Wind Erosion in Western Queensland Australia

More documents

Recommendations

Info

Chapter 6 – Field Assessments and Model ValidationThe model output was then compared with visual assessments of land erodibility acquiredfrom 11 to 21 September 2006. The time difference between validation data collection andmodel simulations was unavoidable and dictated by access to the study area (September) andLandsat image acquisition dates (October). Evaluation of 5 x 5 km grass cover data from theAussieGRASS pasture growth model (Carter et al., 1996a,b) revealed that mean cover change(a net decrease) over the study area was ~2 % between 1 September and 30 October 2006, sothe effect of this time difference on the validation outcome is not believed to be significant.A point-to-pixel extraction method (ArcGIS 9.2, ESRI) was used to retrieve values frommodel output pixels coincident with the transect point observations (Figure 6.1). Modeloutput values were then plotted against the visual assessments of land erodibility. Thevalidation relies on a comparison of categorical (point observations) and continuous (modeloutput) data, so summary statistics (mean and standard deviation) of the model output werecomputed for each validation data class (highly erodible to not erodible). Model performancewas then evaluated by visual assessment of the distributions of predicted values across thevalidation data classes.6.4 Results and DiscussionFigure 6.4 presents plots of predicted versus observed land erodibility for the five outputscenes. For each scene the rate of change in the equation for the line of best fit can be used asa qualitative indicator of agreement in the data. For the Mt Dot, Bedourie and Cadell scenesthere is agreement in the data, with predicted and observed values increasing from low tohigh. The trend indicates that for the area covered by these scenes (Figure 6.1) AUSLEMcaptures the susceptibility of the landscape to wind erosion. There is a weak positive trend inthe data for the Windorah scene. Data for the Quilpie scene shows poor agreement betweenpredicted and observed values. Here the model over-predicts land erodibility for the lowerodibility class and consistently under-predicts across the moderate and high classes.The variability in predicted land erodibility values for each observation class differs betweenthe classes and output scenes (Figure 6.4). There is significant overlap in the modelpredictions between observation classes, and this was expected in comparing the continuous164
Chapter 6 – Field Assessments and Model Validationand categorical data. Two factors affect the class separation and this complicates assessmentsof model performance.Figure 6.4 Modelled versus observed land erodibility for the five Landsat scenes. The data show themean ± 1 standard deviation (SD) of the predicted values for each observed land erodibility class. Thenumber of observations (n) is shown for each class.Firstly, the scale in the model output is non-linear, increasing exponentially between 0 and 1.This non-linearity is driven by a high sensitivity of the model (and wind erosion) to small165
Page 1:
Modelling Land Susceptibility toWin
Page 4:
AUSLEM was developed as a Geographi
Page 8 and 9:
who joined me on many trips, shared
Page 10 and 11:
Conference Presentations by the Aut
Page 12 and 13:
2.2.5 Soil Moisture Effects........
Page 14 and 15:
Chapter 6: Assessing Land Susceptib
Page 16 and 17:
List of FiguresChapter 1: Introduct
Page 18 and 19:
Figure 2.11 Conceptual model of lan
Page 20 and 21:
hand column) presents trajectories
Page 22 and 23:
List of TablesChapter 1: Introducti
Page 24 and 25:
xxii
Page 26 and 27:
Chapter 1 - Introduction• The abi
Page 28 and 29:
Chapter 1 - Introductionchapter the
Page 30 and 31:
Chapter 1 - Introductionevents yr -
Page 32 and 33:
Chapter 1 - IntroductionFigure 1.2
Page 34 and 35:
Chapter 1 - Introductionsusceptibil
Page 36 and 37:
Chapter 1 - Introductiontemporal pa
Page 38 and 39:
Chapter 1 - Introduction1.5 Researc
Page 40 and 41:
Chapter 1 - IntroductionFigure 1.3
Page 42 and 43:
Chapter 1 - IntroductionMitchell Gr
Page 44 and 45:
Chapter 1 - IntroductionSimpson-Str
Page 46 and 47:
Chapter 1 - IntroductionDowns. Wind
Page 48 and 49:
Chapter 1 - IntroductionChapter 2 p
Page 50 and 51:
Chapter 2 - Land Erodibility Contro
Page 52 and 53:
Page 54 and 55:
Page 56 and 57:
Page 58 and 59:
Page 60 and 61:
Page 62 and 63:
Page 64 and 65:
Page 66 and 67:
Page 68 and 69:
Page 70 and 71:
Page 72 and 73:
Page 74 and 75:
Page 76 and 77:
Page 78 and 79:
Page 80 and 81:
Page 82 and 83:
Page 84 and 85:
Page 86 and 87:
Page 88 and 89:
Page 90 and 91:
Page 93 and 94:
Chapter 3 - Modelling Land Erodibil
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121:
Page 124 and 125:
Chapter 4 -Modelling Soil Erodibili
Page 126 and 127:
Page 128 and 129:
Page 130 and 131:
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
Page 138 and 139: Chapter 4 -Modelling Soil Erodibili
Page 154 and 155: Chapter 5 - Land Erodibility Model
Page 182 and 183: Chapter 6 - Field Assessments and M
Page 192 and 193: Chapter 7 - Land Erodibility Dynami
Page 214 and 215: Chapter 8 - Conclusions• There is
Page 216 and 217: Chapter 8 - ConclusionsThe third ai
Page 218 and 219: Chapter 8 - Conclusionswas shown to
Page 220 and 221: Chapter 8 - Conclusionsland use cha
Page 222 and 223: Chapter 8 - Conclusionsmodels are n
Page 224 and 225: Chapter 8 - Conclusionsmultiple ass
Page 226 and 227: Chapter 8 - Conclusionsthe opportun
Page 228 and 229: Beadle, N.C.W., 1945. Dust storms.
Page 230 and 231: Bryan, R.B., Govers, G., Poesen, J.
Page 232 and 233: Chepil, W.S., 1965. Transport of so
Page 234 and 235: Fryrear, D.W., Sutherland, P.L., Da
Page 236 and 237: Gregory, J.M., 1984. Prediction of
Page 238 and 239:
Hugenholtz, C.H., Wolfe, S.A., 2005
Page 240 and 241:
Littleboy, M., McKeon, G.M., 1997.
Page 242 and 243:
Marshall, J.K., 1973. Drought, land
Page 244 and 245:
Assessment Report of the Intergover
Page 246 and 247:
Penner, J.E., et al. , 2001. Climat
Page 248 and 249:
Rickert, K.G., McKeon, G.M., 1982.
Page 250 and 251:
Stokes, C., J., McAllister, R.R.J.,
Page 252 and 253:
Williams, W.J., Eldridge, D.J., Alc
show all

Wind Erosion in Western Queensland Australia

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?