Evaluating scale and roughness effects in urban flood modelling using terrestrial LIDAR data

摘要

This paper evaluates the results of benchmark testing a new inertialformulation of the St. Venant equations, implemented within the LISFLOOD-FPhydraulic model, using different high resolution terrestrial LiDAR data(10 cm, 50 cm and 1 m) and roughness conditions (distributed and composite) inan urban area. To examine these effects, the model is applied to ahypothetical flooding scenario in Alcester, UK, which experienced surfacewater flooding during summer 2007. The sensitivities of simulated waterdepth, extent, arrival time and velocity to grid resolutions and differentroughness conditions are analysed. The results indicate that increasing theterrain resolution from 1 m to 10 cm significantly affects modelled waterdepth, extent, arrival time and velocity. This is because hydraulicallyrelevant small scale topography that is accurately captured by theterrestrial LIDAR system, such as road cambers and street kerbs, is betterrepresented on the higher resolution DEM. It is shown that altering surfacefriction values within a wide range has only a limited effect and is notsufficient to recover the results of the 10 cm simulation at 1 m resolution.Alternating between a uniform composite surface friction value (n = 0.013)or a variable distributed value based on land use has a greater effect onflow velocities and arrival times than on water depths and inundationextent. We conclude that the use of extra detail inherent in terrestriallaser scanning data compared to airborne sensors will be advantageous forurban flood modelling related to surface water, risk analysis and planningfor Sustainable Urban Drainage Systems (SUDS) to attenuate flow.