1 | The following information is required to undertake the |
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2 | inundation modelling; |
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3 | |
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4 | \begin{itemize} |
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5 | \item onshore and offshore elevation data (topographic and bathymetric data, |
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6 | see Section \ref{sec:data}), |
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7 | \item initial conditions, such as initial water levels (e.g. determined by tides) and the tsunami source |
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8 | as described in Section \ref{sec:methodology}, |
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9 | \item boundary conditions and |
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10 | \item computational requirements relating to the mesh construction. |
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11 | \end{itemize} |
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12 | |
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13 | Here, we choose the inital tidal levels to be MSL, i.e. 0m AHD. |
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14 | The dynamics of |
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15 | tidal effects (that is, the changes in water height over time for |
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16 | the entire study area) are not currently modelled. |
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17 | |
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18 | To set up a model for the tsunami scenario, a study area is first determined. |
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19 | The finite volume technique relies on the construction of a triangular mesh which covers the study region. |
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20 | This mesh can be altered to suit the needs of the scenario in question. The mesh can be refined in areas of |
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21 | interest, particularly in the coastal region where complex behaviour is likely to occur. For the purpose |
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22 | of this study, we will refine the mesh around the major population centres and adjoining coastlines. |
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23 | In setting up the model, the user defines the area of the triangular cells in each region of interest\footnote{Note that the cell |
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24 | area will be the maximum cell area within the defined region and that each |
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25 | cell in the region does not necessarily have the same area.}. |
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26 | |
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27 | Figures \ref{fig:regionA}, \ref{fig:regionB} and \ref{fig:regionC} show the study areas with regions |
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28 | of different cell areas for regions A, B and C |
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29 | respectively. The study areas have been defined where data |
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30 | is available. The total number of cells are 395403, 499816, 518362 and for regions A, B and C respectively. |
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31 | Each study area approximately centres the slide origin and extends approximately 50 - 100 km east of each origin. Typically, |
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32 | the region |
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33 | extends offshore to around the 3000-4000m depth contour with the onshore data covering the |
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34 | area of interest. Typical models do not extend to these depths, however, the extent has been increased |
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35 | to ensure the surface elevation function generated for the slide failure is captured in the domain. |
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36 | The study areas are approximately 19000 km$^2$, 10350 km$^2$ and 20900 km$^2$ |
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37 | for regions A, B and C respectively. |
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38 | Lateral accuracy refers to the distance at which we are confident in stating a region is inundated. |
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39 | Figures \ref{fig:regionA}, \ref{fig:regionB} and \ref{fig:regionC} show |
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40 | the maximum triangular cell area and lateral accuracy for each region. |
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41 | Therefore we can only be confident in the calculated inundation extent surrounding major populations centres to within 30 m. |
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42 | |
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43 | \begin{figure}[hbt] |
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44 | |
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45 | \centerline{ \includegraphics[scale=0.5]{../report_figures/regionAmodel.jpg}} |
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46 | |
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47 | \caption{Study area for region A highlighting four regions of increased refinement. |
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48 | Region 1: Surrounding major population centre of Wollongong with a cell area of 500 m$^2$ (lateral accuracy 30 m). |
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49 | Region 2: Surrounding Lake Illawarra (south of Wollongong) with a cell area of 500 m$^2$ (lateral accuracy 30 m). |
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50 | Region 3: Surrounds the coastal regions with a cell area of 25000 m$^2$ (lateral accuracy 220 m). |
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51 | Region 4: The remaining area is given a cell area of 1000000 m$^2$ (lateral accuracy 1400 m). |
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52 | } |
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53 | \label{fig:regionA} |
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54 | \end{figure} |
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55 | |
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56 | \begin{figure}[hbt] |
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57 | |
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58 | \centerline{ \includegraphics[scale=0.5]{../report_figures/regionBmodel.jpg}} |
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59 | |
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60 | \caption{Study area for region B highlighting three regions of increased refinement. |
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61 | Region 1: Surrounding the entrance to Sydney harbour, Northern Beaches and Botany Bay with a cell area of 500 m$^2$ (lateral accuracy 30 m). |
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62 | Region 2: Surrounding the coastal regions with a cell area of 50000 m$^2$ (lateral accuracy 315 m). |
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63 | Region 3: The remaining area is given a cell area of 250000 m$^2$ (lateral accuracy 700 m). |
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64 | } |
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65 | \label{fig:regionB} |
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66 | \end{figure} |
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67 | |
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68 | \begin{figure}[hbt] |
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69 | |
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70 | \centerline{ \includegraphics[scale=0.5]{../report_figures/regionCmodel.jpg}} |
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71 | |
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72 | \caption{Study area for region C highlighting three regions of increased refinement. |
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73 | Region 1: Surrounding the major population centre of Newcastle with a cell area of 1000 m$^2$ (lateral accuracy 45 m). |
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74 | Region 2: Surrounding the coastal regions with a cell area of 50000 m$^2$ (lateral accuracy 315 m). |
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75 | Region 3: The remaining area is given a cell area of 500000 m$^2$ (lateral accuracy 1000 m). |
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76 | } |
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77 | \label{fig:regionC} |
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78 | \end{figure} |
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79 | |
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80 | The final item to be addressed to complete the model setup is the |
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81 | definition of the boundary condition. The tsunami source in this |
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82 | study is given as an initial condition, as opposed to a boundary |
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83 | condition to studies when the tsunami is generated by an undersea |
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84 | earthquake. Hence, the boundary conditions for this model will |
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85 | be Dirichlet boundary conditions, that is, all quantities are |
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86 | given constant values. Here, stage and velocity at the boundaries |
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87 | are set to 0. |
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88 | |
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89 | Sea floor friction will generally provide resistance to the water flow |
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90 | and thus reduce the impact somewhat. However, limited |
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91 | research has been carried out to determine |
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92 | the friction coefficients, and |
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93 | thus it has not been incorporated |
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94 | in the scenario. The |
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95 | results are therefore likely to be over estimates. |
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96 | |
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97 | The following table summarises the other modelling parameters; |
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98 | |
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99 | |
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100 | \begin{table} |
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101 | \begin{center} |
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102 | |
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103 | \caption{Parameters used in ANUGA for the the submarine mass failure scenarios.} |
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104 | \begin{tabular}{|l|l|}\hline |
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105 | Model parameters & Value \\ \hline |
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106 | friction & 0 \\ \hline |
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107 | minimum stored height & 0.1 m \\ \hline |
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108 | \end{tabular} |
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109 | |
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110 | \end{center} |
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111 | \end{table} |
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112 | |
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113 | |
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114 | \begin{table} |
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115 | \begin{center} |
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116 | |
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117 | \caption{Output directories for model simulations.} |
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118 | \begin{tabular}{|l|l|l|}\hline |
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119 | {\bf Region} & {\bf Slide} & {\bf Location:} |
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120 | $\backslash {\rm inundation \backslash data \backslash new\_south\_wales |
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121 | \backslash }$ \\ \hline |
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122 | A & Bulli - Historical & $ {\rm wollongong \_tsunami\_scenario\_2006 \backslash anuga |
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123 | \backslash outputs \backslash 20070213\_035110}$ \\ \hline |
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124 | A & Shovel - Historical & ${\rm wollongong \_tsunami\_scenario\_2006 \backslash anuga |
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125 | \backslash outputs \backslash |
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126 | 20070213\_035146}$ \\ \hline |
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127 | A & Yacaaba & ${\rm wollongong \_tsunami\_scenario\_2006 \backslash anuga |
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128 | \backslash outputs \backslash |
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129 | 20070213\_035302}$ \\ \hline |
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130 | B & Bulli & ${\rm sydney \_tsunami\_scenario\_2006 \backslash anuga |
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131 | \backslash outputs \backslash |
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132 | 20070213\_033012}$ \\ \hline |
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133 | B & Shovel & ${\rm sydney \_tsunami\_scenario\_2006 \backslash anuga |
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134 | \backslash outputs \backslash |
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135 | 20070213\_031322}$ \\ \hline |
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136 | B & Yacaaba & $\rm{ sydney \_tsunami\_scenario\_2006 \backslash anuga |
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137 | \backslash outputs \backslash |
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138 | 20070213\_033058}$ \\ \hline |
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139 | C & Bulli & ${\rm newcastle \_tsunami\_scenario\_2006 \backslash anuga |
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140 | \backslash outputs \backslash |
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141 | 20070219\_060722}$ \\ \hline |
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142 | C & Shovel & ${\rm newcastle \_tsunami\_scenario\_2006 \backslash anuga |
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143 | \backslash outputs \backslash |
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144 | 20070219\_060808}$ \\ \hline |
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145 | C & Yacaaba - Historical & ${\rm newcastle \_tsunami\_scenario\_2006 \backslash anuga |
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146 | \backslash outputs \backslash |
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147 | 20070219\_060854}$ \\ \hline |
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148 | \end{tabular} |
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149 | |
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150 | \end{center} |
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151 | \end{table} |
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