source: production/onslow_2006/report/anuga.tex @ 3219

The software tool, ANUGA \cite{ON:modsim}, has been used to develop the 
inundation extent
and associated water level at various points in space and time.
ANUGA has been developed by GA and the Australian National University
(ANU) to solve the nonlinear shallow water
wave equation using the finite volume technique.
An advantage of this technique is that the cell area can be changed
according to areas of interest and that wetting and drying
is treated robustly as part of the numerical scheme. 
ANUGA is continually being developed and validated.
As such, the current results represent ongoing work
and may change in the future.

The following set of information is required to undertake the 
inundation modelling;

\begin{itemize}
\item onshore and offshore elevation data (topographic and bathymetric data, 
see Section \ref{sec:data})
\item initial conditions, such as initial water levels (e.g. determined by tides)
\item boundary condition (the tsunami source as described in 
Section \ref{sec:tsunamiscenario})
\item forcing terms (such as wind)
\item computational requirements relating to the mesh construction
\end{itemize}

As part of the CRA, it was decided to provide results for the
extremes of the tidal regimes to understand the potential range of impacts 
from the event. Onslow is termed a Standard Port
by the Australian Hydrographic Service, with tidal
predictions based on continuous observation of the tide
over a period of at least one year, however it is advised that these
observations extend to three years to note changes in the mean
sea level. The Australian National Tide Tables 2006 \cite{antt:06}
describes how
these predictions are rounded to two decimal places, then
further rounded to a single decimal place. 
Figure \ref{fig:ic} shows the contour lines for
the values for
Highest Astronomical Tide (HAT; 1.5m AHD), Mean Sea Level (MSL; 0m AHD) 
and Lowest Astronomical Tide (LAT; -1.5m AHD) for Onslow, \cite{antt:06}.
It is evident from this figure that significant areas of Onslow are
inundated before the simulation is even begun indicating 
shortcomings with the underlying data set. Therefore, we use only
one initial condition for this scenario; 0m AHD. Further
discussion surrounding the data and its sources is described in
Sections \ref{sec:data} and \ref{sec:metadata}.
%It is important to note that there is no Bureau of Metereoolgy
%tide gauge in Onslow, 
As an aside, a current GA contract is
extracting information from LANDSAT imagery to reconstruct the 
tidal variations for various WA locations. Future modelling of
these areas will incorporate this information.
Further, the dynamics of
tidal effects (that is, the changes in water height over time for
the entire study area) is not currently modelled.
%In the simulations provided in this report, we assume that 
%increase of water height for the initial condition is spatially consistent
%for the study region. 
Bottom friction will generally provide resistance to the water flow
and thus reduce the impact somewhat. However, it is an open area
of research on how to determine the friction coefficients, and 
thus it has not been incorporated
in the scenarios presented in this report. Therefore, the 
results presented are over estimated to some degree.

\begin{figure}[hbt]

  \centerline{ \includegraphics[width=150mm, height=100mm]
{../report_figures/contours.jpg}}

  \caption{Onslow regions showing the 1.5m AHD, 0m AHD and -1.5m AHD contour lines.}
  \label{fig:ic}
\end{figure}