A Spatial Framework for Blue-Green Infrastructure to Reduce Flood and Landslide Risk in Data-Scarce Tropical Catchments

Abstract

Colombia’s mountainous regions face growing exposure to compound natural hazards (particularly floods and landslides) driven by climate variability, rapid land-use change, and limited institutional capacity. Traditional mitigation strategies remain inadequate, especially in decentralized, data-scarce areas. This study presents an integrated, spatial decision-support framework for multihazard risk reduction using the Blue-Green Infrastructure (BGI) as a nature-based planning solution. Focusing on the Guarapas River catchment in Huila, Colombia, the framework uses the analytic hierarchy process and weighted linear combination to develop spatial risk indices and BGI suitability maps for four intervention types: upland forests, rivers and floodplains, ponds/lakes, and inland wetlands. Validation with historical hazard records confirms the model’s capacity to identify high-risk zones despite data limitations. Results indicate that over 60 percent of the catchment is highly suitable for at least one BGI element, and integrated implementation can reduce modeled risk levels by up to 55 percent. A multiplicative model was applied to simulate cumulative risk reduction, emphasizing the synergistic impact of layered BGI interventions. By intersecting risk and suitability outputs, the study identifies priority zones for investment and offers a scalable, evidence-based tool for climate-resilient spatial planning. The framework advances multihazard assessment and demonstrates the strategic value of BGI in transitioning from reactive to proactive disaster management, especially in low-resource settings.