A Two-Dimensional hydrodynamic framework for simulating oil spills in rivers and floodwaters

Floods are the most frequent natural disasters, and their frequency and intensity are expected to increase under climate change, leading to heightened vulnerability of critical infrastructure. Such conditions amplify the likelihood of cascading effects, including industrial accidents (e.g., Natech - Natural Hazard Triggering Technological Disasters). Moreover, floods often can transport hazardous contaminants over long distances, generating significant impacts on ecosystems and human health. While numerous models exist for marine oil dispersion, their application to river and floodplain environments remains limited. Available models are often non-open access, computationally intensive, and require extensive input data, restricting their usability for rapid-response scenarios or studies involving multiple simulation runs. To address this gap, the present study develops a simplified crude oil dispersion module for floodwaters, integrated into the CAESAR-LISFLOOD model (a morphodynamic Landscape Evolution Model). This approach provides a balance between physical reliability, computational efficiency, and ease of use, making it suitable for rapid-response applications, scenario analysis, and large-scale studies. The model was tested on two case studies with differing levels of hydraulic and topographic complexity and benchmarked against the oil dispersion module implemented in Telemac 2D. Results indicate that CAESAR-LISFLOOD reproduces dispersion patterns, mean concentrations, and contaminated areas with good consistency. Moreover, depending on the spatial and temporal resolution of the simulations, CAESAR-LISFLOOD reduces computational times by 60–80% compared to Telemac 2D while maintaining a sufficiently robust physical representation for lowland floods with subcritical flows. This significant reduction in computational demand, combined with reliable physical performance, highlights the suitability of the model for rapid-response simulations, repeated scenario analyses, and risk assessment studies in flood-prone areas.