source: anuga_work/production/sydney_2006/report/anuga_setup.tex @ 4090

Last change on this file since 4090 was 4090, checked in by sexton, 17 years ago

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1The following information is required to undertake the
2inundation modelling;
3
4\begin{itemize}
5\item onshore and offshore elevation data (topographic and bathymetric data,
6see Section \ref{sec:data}),
7\item initial conditions, such as initial water levels (e.g. determined by tides),
8\item boundary conditions (the tsunami source as described in
9Section \ref{sec:methodology}), and
10\item computational requirements relating to the mesh construction.
11\end{itemize}
12 
13Here, we choose the inital tidal levels to be MSL, i.e. 0m AHD.
14The dynamics of
15tidal effects (that is, the changes in water height over time for
16the entire study area) are not currently modelled.
17
18To set up a model for the tsunami scenario, a study area is first determined.
19The finite volume technique relies on the construction of a triangular mesh which covers the study region.
20This mesh can be altered to suit the needs of the scenario in question. The mesh can be refined in areas of
21interest, particularly in the coastal region where complex behaviour is likely to occur. For the purpose
22of this study, we will refine the mesh around the major population centres and adjoining coastlines.
23In setting up the model, the user defines the area of the triangular cells in each region of interest\footnote{Note that the cell
24area will be the maximum cell area within the defined region and that each
25cell in the region does not necessarily have the same area.}.
26
27Figures \ref{fig:regionA}, \ref{fig:regionB} and \ref{fig:regionC} show the study areas with regions
28of different cell areas for regions A, B and C
29respectively. The study areas have been defined where data
30is available. The total number of cells are 395403, 499816, 518362 and for regions A, B and C respectively.
31Each study area approximately centres the slide origin and extends approximately 50 - 100 km east of each origin. Typically,
32the region 
33extends offshore to around the 3000-4000m depth contour with the onshore data covering the
34area of interest. Typical models do not extend to these depths, however, the extent has been increased
35to ensure the surface elevation function generated for the slide failure is captured in the domain.
36The study areas are approximately 19000 km$^2$, 10350 km$^2$ and 20900 km$^2$ 
37for regions A, B and C respectively.
38Lateral accuracy refers to the distance at which we are confident in stating a region is inundated.
39Figures \ref{fig:regionA}, \ref{fig:regionB} and \ref{fig:regionC} show
40the maximum triangular cell area and lateral accuracy for each region.
41Therefore we can only be confident in the calculated inundation extent surrounding major populations centres to within 30 m.
42
43\begin{figure}[hbt]
44
45  %\centerline{ \includegraphics[scale=0.5]{../report_figures/regionA_model.jpg}}
46
47  \caption{Study area for region A highlighting four regions of increased refinement.
48Region 1: Surrounding major population centre of Wollongong with a cell area of 500 m$^2$ (lateral accuracy 30 m).
49Region 2: Surrounding Lake Illawarra (south of Wollongong) with a cell area of 500 m$^2$ (lateral accuracy 30 m).
50Region 3: Surrounds the coastal regions with a cell area of 25000 m$^2$ (lateral accuracy  m).
51Region 4: The remaining area is given a cell area of 1000000 m$^2$ (lateral accuracy  m).
52}
53  \label{fig:regionA}
54\end{figure}
55
56\begin{figure}[hbt]
57
58  %\centerline{ \includegraphics[scale=0.5]{../report_figures/regionB_model.jpg}}
59
60  \caption{Study area for region B highlighting four regions of increased refinement.
61Region 1: Surrounding the entrance to Sydney harbour, Northern Beaches and Botany Bay with a cell area of 500 m$^2$ (lateral accuracy 30 m).
62Region 2: Surrounding the coastal regions with a cell area of 50000 m$^2$ (lateral accuracy m).
63Region 3: The remaining area is given a cell area of 250000 m$^2$ (lateral accuracy m).
64}
65  \label{fig:regionB}
66\end{figure}
67
68\begin{figure}[hbt]
69
70  %\centerline{ \includegraphics[scale=0.5]{../report_figures/regionC_model.jpg}}
71
72  \caption{Study area for region C highlighting four regions of increased refinement.
73Region 1: Surrounding the major population centre of Newcastle with a cell area of 1000 m$^2$ (lateral accuracy m).
74Region 2: Surrounding the coastal regions with a cell area of 50000 m$^2$ (lateral accuracy  m).
75Region 3: The remaining area is given a cell area of 500000 m$^2$ (lateral accuracy  m).
76}
77  \label{fig:regionC}
78\end{figure}
79
80The final item to be addressed to complete the model setup is the
81definition of the boundary condition. As
82discussed in Section \ref{sec:methodology}, a Mw 9 event provides
83the tsunami source. The resultant tsunami wave is made up of a series
84of waves with different amplitudes which is affected by the energy
85and style of the event as well as the bathymetry whilst it travels
86from its source to Dampier. The amplitude and velocity of each of these
87waves are then provided to ANUGA as boundary conditions and propagated
88inshore.
89
90Sea floor friction will generally provide resistance to the water flow
91and thus reduce the impact somewhat. However, limited
92research has been carried out to determine
93the friction coefficients, and
94thus it has not been incorporated
95in the scenario. The
96results are therefore likely to be over estimates.
97
98The following table summarises the other modelling parameters;
99
100
101\begin{table}
102\begin{center}
103
104\caption{Parameters used in ANUGA for the the submarine mass failure scenarios.}
105\begin{tabular}{|l|l|}\hline
106Model parameters  & Value \hline
107friction & 0
108minimum stored height & 0.1 m \hline
109\end{tabular}
110
111\end{center}
112\end{table}
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