source: production/onslow_2006/report/discussion.tex @ 3235

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. The Highest Astronomical Tide (HAT) and Lowest
Astronomical Tide (LAT) are defined as 1.5m AHD and -1.5m AHD 
respectively for Onslow, \cite{antt:06}. These values are tidal
predictions based on continous tidal observations from Standard Ports
over a period of
at least one year, with the Australian Hydrographic Service
recommending this be extended to three years to capture
changes to the mean sea level. Onslow is listed as
a Standard Port. These predictions are ultimately rounded on a single
decimal place.

Figure \ref{fig:contours} shows the contour lines for
the HAT, MSL and LAT for Onslow.
It is evident from this figure that the extent of the tidal
inundation is exaggerated which is due to
short comings with the digital elevation model (DEM). The DEM has been 
derived from 20m contour lines. {\bf Need some words from hamish here.}

As an aside, current work at GA is
extracting information from LANDSAT imagery to reconstruct the 
tidal variations for various WA locations. Future modelling of
these areas will incorporate this information.

\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:contours}
\end{figure}