Abstract
A variety of flood models and commercial flood simulation software are provided in the literature, with different accuracies and precisions changing from coarse to fine, depending on model structure and detailed descriptions of basin and hydrologic properties. These models generally focus on river processes, taking overland processes as inputs of 1D or 2D hydrodynamic or hydrologic river flow models. Due to the discrete structure of overland flow and unknown-dynamic boundary conditions, such classical approaches are not cable of fast and reliable spatio–temporal estimations for overland flows, and require detailed and well-organized spatial data that cannot be immediately obtained during an emergency. A spatially-distributed Geographical Information Systems (GIS) based flood model is developed in this study to simulate overland floods, using cellular automata principles. GIS raster cells are considered hydrologic homogeneous areas throughout which hydrologic properties remain constant. Hydrodynamic flow principles, conservations of mass, momentum and energy are applied at pixel level to simulate floodwaters. The proposed GIS model is capable of directly manipulating spatio–temporal pixel level data (e.g., topography, precipitation, infiltration, surface roughness etc.) for modeling of rainfall-induced overland floods; therefore, it can provide fast, temporal and spatial flood depth estimations as well as maximum flood depths and times of concentration for all pixels throughout a study area. The model is quite simple and easy to apply via easily creatable GIS input layers, and is thus very convenient for preliminary engineering applications that need quick and fast response. Its main advantage is that it does not need a predefined flood boundary and boundary conditions. This advantage is especially valuable for coastal plains where delineation of a basin is generally too difficult. Floodwaters of Cyclone Nargis/Myanmar were simulated to test the model. Sensitivity analyses were applied to evaluate the effects of the model parameters (i.e., surface roughness and infiltration rates) on simulation results. The study shows that the proposed GIS model can be readily applied for the fast and inexpensive modeling of rainfall caused floods in areas where flood boundaries and boundary conditions cannot be clearly identified.
Highlights
Experiences have shown that the only reliable way to prevent flood damage and casualties is to keep people away from floodwaters [1,2]
This study proposes an overland flood model that relies on cellular automata, fast aiming and empirical Geographical Information Systems (GIS) modeling
GIS grids depicting flood depths for the 0th, 12th, 24th, 36th, 48th, 60th hours (Figure 7) and GIS grids depicting maximum flood depth and concentration time (Figure 8) were obtained as flood simulation results
Summary
Experiences have shown that the only reliable way to prevent flood damage and casualties is to keep people away from floodwaters [1,2]. Hydrodynamic river-induced flood models account successfully for surface processes [9,16,17,18] provided that there is a continuity in floodplain flows within a well-defined boundary [5,8,13,14]. They have high accuracy and spatial/temporal capabilities in flood modeling but suffer from some difficulties in practice when evaluating rainfall induced overland floods. Most of the population potentially under the threat of threat of flooding live in such areas, where the main economical/agricultural activities take place,
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