source: production/pt_hedland_2006/report/interpretation.tex @ 3383

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[3364]1The main features of the
2tsunami wave and resultant impact ashore is described in this section.
3We have
[3375]4chosen a number of locations which we believe would be critical
5in an emergency situation, such as the hospital and power station; or
[3364]6effect recovery efforts, such as the airport and docks. These locations
7are described in Table \ref{table:locations} and shown in
8Figure \ref{fig:points}. The water's stage and speed are shown
9as a function of time in the series of graphs shown in
10Appendix \ref{sec:timeseries}. Stage is defined as the absolute
11water level relative to AHD. Both stage and speed are shown
12on consistent scales to allow comparison between point locations.
13%The graphs show these time series for
14%the three cases; 1.5m AHD, 0m AHD and -1.5m AHD so that comparisons can
15%be made.
16As a useful benchmark, Table \ref{table:speedexamples}
[3015]17describes typical examples for a range of velocities found in the
18simulations.
19
20\begin{table}
[3364]21\begin{center}
[3015]22\caption{Examples of a range of velocities.}
[3364]23\label{table:speedexamples}
[3015]24\begin{tabular}{|l|l|}\hline
[3364]25{\bf Velocity (m/s)} & {\bf Example} \\ \hline
[3015]261 & leisurely stroll pace\\ \hline
271.5 & average walking pace \\ \hline
[3364]28%2 & 100m Olympic male freestyle \\ \hline
29%3 & mackeral \\ \hline
[3375]304 & average person can maintain running for 1000m \\ \hline
[3364]31%5 & blue whale \\ \hline
[3015]3210 & 100m Olympic male sprinter \\ \hline
3316 & car travelling in urban zones (60 km/hr) \\ \hline
34\end{tabular}
35\end{center}
36\end{table}
37
[3380]38{\bf this needs to reflect what happens for port hedland}
39
[3364]40Examining the offshore locations shown in Appendix
41\ref{sec:timeseries}, the drawdown prior to the tsunami wave
[3015]42arriving at the shore can be seen to occur around 230 mins 
43(3.8 hours) after the tsunami is generated.
[3364]44Prior to the drawdown, maximum amplitudes are approximately 50cm at
45West of Groyne (Figure ) and
46the mouth of Beadon Creek
47(Figure ), for example.
48The first wave
49after the drawdown ranges from approximately 2m in the
50west of Beadon Bay (Figure )
51to over 3m in the mouth of Beadon Creek
52(Figure ).
53The speed
[3015]54sharply increases at drawdown with further increases as the
55wave grows in amplitude.
[3364]56There is an increased amplitude of approximately 4m found in
[3015]57east of Beadon Bay for the secondary wave, as opposed to the first wave.
[3364]58This feature is also evident at the West of Groyne location but
59with decreased amplitude.
[3015]60This may be due to the geography of the bay, including the groyne west of
61the creek mouth opening, the local bathymetry
62and the direction of the tsunami wave.
63
[3364]64The maximum speed found for the offshore locations occur at the West of
65Groyne location (Figure ).
66The speeds at west and east of Beadon Bay are quite similar
[3373]67(Figure and Figure ).
[3364]68However, there are increased amplitudes (from drawdown to maximum
69amplitude), in the eastern location which is in shallower water than the western
70location.
[3015]71Subsequent drawdowns are seen as the multitude of waves which make up the
72event propagate towards the shore.
73
74%At some gauge locations, these
75%subsequent waves cause significantly increased inundation than that of
76%the first wave. This is particularly seen at the Beadon Creek Docks,
77%West of Groyne and Beadon Creek locations.
78
[3364]79It is evident that the sand dunes west of
80Port Hedland are very effective in halting the tsunami wave,
81see Figure \ref{fig:MSL_max_inundation}.
82There is inundation between the western sand dunes at high
83tide, Figure \ref{fig:HAT_max_inundation}, however, this water
84penetrates from the north east (via
85Port Hedland town centre) rather than seaward. (The DEM indicates that
86this area is under 1.5m AHD which is automatically deemed to be inundated
87at HAT.)
88The same feature is evident for the sand dunes east of Port Hedland.
89Currently, we do not model changes
90to the bathymetry or topography due to effects of the water flow.
91Therefore, we do not know whether these sand dunes would withstand the
92transmitted energy of the tsunami wave.
93The tsunami wave penetrates the river east of Port Hedland with a wave height
94over 2m at the mouth
[3373]95(Figure )
[3364]96and inundation
[3373]97exceeding 1m found at the Beadon Creek south of dock location (Figure
98).
[3364]99The wave penetrates the river east of Port Hedland with increasingly
100greater inundation between the -1.5m AHD and 1.5m AHD simulations.
101
102As expected, there is greater inundation at 1.5m AHD. The major road
103into Port Hedland, the ? Rd, remains free of inundation for
104all simulations with a small amount of inundation evident at HAT at
105the intersection with Beadon Creek Rd. Beadon Creek Rd services the wharf in the
106river which becomes increasingly inundated as the initial condition
[3373]107changes from 0m AHD to 3.9m AHD. Only the
[3364]108entry to the wharf on Beadon Creek Rd is sufficiently inundated to
[3373]109stop traffic at -3.6m AHD.
[3364]110At 1.5m AHD however, essentially the entire road would be impassable.
111
112There is significant inundation of at
[3373]113least 2m on the foreshore of Onslow for 0m AHD and 3.6m AHD.
[3364]114The inundation extent increases as the initial condition increases above 0m AHD,
115reaching the southern boundaries of
116the road infrastructure in the Port Hedland town centre.
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