Finding an Optimum Grid Size for Numerical Simulations of Dam-break Flow Using Open-Access Digital Elevation Models

Abstract

This work presents numerical simulations for dam-break flow with open-access digital elevation models (DEMs). The objective is to find an optimum grid size for the simulations in terms of accuracy and computational cost. A hypothetical breaching case of Batutegi dam in Indonesia was selected as a case study. Three DEM types with different spatial resolutions, i.e. MERIT-Hydro (∼90 m), ALOS (∼30 m), and DEMNAS (∼8.1 m), were employed. For each DEM, the numerical simulations were performed using four grid sizes, from the lowest to the finest resolution, i.e. 200 m, 90 m, 50 m, and 20 m. All simulations were carried out on a desktop consisting of 10 cores/20 threads with an in-house code NUFSAW2D, enabling parallelization, where double precision arithmetic was used. It was observed that using the computational grid size finer than 50 m produces no longer significant differences of the maximum inundation boundary, maximum depth, maximum velocity, and average depth. This study would be useful for engineers and decision makers, when performing dam-break simulations using DEMs in a framework of an early-warning system.