A 30 m resolution global fluvial–pluvial–coastal flood inundation model for any climate scenario
Authors: Wing Oliver , Quinn Niall , Uhe Pete , Savage James , Sampson Chris , Addor Nans , Lord Natalie , Collings Tom , Hatchard Simbi , Hoch Jannis , Smith Andy , Cooper Anthony , Bates Joe , Wilkinson Hamish , Himsworth Sam , Probyn Izzy , Haigh Ivan , Neal Jeff , Bates Paul 
Published: February 2023

The past decade has seen considerable advances in the field of global flood modelling. In the 2010s, it began as a niche academic endeavour building models of the order 103 m horizontal resolution. In the 2020s, it is maturing into an established scientific discipline and yields profitable commercial ventures, with global models emerging of the order 101 m resolution.Building on the original 102 resolution global inland flood model of Sampson et al. (2015) &#8211; with a hydraulic engine based on the sub-grid version of the LISFLOOD-FP local inertial formulation of the shallow water equations (Bates et al., 2010; Neal et al., 2012) &#8211; we present the critical advances required to create a ~30 m resolution model of considerably greater fidelity and functionality:Using FABDEM as the underlying elevation grid, a machine-learning correction of the Copernicus global digital surface model to a digital terrain model (Hawker et al., 2022).
Representing river hydrography with MERIT-Hydro (Yamazaki et al., 2019), ensuring the correct alignment of river channels with valley bottoms.
Estimating river bathymetry prior to inundation modelling with a gradually varied flow solver (Neal et al., 2021).
Updating boundary condition generation models with new hydrometric datasets and machine-learning hydrologic regionalization techniques (e.g. Zhao et al., 2021).
Driving a global coastal flood model with a tide&#8211;surge&#8211;wave regional frequency analysis using tide gauges and reanalyses (Sweet et al., 2020).
Implementing known and estimated flood protection measures as a rapid and adaptable post-process.
Generating global climate change factors for fluvial, pluvial, and coastal floods for any plausible 21st century climate state.
Applying climate change factors as a tractable post-process to a set of multi-frequency flood maps.
These updates form the third version of Fathom's global flood maps. We show that these herald a new era of global flood modelling precision and accuracy, with additional utility wrought from linking climate projections to high-resolution true hydrodynamic models at the global scale for the first time. We also chart the road ahead for global flood modelling: outlining the significant data and modelling challenges our community must address to continue on this unprecedented development trajectory.&#160;References:Bates, P., et al. (2010) https://doi.org/10.1016/j.jhydrol.2010.03.027Hawker, L. & Uhe, P., et al. (2022) https://doi.org/10.1088/1748-9326/ac4d4fNeal, J., et al. (2012) https://doi.org/10.1029/2012WR012514Neal, J., et al. (2021) https://doi.org/10.1029/2020WR028301Sampson, C., et al. (2015) https://doi.org/10.1002/2015WR016954Sweet, W., et al. (2020) https://doi.org/10.3389/fmars.2020.581769Yamazaki, D., et al. (2019) https://doi.org/10.1029/2019WR024873Zhao, G., et al. (2021) https://doi.org/10.5194/hess-25-5981-202