The LISFLOOD-FP is a raster-based hydrodynamic model originally developed by the University of Bristol. It has undergone extensive development since conception and includes a collection of numerical schemes implemented to solve a variety of mathematical approximations of the 2D shallow water equations of different complexity.
The local inertia solver, known as the ACC solver, is widely used to simulate floods with gradually-varying, subcritical flow over sufficiently rough surfaces with Manning’s coefficient of at least 0.03. It has a version with CPU-specific optimisations and enhanced with a subgrid channel model (Neal et al., 2012, 2018).
LISFLOOD-FP also includes second-order discontinuous Galerkin (DG2) and first-order finite volume (FV1) solvers of the full shallow water equations for modelling a wide range of flows, including rapidly-propagating, supercritical flows, shock waves, or flows over very smooth surfaces. The DG2/FV1 solvers are parallelised for the multi-core CPU architecture, but do not integrate with the subgrid channel model nor with the CPU-specific optimisations.
In an attempt to decrease the computational costs of running flooding simulations, the ACC, FV1 and DG2 solvers have also been accelerated using Graphics Processing Units (GPUs) to exploit their greater degree of parallelisation (Shaw et al., 2021).
The suitable applications for each of the aformentioned solvers of LISFLOOD-FP are summarised in the table below, along with their potential limitations.
|ACC||Fluvial flooding; Pluvial flooding on catchment-scale resolutions||Not recommended for supercritical flows, e.g., thin flows in pluvial flooding simulations at fine resolution|
|FV1||Fluvial and Pluvial flooding; Dam-breaks||Might fail in capturing small-scale transients of flows|
|DG2||Fluvial flooding; Dam-breaks; tsunamis; Flows around hydraulic structures||High computational cost for large-scale applications; Restrictive time-step for applications that involve thin flows|
The latest version of LISFLOOD-FP includes a new solver, known as the non-uniform ACC solver. The non-uniform grid is generated by the application of the multiresolution analyses (MRA) of multiwavelets (MWs) on the Galerkin projecion of the topography data of a digital elevation model (DEM). The ACC solver is adapted on this non-uniform grid without any grading across resolution levels. An overview of the technical background of the non-uniform ACC solver is available in the following online preprint. An overview of the updates to the LISFLOOD-FP workflow, including the new parameters required for the non-uniform ACC solver and video tutorials for reproducing a series of real-world catchment- and urban-scale case studies, are provided in a dedicated section: “Using the non-uniform ACC solver”.
The next version of LISFLOOD-FP will include new GPU-parallelised adaptive FV1/DG2 solvers that run on an adaptive grid generated by the MRA of the HW/MW, respectively, whereby adaptive grid refers to a dynamic-in-time non-uniform grid that is generated every timestep. The new solvers, namely the GPU-parallelised MW adaptive DG2 solver, called GPU-MWDG2, will be overviewed in a technical paper. Guidance for running GPU-MWDG2 from LISFLOOD-FP is available in the following section: Using GPU-MWDG2 in LISFLOOD-FP.
The rest of this page includes instructions on how to download, install and run the code of LISFLOOD-FP 8.2 for using the uniform grid DG2 and FV1 solvers.
Guidance is provided on producing the Galerkin polynomial projection of the DEM and initial condition files (with slope-coefficients), and on post-processing the coarse Galerkin polynomial output files to downscale them into a floodplain map at finer resolutions.
The documented instructions are also covered in video tutorials and through realistic case studies.
LISFLOOD-FP 8.0 is cross-platform and can be compiled on Windows or Linux using CMake version 3.13 or above. University of Sheffield users can also compile and run it on the HPC Computing Facilities. The compilation process on each of the platforms is explained below.
Case studies are presented to instruct users on how to set up and run the DG2/FV1/ACC solvers of LISFLOOD-FP. These studies are also useful to identify the most optimal DG2 configuration for the targeted application.
This case study (Smith et al., 2017) is used to explain how to set up and run LISFLOOD-FP for beginners using any of the DG2, FV1 and ACC two-dimensional hydrodynamic solvers on the CPU or the GPU.
This case study (Soares-Frazao and Zech, 2008) is aimed to demonstrate when local slope limiting with DG2 should be applied.
This case study (Néelz and Pender, 2013) is aimed to demonstrate how to handle an inflow boundary condition located inside the computational area, at source point(s).
This case study (Horritt et al., 2010) is particularly aimed to demonstrate how to handle multiple inflow boundary conditions from different source point(s). It is also used to demonstrate a new postprocessing toolkit for producing metrics to evaluate the floodplain extent predictions when comparing the simulation outcomes of two different hydrodynamic solvers.
This case study (Xia et al., 2019) involves overland flow driven by spatially- and temporally-varying rainfall data over a 2500 kilometre square catchment. It is aimed to demonstrate how to use spatially-varying Manning coefficients provided in an input file, along with the new rain-on-grid option of LISFLOOD-FP 8.0. It is also used to demonstrate a new postprocessing toolkit for downscaling coarse-resolution planar DG2 flood maps.
The source code of LISFLOOD-FP8.1 is available under a GNU General Public License v3.0 for any non-commercial use and can be downloaded at 10.5281/zenodo.4073011.
G. Kesserwani, J.L. Ayog and D. Bau (2018). Discontinuous Galerkin formulation for 2D hydrodynamic modelling: trade-offs between theoretical complexity and practical convenience. Computer Methods in Applied Mechanics and Engineering, 342, 710-741.
J. Ayog, G. Kesserwani, J. Shaw, M.K. Sharifian, and D Bau (2021). Second-order discontinuous Galerkin flood model: comparison with industry-standard finite volume models. Journal of Hydrology, 594: 125924.
J. Shaw, G. Kesserwani, J. Neal, P. Bates, and M. K. Sharifian (2021). LISFLOOD-FP 8.0: the new discontinuous Galerkin shallow water solver for multi-core CPUs and GPUs. Development and technical paper, Geoscientific Model Development, 14, 3577–3602.
M. K. Sharifian, G. Kesserwani, A. Chowdhury, J. Neal, and P. Bates (2023). LISFLOOD-FP 8.1: New GPU accelerated solvers for faster fluvial/pluvial flood simulations, Geosci. Model Dev. Discuss..
While the original version of LISFLOOD-FP were set in motion by University of Bristol, the recent versions 8.0 and 8.1 were mainly developed as part of the SEAMLESS-WAVE project lead by Georges Kesserwani in University of Sheffield, who is main contact about these versions.
The main GPU kernels for the FV1 and DG2 solvers were initiated by James Shaw during his postdoctoral research, before joining The Floow as a senior software engineer. Further developments were mainly carried out by Mohammad Kazem Sharifian, including the GPU kernels of the ACC solver for the uniform and non-uniform grids. Mohammad is now a Flood Modeller at RMS (Moody’s Analytics Company) and is happy to receive enquiries about the software, bug reports, feature requests, or any relevant matter that needs the community’s attention.