HR: 0800h
AN: H11F-0367    [Abstracts]
TI: Reduced Complexity Modelling of Urban Floodplain Inundation
AU: * McMillan, H K
EM: hkm21@cam.ac.uk
AF: Department of Geography University of Cambridge, Downing Place, Cambridge, CB2 3EN United Kingdom
AU: Brasington, J
EM: james.brasington@geog.cam.ac.uk
AF: Department of Geography University of Cambridge, Downing Place, Cambridge, CB2 3EN United Kingdom
AU: Mihir, M
EM: mm505@cam.ac.uk
AF: Department of Geography University of Cambridge, Downing Place, Cambridge, CB2 3EN United Kingdom
AB: Significant recent advances in floodplain inundation modelling have been achieved by directly coupling 1d channel hydraulic models with a raster storage cell approximation for floodplain flows. The strengths of this reduced-complexity model structure derive from its explicit dependence on a digital elevation model (DEM) to parameterize flows through riparian areas, providing a computationally efficient algorithm to model heterogeneous floodplains. Previous applications of this framework have generally used mid-range grid scales (10$^{1}$-10$^{2}$ m), showing the capacity of the models to simulate long reaches (10$^{3}$-10$^{4}$ m). However, the increasing availability of precision DEMs derived from airborne laser altimetry (LIDAR) enables their use at very high spatial resolutions (10$^{0}$-10$^{1}$ m). This spatial scale offers the opportunity to incorporate the complexity of the built environment directly within the floodplain DEM and simulate urban flooding. This poster describes a series of experiments designed to explore model functionality at these reduced scales. Important questions are considered, raised by this new approach, about the reliability and representation of the floodplain topography and built environment, and the resultant sensitivity of inundation forecasts. The experiments apply a raster floodplain model to reconstruct a 1:100 year flood event on the River Granta in eastern England, which flooded 72 properties in the town of Linton in October 2001. The simulations use a nested-scale model to maintain efficiency. A 2km by 4km urban zone is represented by a high-resolution DEM derived from single-pulse LIDAR data supplied by the UK Environment Agency, together with surveyed data and aerial photography. Novel methods of processing the raw data to provide the individual structure detail required are investigated and compared. This is then embedded within a lower-resolution model application at the reach scale which provides boundary conditions based on recorded flood stage. The high resolution predictions on a scale commensurate with urban structures make possible a multi-criteria validation which combines verification of reach-scale characteristics such as downstream flow and inundation extent with internal validation of flood depth at individual sites.
DE: 1800 HYDROLOGY
DE: 1803 Anthropogenic effects
DE: 1821 Floods
DE: 1860 Runoff and streamflow
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting