Flood risk-benefit assessment to support management of flood-prone lands

Abstract

Flood risk assessments often overlook benefits of floodplain use and the influence of coping capacity. Herein we present a classic flood risk analysis, but simultaneously evaluate benefits of flood-prone land use in Candaba, Philippines. By combining simulated flood probabilities with both damage and benefit functions, we estimate agricultural damages and livelihood benefits over flood hazards of varying frequency. We find that concurrent evaluation of both damages and benefits provides more complete information on which flood risk reduction decisions may be based. In Candaba, although “risky” uses of flood-prone land are associated with rice-crop damages, livelihood benefits exceed risks by a large margin (US $58 million) across the range of investigated flood hazards. Even considering risk, net benefits of direct human floodplain use far exceed benefits provided when direct “risky” human uses are excluded (difference of $85–87 million). We also find that individual coping strategies (adapting crop cycles to the flood pulse or shifting from farming to seasonal fishing) may minimise flood losses while supporting livelihood benefits (net benefit of $125 million). Risk-benefit analysis can support floodplain management by elucidating practices that yield maximum socio-ecological benefits for the minimum flood risk.