Modelling floods in urban areas and representation of buildings with a method based on adjusted conveyance and storage characteristics Zoran Vojinovic, Solomon Seyoum, Mwanaisha H. Salum, Roland K. Price, Ahmad K. Fikri and Yared Abebe ABSTRACT The present paper reviews several approaches that can be used in capturing urban features in coarse resolution two-dimensional (2D) models and it demonstrates the effectiveness of a new approach against the straightforward 2D modelling approach on a hypothetical and a real-life case study work. The case study work addresses the use of coarse grid resolutions in 2D non-inertia models. The 2D non- inertia model used solves continuity and momentum equations over the cells of the coarse model while taking the minimum elevation as a surface level. The volume stored in every cell is calculated as a volume-depth relationship. In order to replicate restriction in conveyances in x–y directions of fine resolution models due to building blocks, the friction values of the coarse-resolution model are adjusted to match the results of the high-resolution model. The work presented in this paper shows the possibility of applying a 2D non-inertia model more effectively in urban flood modelling applications whilst still making use of the high resolution of topographic data that can nowadays be easily acquired. Zoran Vojinovic (corresponding author) Solomon Seyoum Mwanaisha H. Salum Roland K. Price Ahmad K. Fikri Yared Abebe Department for Hydroinformatics and Knowledge Management, UNESCO-IHE, Westvest 7, 2601 DA Delft, The Netherlands E-mail: Z.Vojinovic@unesco-ihe.org Key words | 2D models, flood modelling, spatial resolution, topography, urban areas ABBREVIATIONS 1D One dimensional 2D Two dimensional ADI Alternating direction BCR Building coverage ratio CRF Conveyance reduction factor DTM Digital terrain model DSM Digital surface model GIS Geographic information system LiDAR Light detection and ranging TIN Triangulated irregular network INTRODUCTION Urban flooding has become an increasingly important problem and growing issue around the world. Since it continues to be regarded as an almost inevitable danger, the development of cost-effective flood mitigation strategies has become of the utmost importance for many cities, and particularly for those cities in developing countries where the financial resources for recovery from flood-related disasters are almost nonexistent. Certainly, the use of physically-based computational modelling coupled with geographic information system (GIS) mapping is invaluable for this purpose. With instantiated models and specialist GIS flood mapping techniques it is possible to explore generation of floods and evaluate effects of different measures in response to any extreme event. Geo-referenced results from one-dimensional (1D) or 1D/two-dimensional (1D/2D) coupled models can readily be used to evaluate the potential scenario, communicate the risk of flooding and to gain insights into the nature of floods and their impacts on communities. The knowledge gained can then be transformed into a set of effective and acceptable actions to be taken by all who are affected (see, for example, Mynett & Vojinovic ). 1150 © IWA Publishing 2013 Journal of Hydroinformatics | 15.4 | 2013 doi: 10.2166/hydro.2012.181 Downloaded from http://iwaponline.com/jh/article-pdf/15/4/1150/387149/1150.pdf by guest on 06 July 2023