Windthrow Hazard Mapping using GIS, Canadian Forest Products ...

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Exploration of independent variables: range and means of x-variablesThe means and other statistics of some important variables are shown in Table 5. It isimportant to note that the models generated with this dataset will work best forlocations whose attributes fall within these limits.Table 5. Table of variables with some vital statistics (n = 22,106).Variable Label Mean Std Dev Minimum MaximumAge (yrs) AGE 141 64 0 400Aspect ( o ) ASP100 175 98 0 360Elevation (m) ELV100 726 258 0 1201Height (m) HEIGHT 25 11 0 44Mean wind speed (m/s) MWSPEED 4 1 3 6Crown closure CC_TREE 34 18 0 80Slope ( o ) SLP100 10 10 0 95Topex100_1000m ( o ) TPX100_1k 22 20 -64 169Max wind moderate event (m/s) MODMAXS 8 2 3 12Max wind strong event (m/s) STRMAXS 12 2 7 21Volume conifers (m 3 ) VOLC 271 172 0 1087Correlation between selected variablesThe correlations between independent variables were generally weak. Elevation ispositively correlated with mean windspeed and with slope. The stand variables height,age and volume are correlated as expected. Mean wind speed is weakly correlatedwith topex. Peak winds are weakly inversely correlated with elevation (Table 6).Table 6. A table of correlation between selected independent variables (n=22,077).Variable 1 Variable 2 CorrelationcoefficientELEV SLOPE 0.43ELEV MWSPEED 0.84ELEV MODMAXS -0.31ELEV STRMAXS -0.36ELEV TOPEX3K 0.24TOPEX3K MWSPEED 0.42TOPEX3K MODMAXS -0.53TOPEX3K STRMAXS -0.02MWSPEED MODMAXS -0.38MWSPEED STRMAXS -0.18MODMAXS STRMAXS -0.02FUNNELNS STRMAXS 0.02FUNNELEW STRMAXS -0.10CBRGCN CBRGP 0.55SCORE DIREX 0.36HEIGHT AGE 0.89HEIGHT VOLC 0.8010
Contingency tablesTrends in the proportion of segments damaged relative to class values of independentvariables are shown in Figure 2. Damage frequency increased with increasing meanannual windspeed and with increasing peak wind speed during a strong wind event,with number of directions of boundary exposure, with stand height and basal area, andwith time since logging. Damage frequency declined with decreasing topographicexposure and ground slope. Damage frequency is highest for south facing segmentsand when the cutblock centroid is south or west of the segments. Segments located onslopes with east aspects were less frequently damaged than those on other aspects.Stands dominated by hardwoods, subalpine fir and redcedar were less frequentlydamaged than those dominated by Douglas-fir, hemlock, lodgepole pine and spruce.There are no strong relationships between damage frequency and elevation, oropening width. In the latter case, most of the openings are much larger than the 5 treelengths at which sheltering effects from the leading stand edge have been observed inother studies.a)b)%60504030201003.5 4.5 5.5 6.5120001000080006000400020000#%201510500 25 50 75 100125 15014000120001000080006000400020000#MeanWSTopex 2kmc)d)%2015105070006000500040003000200010000#%20151050150001000050000#650 750 850 950 105011505 15 25 35 45 55ElevationBasal Area11
Page 3 and 4: models have been successfully devel
Page 5 and 6: angle between peak wind direction a
Page 7 and 8: Determination of independent variab
Page 9: anking of risk groups. For practica
Page 13 and 14: k)l)0.2060001612000Proportion0.150.
Page 15 and 16: Observed0.450.40.350.30.250.20.150.
Page 17 and 18: was not possible to evaluate this e
Page 19 and 20: ReferencesAnderson, C. J., Coutts,
Page 21 and 22: Appendix 1. Procedures used to buil
Page 23 and 24: Table A1-3. Map formulas used to ca
Page 25: *a pdf version of this map is attac

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