Abstract
Rapid floods induced by extreme precipitation are common events in regions near the Andes mountain range. Growing urban development, combined with the changing climate and the influence of El Niño, have increased the exposure of the population in many regions of South America. Simulations of flash floods in these watersheds are very challenging, due to the complex morphology, the insufficient hydrometeorological data, and the uncertainty posed by the variability of sediment concentration. To address these issues, we develop a high-resolution numerical model of the non-linear shallow water equations, coupled with the mass conservation of sediment, and considering the density effects and changes of rheology in the momentum equation. Based on these simulations we develop a real-time early-warning system, by creating a surrogate model or meta-model from the simulations. Using a small set of parameters, we define storms for a wide range of meteorological conditions, and utilize the high-fidelity model results to create a database of flood propagation under different conditions. Through this second model we perform a sophisticated interpolation/regression, and approximate efficiently the flow depths and velocities. This is the first application of its kind in the Andes region, which can be used to improve the prediction of flood hazard in real conditions, employing low computational resources. We also create a framework to develop early warning systems, and to help decision makers and city planners in these mountain regions.
Highlights
Flash floods produced by extreme precipitation events have shown to frequently affect cities and infrastructure in mountain regions
In this investigation we develop two models for studying the propagation of rapid floods in an Andean watershed: (1) We implement a two-dimensional high-resolution numerical model of the shallow-water equations coupled to a hydrological model, to simulate the flood dynamics in complex arbitrary geometries, considering the effects of large sediment concentrations; and (2) We develop a surrogate model based on the results of the high-fidelity approach, which can rapidly calculate new scenarios characterized by a set of parameters that define the hydrometeorological events, using a statistical interpolation in the parameter space
The simulation of flood hazards by extreme precipitation in mountain streams requires numerical models capable of capturing complex flows that are influenced by the geomorphic features of the channel, and by high sediment concentrations that are common in these regions
Summary
Flash floods produced by extreme precipitation events have shown to frequently affect cities and infrastructure in mountain regions. High-resolution models might have significant computational costs, which can prevent the timely prediction of the flood propagation necessary for early warning systems, especially when the uncertainty of the flood conditions requires the evaluation of multiple possible scenarios of the event In this investigation we develop two models for studying the propagation of rapid floods in an Andean watershed: (1) We implement a two-dimensional high-resolution numerical model of the shallow-water equations coupled to a hydrological model, to simulate the flood dynamics in complex arbitrary geometries, considering the effects of large sediment concentrations; and (2) We develop a surrogate model based on the results of the high-fidelity approach, which can rapidly calculate new scenarios characterized by a set of parameters that define the hydrometeorological events, using a statistical interpolation in the parameter space.
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