Evaluation of the potential of friction surface analysis in modelling hurricane wind damage in an urban environment

This research considered the use of friction surface analysis as a means of modelling the vulnerability of an urban topography to hurricane wind effects (wind speed force and windborne debris). Isotropic and anisotropic surfaces of Miami, Florida, USA, were derived from tax building age, and LIDAR building height data, to act as a test area for the methodology. The isotropic surface modelled the key vulnerabilities of individual buildings within the study area, whilst the anisotropic surface considered the varying effects due to wind directionality. The results from the model indicate the logical effect of most damage occurring on surfaces that directly face the oncoming wind, and this is only minimised on those surfaces that are sheltered by larger buildings. This directionality effect on results is validated by damage records for actual hurricane events that are recorded in the literature, as well as the patterns observed on Central Miami landmarks after Hurricane Wilma in 2005. These results represent a simplistic GIS approximation of the phenomena in a specific urban environment, which do not take into account more complex factors linked to urban ‘roughness’ and turbulence effects. To model these complexities would require a multidisciplinary approach involving meteorologists and engineers. This research, however, indicates that the vulnerability surface produced by the friction surface analysis has potential as a tool to assess hurricane impact in a selected area which could be of use in implementing mitigation initiatives, disaster recovery planning and assessing financial loss. This represents a deterministic approach, but calibration of the results against building exceedance probability damage curves suggests that this methodology could be correlated with stochastic catastrophe model methodologies. The deterministic nature of the methodology means that it can be used at any location, but the derived friction layers must be carefully considered on a locality-by-locality basis.