source: production/onslow_2006/report/interpretation.tex @ 3237

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1
2The main features of the
3tsunami wave and resultant impact ashore is described in this section.
4To assist this description, we have
5chosen a number of locations which we believe would be important
6in an emergency situation, such as the hospital and power station, or
7effect recovery efforts, such as the airport and docks. These locations
8are described in table \ref{table:locations} and shown in
9Figure \ref{fig:points}. The water's stage and speed are shown
10as a function of time in the series of graphs shown in
11Section \ref{sec:timeseries}. Stage is defined as the absolute
12water level relative to AHD. Both stage and spped are shown
13on consistent scales to compare between point locations.
14%The graphs show these time series for
15%the three cases; 1.5m AHD, 0m AHD and -1.5m AHD so that comparisons can
16%be made.
17As a useful benchmark, Table \ref{table:speedexamples}
18describes typical examples for a range of velocities found in the
19simulations.
20
21\begin{table}
22\label{table:speedexamples}
23\caption{Examples of a range of velocities.}
24\begin{center}
25\begin{tabular}{|l|l|}\hline
26Velocity (m/s) & Example \\ \hline
271 & leisurely stroll pace\\ \hline
281.5 & average walking pace \\ \hline
292 & 100m Olympic male freestyle \\ \hline
303 & mackeral \\ \hline
314 & average person maintain for 1000m \\ \hline
325 & blue whale \\ \hline
3310 & 100m Olympic male sprinter \\ \hline
3416 & car travelling in urban zones (60 km/hr) \\ \hline
35\end{tabular}
36\end{center}
37\end{table}
38
39
40Examining the offshore locations shown in Section \ref{sec:timeseries},
41the drawdown prior to the tsunami wave
42arriving at the shore can be seen to occur around 230 mins 
43(3.8 hours) after the tsunami is generated.
44Prior to the drawdown, maximum amplitudes are approximately 50cm at
45West of Groyne (Figure \ref{fig:20060515001733gaugeWestofGroyne}) and
46the mouth of Beadon Creek
47(Figure \ref{fig:20060515001733gaugeBeadonCreekmouth}), for example.
48The first wave
49after the drawdown ranges from approximately 2m in the
50west of Beadon Bay (Figure \ref{fig:20060515001733gaugeBeadonBaywest})
51to 1.5m in the east of Beadon Bay
52(Figure \ref{fig:20060515001733gaugeBeadonBayeast}).
53The speed
54sharply increases at drawdown with further increases as the
55wave grows in amplitude.
56There is an increased amplitude of approximately 3m found in
57east of Beadon Bay for the secondary wave, as opposed to the first wave.
58This feature is also evident at the West of Groyne location.
59This may be due to the geography of the bay, including the groyne west of
60the creek mouth opening, the local bathymetry
61and the direction of the tsunami wave.
62
63The maximum speed found for the offshore locations occur at the West of
64Groyne location (Figure \ref{fig:20060515001733gaugeWestofGroyne})
65with speeds halved at the Beadon Bay west location.
66The Beadon Bay west speed is greater than the east of Beadon
67Bay location (Figure \ref{fig:20060515001733gaugeBeadonBayeast}).
68There is similar differences in amplitude (from drawdown to maximum
69amplitude), however, the western location is in deeper water than the eastern
70location which may indicate the increased speed found in the east of the
71bay.  Subsequent drawdowns are seen as the multitude of waves which make up the
72event (see Figure \ref{fig:MOSTsolution}) 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
79It is evident that the sand dunes west of
80Onslow are very effective in halting the tsunami wave which rise to approximately
8110m in height,
82see Figure \ref{fig:MSL_max_inundation}.
83%There is inundation between the sand dunes at high
84%tide, Figure \ref{fig:HAT_max_inundation}, however, this water
85%penetrated from the north east (via
86%Onslow town centre) rather than seaward.
87The same feature is evident for the sand dunes east of Onslow which
88rise to 15m in height. Currently, we do not model changes
89to the bathymetry or topography due to effects of the water flow.
90Therefore, we do not know whether these sand dunes would withstand the
91transmitted energy of the tsunami wave.
92The tsunami wave penetrates the river east of Onslow with wave height
93approximately 2m at the mouth
94(Figure \ref{fig:20060515001733gaugeBeadonCreekmouth})
95and inundation
96exceeding 1m found at the Beadon Creek south of dock location (Figure
97\ref{fig:20060515001733gaugeBeadonCreeksouthofdock}).
98%The wave penetrates the river east of Onslow with increasingly
99%greater inundation between the -1.5m AHD and 1.5m AHD simulations.
100
101%As expected, there is greater inundation at 1.5m AHD. The major road
102%into Onslow, the Onslow Mount Stuart Rd, remains free of inundation for
103%all simulations. Beadon Creek Rd which services the wharf in the
104%river becomes increasingly inundated as the initial condition
105%changes from 0m AHD to 1.5m AHD. Only the
106%entry to the wharf on Beadon Creek Rd is sufficiently inundated at -1.5m AHD
107%to stop traffic. At 1.5m AHD however, essentially the entire road
108%would be impassable.
109
110%There is significant inundation of at
111%least 2m on the foreshore of Onslow for 0m AHD and 1.5m AHD.
112%The inundation extent increases the initial condition increases above 0m AHD,
113%pushing the edges
114%of the majority of the road infrastructure in the Onslow town centre.
115There is significant inundation of at least 2m on the foreshore of Onslow.
116The major road into Onslow, the Onslow Mount Stuart Rd, remains free
117of inundation, however there is some inundation on Beadon Creek Rd
118which services the wharf in the river.
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