2024 CSDMS meeting-054


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On the impact of coastline anthropogenic geomorphological alterations on flood hazards and upscaling potential for coupled systems.

Sebastian Nash, Pontificia Universidad Catolica de Chile Santiago , Chile. sanash@uc.cl
Cristian Escauriaza, Pontificia Universidad Catolica de Chile Santiago , Chile.
Maria Teresa Contreras, Los Alamos National Laboratory Los Alamos New Mexico, United States.
Antoine Rousseau, INRIA Montpellier , France.

Climate change has led to unprecedented precipitation events in the hyper-arid Atacama Desert of Northern Chile. On the coast of the El Salado watershed, legacy mine tailings infilled the watershed-ocean connection, while the river channel has been altered both by tailings and urbanization. Loss of life and destruction of infrastructure in a large flood event in 2015 resulted from the coupling of anthropogenic geomorphic changes with unusual climate events. We carry out unsteady two-dimensional simulations fully coupled with the sediment concentration to identify the influence of tailing deposits. The analysis incorporates high-resolution topography data from both pre- and post-flood, where the pre-flood scenario represents the presence of tailings, and the post-flood scenario reflects partial erosion of these deposits. Results highlight the important role of topographic alterations in enhancing the hazard to people and critical infrastructure.

Additionally, an upscaling methodology based on porosity is presented for an urban flood simulation in Santiago de Chile, adjacent to the Andean foothills. In this model, topographic information is included at the subgrid-level to optimize CPU time at the cost of some loss in the accuracy of the results. We analyze how accuracy is affected by gradually increasing grid resolution, specifically when estimating flood extent and associated hazards. Results suggest that the cell size can be increased up to the street width, capturing the main flow paths and hazards while significantly reducing the CPU time employed by classical models.

The integration of an upscaling scheme to model concentrated flows coupled with surface dynamics is particularly valuable for comprehensively assessing flood hazards, meeting real-time decision-making needs.