Flooding can cause major disruptions in cities, and lead to significant impacts on people, the economy and on the environment. These impacts may be exacerbated by climate and socio-economic changes. Resilience thinking has become an important way for city planners and decision makers to manage flood risks. Despite different definitions of resilience, a consistent theme is that flood resilient cities are impacted less by extreme flood events. Therefore, flood risk professionals and planners need to understand flood impacts to build flood resilient cities. This paper presents a state-of-the-art literature review on flood impact assessment in urban areas, detailing their application, and their limitations. It describes both techniques for dealing with individual categories of impacts, as well as methodologies for integrating them. The paper will also identify future avenues for progress in improving the techniques.

Recent developments in flood modeling have led to the concept of coupled (sewer/surface) hydraulic models. In this paper two coupled models are examined; a one-dimensional (1D) sewer model coupled with a 1D surface network model (1D/1D) and a 1D sewer model coupled with a two-dimensional (2D) surface flow model (1D/2D). Flow over the terrain is better modeled by 2D models, whereas in confined channels 1D models provide a good approximation with less computational effort. This paper presents a comparison of the simulation results of 1D/1D model and a 1D/2D model. The methodology adopted for setting up the models is outlined and explained in detail as well as the 1D/1D modeling techniques used for reproducing the 1D/2D model results. The surface flow comparison clarifies the limitations of the 1D/1D model and indicates that the definition of the surface pathways, the linking elements sewer/surface, and inclusion of virtual manholes are key factors for setting up a more accurate 1D/1D model.

To achieve fast flood modelling for large-scale problems, a two-dimensional cellular automata based model was developed. This model employs simple transition rules and a weight-based system rather than complex Shallow Water Equations. The simplified feature of cellular automata allows the model to be implemented in parallel environments, resulting in significantly improved modelling efficiency. The model has been tested using an analytical solution and four case studies and the outputs were compared to those from a widely-used commercial physically-based hydraulic model. Results show that the model is capable of simulating water-depth and velocity variables with reasonably good agreement with the benchmark model, using only a fraction of the computational time and memory. In the case of the real world example, the proposed model run times are up to 8 times faster. The rapid and accurate attributes of the model have demonstrated its applicability for quick flood analysis in large modelling systems