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Flood Modelling and Hazard Assessment for Extreme Events in Riverine Basins

Author(s): Roger A. Falconer, Junqiang Xia, Dongfang Liang, Davor Kvooca

Linked Author(s): Roger Falconer

Keywords: Flood modeling, flood hazard, shock capturing, flash floods, river hydraulics

Abstract: Extreme flood events, particularly in short steep river basins, are complex to model computationally and can cause: large loss of property, severe risk to people and debris (such as vehicles) to move and float, which in turn can significantly exacerbate the damage and extent of flooding. It is therefore desirable to be able to model as accurately as possible to predict peak elevations, inundation extent and velocities, and assess the degree of safety of people and vehicles during flash floods. In the paper, details are given to show the need for shock capturing algorithms for accurate modelling of flash floods, followed by new mechanics based formulae and experimental data to assess the flood hazard risk to people and vehicles during extreme flood events. For the mechanics based formulae and experimental data, empirical curves relating water depths and corresponding critical velocities for children and adults, developed supported by previous researchers, are used to assess the degree of people safety, and a new incipient velocity formula is used to evaluate the incipient velocity of vehicles. The developed model is applied to several real case studies of floods, including: Glasgow, Boscastle and Borth in the UK. According to the analysis of model predictions, the following conclusions have been obtained: (i) simulated results for the Glasgow flood show that children would be in danger of standing in the flooded streets in a small urban area; and (ii) simulations for the Boscastle flood indicate that vehicles in the car park would be flushed away by the high velocity flood, which indirectly testified to the predictive accuracy of the incipient formula for vehicles. Therefore, the developed integrated TVD model can be used to assess flood hazard risk to people and vehicles in flash floods, and these predictions can be used in flood risk management, particularly for the short steep river basins prevalent in many countries


Year: 2017

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