HEC-RAS hydraulic model as a tool for flood risk evaluation at local scale: Case study of two urban sites in Quinsaloma, Ecuador

In Quinsaloma, Los Ríos province, Ecuador, river floods are a recurring hazard exacerbated by deforestation and uncontrolled urban spread. They cause significant material losses. To reduce the risk and ensure efficient use of limited financial resources, local governments need to apply technological tools. Thus, this study applied the HEC-RAS hydraulic model (US Army Corps of Engineers, Hydrologic Engineering Center, Davis, USA) flood simulation tool to evaluate flood risk in the Las Palmitas and 12 de Octubre residential areas, located close to the Umbe River.

The required spatial layers were derived from a 12.5 m DEM obtained from the Alaska Satellite Facility online archive. Model validation was carried out at 20 random points using the Kappa coefficient, compared against historical flood data. Vulnerability assessment was conducted using the SNGR (National Risk Management Secretariat) methodology.

Modelled flood depth varied between 0.0001 m and 2.45 m. Modelling identified 36 ha of floodable area: Las Palmitas (9 ha) and 12 de Octubre (27 ha). Validation resulted in Kappa coefficients of 0.612 and 0.538 for 12 de Octubre and Las Palmitas, respectively, showing good agreement with historical data. The vulnerability assessment demonstrated high flood risk (high threat–high vulnerability) in Las Palmitas, whereas the 12 de Octubre site was at moderate flood risk (moderate threat–moderate vulnerability).

The study confirmed that HEC-RAS is an efficient tool for flood risk assessment at local scale, providing reliable data for decision-makers. Low-elevation areas are more flood-prone; their exact delimitation is a major factor for efficient mitigation strategies to reduce flood risk and ensure environmental safety for the population and infrastructure. Further research will extend HEC-RAS application to model sediment transport and rainwater pipe infrastructure planning at the same sites.