Floodplain friction parameterization in two‐dimensional river flood models using vegetation heights derived from airborne scanning laser altimetry

Two-dimensional (2-D) hydraulic models are currently at the forefront of research into river flood inundation prediction. Airborne scanning laser altimetry is an important new data source that can provide such models with spatially distributed floodplain topography together with vegetation heights for parameterization of model friction. The paper investigates how vegetation height data can be used to realize the currently unexploited potential of 2-D flood models to specify a friction factor at each node of the finite element model mesh. The only vegetation attribute required in the estimation of floodplain node friction factors is vegetation height. Different sets of flow resistance equations are used to model channel sediment, short vegetation, and tall and intermediate vegetation. The scheme was tested in a modelling study of a flood event that occurred on the River Severn, UK, in October 1998. A synthetic aperture radar image acquired during the flood provided an observed flood extent against which to validate the predicted extent. The modelled flood extent using variable friction was found to agree with the observed extent almost everywhere within the model domain. The variable-friction model has the considerable advantage that it makes unnecessary the unphysical fitting of floodplain and channel friction factors required in the traditional approach to model calibration. Copyright  2003 John Wiley & Sons, Ltd.

[1]  Stephen E. Darby,et al.  Predicting Stage-Discharge Curves in Channels with Bank Vegetation , 1996 .

[2]  J. M. Hervouet,et al.  Finite Element Algorithms for Modelling Flood Propagation , 1994 .

[3]  D. Mason,et al.  Image processing of airborne scanning laser altimetry data for improved river flood modelling , 2001 .

[4]  P. Bates,et al.  Predicting floodplain inundation: raster‐based modelling versus the finite‐element approach , 2001 .

[5]  D. Mason,et al.  Flood boundary delineation from Synthetic Aperture Radar imagery using a statistical active contour model , 2001 .

[6]  Paul D. Bates,et al.  A new method for moving–boundary hydrodynamic problems in shallow water , 1999, Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences.

[7]  David C. Mason,et al.  Obtaining accurate maps of topography and vegetation to improve 2D hydraulic flood models , 2001, SPIE Remote Sensing.

[8]  Nicholas Kouwen,et al.  BIOMECHANICS OF VEGETATIVE CHANNEL LININGS , 1980 .

[9]  M. Horritt.  Calibration of a two‐dimensional finite element flood flow model using satellite radar imagery , 2000 .

[10]  V. T. Chow.  Open-channel hydraulics , 1959 .

[11]  P. Bates,et al.  INITIAL COMPARISON OF TWO TWO-DIMENSIONAL FINITE ELEMENT CODES FOR RIVER FLOOD SIMULATION. , 1995 .

[12]  Richard D. Hey,et al.  Flow Resistance in Gravel-Bed Rivers , 1979 .

[13]  H. Nepf.  Drag, turbulence, and diffusion in flow through emergent vegetation , 1999 .

[14]  Paul D. Bates,et al.  An initial comparison of two 2-D finite element codes for river flood simulation , 1995 .

[15]  David M. Cobby,et al.  Two‐dimensional hydraulic flood modelling using a finite‐element mesh decomposed according to vegetation and topographic features derived from airborne scanning laser altimetry , 2003 .

[16]  Stephen E. Darby,et al.  Effect of Riparian Vegetation on Flow Resistance and Flood Potential , 1999 .

[17]  Matthew S. Horritt,et al.  A statistical active contour model for SAR image segmentation , 1999, Image Vis. Comput..

[18]  W. I. Eastgate.  Vegetated stabilisation of grassed waterways and dam bywashes , 1967 .

[19]  S. Magnussen,et al.  Derivations of stand heights from airborne laser scanner data with canopy-based quantile estimators , 1998 .

[20]  M. Fathi-Maghadam,et al.  Nonrigid, Nonsubmerged, Vegetative Roughness on Floodplains , 1997 .

[21]  Fu‐Chun Wu,et al.  Variation of Roughness Coefficients for Unsubmerged and Submerged Vegetation , 1999 .

[22]  Robert N. Swift,et al.  Airborne Scanning Lidar Measurement of Ocean Waves , 2000 .

[23]  E. Næsset.  Determination of mean tree height of forest stands using airborne laser scanner data , 1997 .

[24]  Nicholas Kouwen,et al.  Field estimation of the biomechanical properties of grass , 1988 .

[25]  Andrea Defina,et al.  Two‐dimensional shallow flow equations for partially dry areas , 2000 .

[26]  Nicholas Kouwen,et al.  FLEXIBLE ROUGHNESS IN OPEN CHANNELS , 1973 .

[27]  P. Bates,et al.  Integration of high-resolution topographic data with floodplain flow models. , 2000 .

[28]  Nicholas Kouwen.  EFFECT OF RIPARIAN VEGETATION ON FLOW RESISTANCE AND FLOOD POTENTIAL. DISCUSSION , 2000 .

[29]  N. Kouwen,et al.  Friction Factors for Coniferous Trees along Rivers , 2000 .

[30]  M. S. Horritt,et al.  Development of physically based meshes for two‐dimensional models of meandering channel flow , 2000 .

[31]  Jerry C. Ritchie,et al.  Estimation of effective aerodynamic roughness of Walnut Gulch watershed with laser altimeter measurements , 1994 .

[32]  John R. Krebs,et al.  Improving bird population models using airborne remote sensing , 2000 .

[33]  Paul D Bates,et al.  Integrating remote sensing observations of flood hydrology and hydraulic modelling , 1997 .

[34]  Rhj Sellin,et al.  INTERNAL AND EXTERNAL VALIDATION OF A TWO-DIMENSIONAL FINITE ELEMENT CODE FOR RIVER FLOOD SIMULATIONS. , 1998 .

[35]  David C. Mason,et al.  Image processing of airborne scanning laser altimetry for some environmental applications , 1999, Remote Sensing.

[36]  Darrel M. Temple,et al.  Closure of "Velocity Distribution Coefficients for Grass-Lined Channels" , 1987 .

[37]  L. M Gomes Pereira,et al.  Suitability of laser data for deriving geographical information: A case study in the context of management of fluvial zones , 1999 .

[38]  Paul D. Bates,et al.  Development and testing of a subgrid-scale model for moving-boundary hydrodynamic problems in shallow water , 2000 .