster-shell breakwater about 100 metres offshore. Project manager Lyana Galang said the shell barrier is meant to reduce wave impact before water reaches the community and to work with bamboo sediment traps.

Mayor Christian Natividad said the installations cover about 14 hectares along Manila Bay and cost 70 million pesos, or $1.1 million, including maintenance. He said a comparable concrete seawall would cost about 90 million pesos and estimated the bamboo will need replacing every five years.

The first phase was completed in late 2025. Residents said the barriers have softened waves and helped keep floodwaters back during typhoons and monsoon rains this year.

The long-term effectiveness remains uncertain. Natividad said a scientific assessment due next year will determine whether mangrove planting can begin, with success expected to become clearer over the next decade as sediment builds up and stabilises the seabed.