source: production/onslow_2006/report/anuga.tex @ 3268

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1
2The software tool, ANUGA \cite{ON:modsim}, has been used to develop the
3inundation extent
4and associated water level at various points in space and time.
5ANUGA has been developed by GA and the Australian National University
6(ANU) to solve the nonlinear shallow water
7wave equation using the finite volume technique.
8An advantage of this technique is that the cell area can be changed
9according to areas of interest and that wetting and drying
10is treated robustly as part of the numerical scheme.
11ANUGA is continually being developed and validated to ensure
12the modelling approximations reflect new theory or
13available experimental data sets.
14As such, the current results represent ongoing work
15and may change in the future.
16
17The following set of information is required to undertake the
18inundation modelling;
19
20\begin{itemize}
21\item onshore and offshore elevation data (topographic and bathymetric data,
22see Section \ref{sec:data}),
23\item initial conditions, such as initial water levels (e.g. determined by tides),
24\item boundary condition (the tsunami source as described in
25Section \ref{sec:tsunamiscenario}),
26\item computational requirements relating to the mesh construction.
27\end{itemize}
28
29As part of the CRA, it was decided to provide results for the
30extremes of the tidal regimes to understand the potential range of impacts
31from the event. The Highest Astronomical Tide (HAT) and Lowest
32Astronomical Tide (LAT) are defined as 1.5m Australian Height Datum (AHD)
33and -1.5m AHD respectively for Onslow, \cite{antt:06}, with
34Mean Sea Level approximately equal to 0m AHD. These values are tidal
35predictions based on continous tidal observations from Standard Ports
36over a period of
37at least one year, with the Australian Hydrographic Service
38recommending this be extended to three years to capture
39changes to the mean sea level. Onslow is listed as
40a Standard Port. As an aside, current work at GA is
41extracting information from LANDSAT imagery to reconstruct the
42tidal variations for various WA locations. Future modelling of
43these areas will incorporate this information.
44
45
46The initial conditions used for this scenario is then MSL, HAT and LAT.
47The dynamics of
48tidal effects (that is, the changes in water height over time for
49the entire study area) is not currently modelled.
50Bottom friction will generally provide resistance to the water flow
51and thus reduce the impact somewhat. However, it is an open area
52of research on how to determine the friction coefficients, and
53thus it has not been incorporated
54in the scenario presented in this report. Therefore, the
55results presented are over estimated to some degree.
56
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