GeoFlood (v1.0.0): Computational model for overland flooding

TL;DR

Comparisons validate GeoFlood's capabilities for idealized benchmarks compared to other commonly used models as well as its ability to efficiently simulate highly dynamic floods in complex terrain, consistent with historical field data.

Abstract

This paper presents GeoFlood, a new open-source software package for solving the shallow-water equations (SWE) on a quadtree hierarchy of mapped, logically Cartesian grids managed by the parallel, adaptive library ForestClaw (Calhoun and Burstedde, 2017). The GeoFlood model is validated using standard benchmark tests from Neelz and Pender (2013) as well as the historical Malpasset dam failure. The benchmark test results are compared against those obtained from GeoClaw (Clawpack Development Team, 2020) and the software package HEC-RAS (Hydraulic Engineering Center River Analysis System, Army Corps of Engineers) (Brunner, 2018). The Malpasset outburst flood results are compared with those presented in George (2011) (obtained from the GeoClaw software), model results from Hervouet and Petitjean (1999), and empirical data. The comparisons validate GeoFlood's capabilities for idealized benchmarks compared to other commonly used models as well as its ability to efficiently simulate highly dynamic floods in complex terrain, consistent with historical field data. Because it is massively parallel and scalable, GeoFlood may be a valuable tool for efficiently computing large-scale flooding problems at very high resolutions.

Figures (19)

• Figure 1: The left figure depicts an adaptively refined ForestClaw solution to the shallow-water equations on a Cartesian grid in the quadtree layout on a single block. The right figure depicts three adjacent adaptive levels, each with an $8~\times~8$ simulation grid (with thick borders) and a layer of ghost cells (shaded gray). Quadrant boundaries are indicated by thick lines.
• Figure 2: Spatial domain displaying the inflow location (boundary condition) along $20$ m of the left boundary ($x=0$ and $990\le y \le 1010$ m). Level-set contours are shown for the depths $h=10$ and $h=20$ cm at $t=1$hour (black dashed curves) and $t=3$hours (black solid curves), indicating the nearly radially symmetric solution. The diagonal (green dashed) and horizontal (orange dashed) lines depict the two transects considered in Figure \ref{['fig:transect']}. The six control points ($+$ symbols) indicate the location for time series depicted in Figure \ref{['fig:depth_']} and Figure \ref{['fig:depth_45']}.
• Figure 3: Inflow hydrograph imposed at the inlet boundary
• Figure 4: Cross-section of depths along (a) a horizontal line $7$m above the horizontal central line through the domain and (b) tilted at $45^{\circ}$ to the horizontal at time $t = 1$hour for both HEC-RAS, GeoFlood, and GeoClaw. Refer to Figure \ref{['fig:test4bed']} for a depiction of the horizontal and tilted lines.
• Figure 5: Overhead map perspectives of the water surface elevation at various times for both the HEC-RAS (a-c) and GeoFlood (d-f) simulations. The HEC-RAS simulation was performed on a $5$m uniformly structured grid with $200 \times 400$ grid cells while GeoFlood was simulated on an adaptively refined grid with max-level = $4$, min-level = $1$, starting on the coarsest mesh of $50 \times 50$ level 0 grid blocks in a $2 \times 4$ block arrangement to finest mesh of $1600 \times 3200$ grid cells at $0.6$m grid cell resolution. At $t = 1$ and $t = 2.5~\unit{hours}$, grid lines for HEC-RAS and the maximum refinement level in GeoFlood are omitted from the plots.