To initiate the modelling, the computational mesh is constructed to
cover the available data. The resolution is chosen to balance
computational time and desired resolution in areas of interest,
particularly in the interface between the on and offshore. The
following figure illustrates the data extent for the 
scenario and where further mesh refinement has been made. The choice
of the refinement is based around the important inter-tidal zones and
other important features such as islands and rivers. The most northern
boundary of the study area is placed approximately around the 100m contour
line. 
The resultant computational mesh is then seen in figure \ref{fig:mesh_onslow}.

\begin{figure}[hbt]

  \centerline{ \includegraphics[width=100mm, height=75mm]{../report_figures/onslow_data_poly.png}}

  \caption{Study area for Onslow scenario highlighting areas of increased refinement.}
  \label{fig:onslow_area}
\end{figure}


\begin{figure}[hbt]

  %\centerline{ \includegraphics[width=100mm, height=75mm]{../report_figures/.png}}

  \caption{Computational mesh for Onslow study area}
  \label{fig:mesh_onslow}
\end{figure}

For the simulations, we have chosen a resolution of 500 m$^2$ for the 
region surrounding the Onslow town centre. The resolution is increased 
to 2500 m$^2$ for the region surrounding the coast and further increased
to 20000 m$^2$ for the region reaching approximately the 50m contour line.
The remainder of the study area has a resolution of 100000 m$^2$. 
With these resolutions in place, the study area consists of 440150 triangles. 
The associated accuracy 
for these resolutions is approximatly 22m, 50m, 140m and 315m for the increasing
resolutions. This means
that we can only be confident in the calculated inundation to approximately
22m accuracy within the Onslow town centre. 
This is because ANUGA calculates whether each cell in the triangular
mesh is wet or dry. It is important
to refine the mesh to be commensurate with the underlying data especially in 
those regions where complex behaviour will occur, such as the inter-tidal
zone and estuaries. 
