Simple spatially-distributed models for predicting flood inundation: A review Neil M. Hunter a, ⁎ , Paul D. Bates b , Matthew S. Horritt c , Matthew D. Wilson d a JBA Consulting, South Barn, Broughton Hall, Skipton, North Yorkshire, BD23 3AE, UK b School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1SS, UK c Halcrow Group Ltd, Burderop Park, Swindon, Wiltshire, SN4 0QD, UK d Department of Geography, University of Exeter in Cornwall, Tremough Campus, Treliever Road, Penryn, Cornwall, TR10 9EZ, UK Accepted 16 October 2006 Available online 21 April 2007 Abstract In this paper we review recent progress in the use of reduced complexity models for predicting floodplain inundation. We review the theoretical basis for modelling floodplain flow with simplified hydraulic treatments based on a dimensional analysis of the one-dimensional shallow water equations. We then review how such schemes can be applied in practice and consider issues of space discretization, time discretization and model parameterisation, before going on to consider model assessment procedures. We show that a key advantage of reduced complexity codes is that they force modellers to think about the minimum process representation necessary to predict particular quantities and act as a check on any tendency to reductionism. At the same time, however, the use (compared to standard hydraulic codes) of strong simplifying assumptions requires us to also address the question “how simple can a model be and still be physically realistic?” We show that by making explicit this debate about acceptable levels of abstraction, reduced complexity codes allow progress to be made in addressing a number of long-standing debates in hydraulics. © 2007 Elsevier B.V. All rights reserved. Keywords: Floods; Reduced complexity modelling; Hydraulic modelling; Inundation extent; Remote sensing Contents 1. Introduction ..................................................... 209 2. Reduced complexity modelling of flood inundation: theoretical considerations .................... 209 2.1. Validity of simplified approximations to the shallow water equations .................... 210 3. Reduced complexity modelling of flood inundation: practical considerations ...................... 212 3.1. Governing equations and numerical solution schemes .............................. 212 3.1.1. Discretization of time ........................................ 212 3.1.2. Discretization of space ........................................ 213 Geomorphology 90 (2007) 208 – 225 www.elsevier.com/locate/geomorph ⁎ Corresponding author. Tel.: +44 1756 799919; fax: +44 1756 799449. E-mail addresses: neil.hunter@jbaconsulting.co.uk (N.M. Hunter), paul.bates@bristol.ac.uk (P.D. Bates), horrittm@halcrow.com (M.S. Horritt), matthew.d.wilson@exeter.ac.uk (M.D. Wilson). 0169-555X/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.geomorph.2006.10.021