Incorporating scientific evidence to change the “levee paradigm” against flooding in the delta of the Ranchería River (Colombia)

Climate change is intensifying flood hazards in coastal areas. In the Ranchería River Delta (Colombian Caribbean), this trend, combined with demographic expansion and the occupation of flood-prone areas, has significantly increased flood risk. Despite its ecological importance, prevailing practices such as land filling and levee construction continue to increase exposure, alter hydrodynamics, and generate long-term residual risk. In addition, the region’s ethnic and cultural diversity, with a strong presence of the Wayuu indigenous people, hinders interaction and dialogue among communities. In this study, different solution alternatives with contrasting approaches were considered, which ranged from conventional engineering to more radical nature-based strategies. Their conception, and preliminary considerations on their expected performance, were co-developed with affected communities and representatives of relevant institutions. After refinement, their performance was explored by systematically assessing a set of technical, economic, environmental, legal, and equity-related criteria by relying on remote sensing, topographic mapping and 2D hydrodynamic modeling. Eventually, the candidate alternatives have been evaluated in a comparative manner within a multicriteria framework. The solution alternative (ADAPT_2) offering the most favorable balance among technical effectiveness, environmental compatibility, and cost, although quite daring, achieved near-unanimous sociocultural acceptance; only one of the 25 participants, representative of the communities involved in the delta region, selected a different alternative (ADAPT_1). This outcome, initially considered utopic, was made possible through a sustained process of community empowerment and mutual trust building. The results demonstrate that participatory approaches can enhance the understanding of the system, foster dialogue and mutual learning, transform risk perception, and support sustainable, adaptive strategies in complex deltaic environments, offering a pragmatic, transferable framework for similar contexts.