This paper presents a new sub-grid flood inundation model aimed at high computational performance. The model solves the two-dimensional shallow water equations (SWE) by a Godunov-type finite volume (FV) method that uses two nested meshes. Runtime computations are performed at a coarse computational mesh, while a fine mesh is used to incorporate fine resolution information into the solution at pre-processing level. New upscaling methods are separately derived for each of the terms in the SWE based on the integration of the governing equations over subdomains defined by the coarse resolution grid cells. The accuracy and performance of the model are tested through artificial and real-world test problems. Results showed that (i) for the same computational (coarse mesh) resolution, the inclusion of sub-grid information delivers more accurate results than a single-mesh FV model and (ii) for the same accuracy and at low resolution, the proposed methods improve computational performance.

本文提出了一种新的子网格洪水淹没模型，旨在提高计算性能。该模型通过使用两个嵌套网格的 Godunov 型有限体积 (FV) 方法求解二维浅水方程 (SWE)。运行时计算在粗计算网格上执行，而细网格用于在预处理级别将精细分辨率信息合并到解决方案中。基于粗分辨率网格单元定义的子域上的控制方程的积分，为 SWE 中的每个项分别推导出新的升级方法。通过人工和现实世界的测试问题来测试模型的准确性和性能。结果表明 (i) 对于相同的计算（粗网格）分辨率，