Natural Flood Risk Management in Tropical Southeast Asia: Prospects in the Biodiverse Archipelagic Nation of the Philippines

ABSTRACT

Natural flood management (NFM) has gained prominence as a flood risk management approach in temperate settings but lacks extensive applied examples and evidence in tropical settings, despite significant ecosystem degradation and high flood risk exposure. Tropical river catchments often experience highly variable hydrographs (i.e., prone to flash floods) and intense rainfall from monsoon and typhoon‐dominated weather systems that can cause landslides and sediment‐transporting river flows. These conditions provide a backdrop to the prospects for NFM in tropical Southeast Asia, of which the Philippines is representative. Catchments in the country are typically small and thus associated with short hydrological response times. They are also characterized by diversity of river types, high rates of lateral mobility, extensive downstream urbanization, and complex land use mosaics at the coast. Consideration of NFM as a conceptual framework in the Philippines may enable conversations about adapting existing flood risk management approaches. To explore these NFM alternatives, we conceptualize opportunities in a typical catchment that we divide into four nested, connected parts: managing headwaters as sponges; conserving and restoring river and floodplain width; blue‐green infrastructure in urban areas; and maintaining and creating space for water in fluvial‐coastal settings. There is potential in countries such as the Philippines to adopt NFM strategies that have shown promise in temperate regions and select Southeast Asian countries, where emerging evidence supports their effectiveness. Monitoring tropical NFM interventions remains crucial to gather evidence supporting broader application of nature‐based solutions for flood risk mitigation and biodiversity loss in tropical Southeast Asia.