Modelling Channelling and Deflection of Wind by Topography

Topographic indices have been used extensively in the past to model wind-related phenomena such as soil erosion, snow redistribution, and atmospheric deposition of contaminants. A new index of exposure/sheltering to wind, the channelling/deflection index (CDI), is presented and evaluated in this chapter. Unlike existing windiness indices, most of which are based on ray-tracing algorithms, the CDI is capable of modelling channelling and deflection of flowlines, as well as wind shadowing. The CDI is a measure of how much more or less windy a location is as a result of the influence of upwind topography. The method for calculating the CDI applies a flow routing algorithm to model airflow patterns. Like all topographic indices involving the analysis of extended neighbourhoods, the CDI is affected by edge contamination; the location of digital elevation model (DEM) edges can significantly influence the CDI pattern estimated for an area. Analyses showed that edge effects can be diminished by using an appropriately sized buffer of elevation data in the windward direction. A 4 km buffer was found to be sufficient to accurately model the CDI in five study areas of varying topography, based on DEM data with a 10 m grid resolution.

[1]  K. Schulz,et al.  Spatial extrapolation of agrometeorological variables , 1999 .

[2]  A. Chappell.  Modelling the spatial variation of processes in the redistribution of soil: digital terrain models and 137Cs in southwest Niger , 1996 .

[3]  Prediction method for surface wind velocity distribution by means of regression analysis of topographic effects on local wind speed , 1983 .

[4]  T. Legovic,et al.  Estimating the direction of an unknown air pollution source using a digital elevation model and a sample of deposition , 1999 .

[5]  M. Shirasawa,et al.  Visualizing topography by openness: A new application of image processing to digital elevation models , 2002 .

[6]  Frédéric Darboux,et al.  A fast, simple and versatile algorithm to fill the depressions of digital elevation models , 2002 .

[7]  John F. O'Callaghan,et al.  The extraction of drainage networks from digital elevation data , 1984, Comput. Vis. Graph. Image Process..

[8]  John B. Lindsay,et al.  The Terrain Analysis System: a tool for hydro‐geomorphic applications , 2005 .

[9]  C. P. Quine,et al.  Using the Relationship between Rate of Tatter and Topographic Variables to Predict Site Windiness in Upland Britain , 1994 .

[10]  John P. Wilson,et al.  Terrain analysis : principles and applications , 2000 .

[11]  I. Moore,et al.  Digital terrain modelling: A review of hydrological, geomorphological, and biological applications , 1991 .

[12]  K. Beven,et al.  THE PREDICTION OF HILLSLOPE FLOW PATHS FOR DISTRIBUTED HYDROLOGICAL MODELLING USING DIGITAL TERRAIN MODELS , 1991 .

[13]  D. Tarboton.  A new method for the determination of flow directions and upslope areas in grid digital elevation models , 1997 .

[14]  Danny Marks,et al.  Simulating wind fields and snow redistribution using terrain‐based parameters to model snow accumulation and melt over a semi‐arid mountain catchment , 2002 .

[15]  John B. Lindsay.  A physically based model for calculating contributing area on hillslopes and along valley bottoms , 2003 .

[16]  Vivette Girault,et al.  Finite Element Methods for Navier-Stokes Equations - Theory and Algorithms , 1986, Springer Series in Computational Mathematics.

[17]  Kelly Elder,et al.  Spatial Snow Modeling of Wind-Redistributed Snow Using Terrain-Based Parameters , 2002 .

[18]  Takanori Uchida,et al.  Numerical simulation of atmospheric flow over complex terrain , 1999 .

[19]  Gregory J. McCabe,et al.  Comparison of Single and Multiple Flow Direction Algorithms for Computing Topographic Parameters in TOPMODEL , 1995 .

[20]  S. K. Jenson,et al.  Extracting topographic structure from digital elevation data for geographic information-system analysis , 1988 .

[21]  R. Peckham,et al.  Digital Terrain Modelling , 2007 .

[22]  J. Dozier,et al.  A faster solution to the horizon problem , 1981 .

[23]  M. Costa-Cabral,et al.  Digital Elevation Model Networks (DEMON): A model of flow over hillslopes for computation of contributing and dispersal areas , 1994 .

[24]  J. Lindsay,et al.  Removal of artifact depressions from digital elevation models: towards a minimum impact approach , 2005 .

[25]  K.-Y. Huang.  Evaluation of the topographic sheltering effects on the spatial pattern of Taiwan fir using aerial photography and GIS , 2002 .

[26]  T. G. Freeman,et al.  Calculating catchment area with divergent flow based on a regular grid , 1991 .

[27]  M. Hutchinson,et al.  Digital terrain analysis. , 2008 .

[28]  T. Erickson,et al.  Persistence of topographic controls on the spatial distribution of snow in rugged mountain terrain, Colorado, United States , 2005 .

[29]  Lawrence W. Martz,et al.  The measurement of two simple topographic indices of wind sheltering-exposure from raster digital elevation models , 1993 .