[3240] | 1 | The main features of the |
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| 2 | tsunami wave and resultant impact ashore is described in this section. |
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| 3 | To assist this description, we have |
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| 4 | chosen a number of locations which we believe would be important |
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| 5 | in an emergency situation, such as the hospital and power station, or |
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| 6 | effect recovery efforts, such as the airport and docks. These locations |
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| 7 | are described in Table \ref{table:locations} and shown in |
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| 8 | Figure \ref{fig:points}. The water's stage and speed are shown |
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| 9 | as a function of time in the series of graphs shown in |
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| 10 | Section \ref{sec:timeseries}. Stage is defined as the absolute |
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| 11 | water level relative to AHD. Both stage and spped are shown |
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| 12 | on consistent scales to allow comparison between point locations. |
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| 13 | %The graphs show these time series for |
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| 14 | %the three cases; 1.5m AHD, 0m AHD and -1.5m AHD so that comparisons can |
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| 15 | %be made. |
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| 16 | As a useful benchmark, Table \ref{table:speedexamples} |
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| 17 | describes typical examples for a range of velocities found in the |
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| 18 | simulations. |
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| 19 | |
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| 20 | \begin{table} |
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| 21 | \label{table:speedexamples} |
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| 22 | \caption{Examples of a range of velocities.} |
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| 23 | \begin{center} |
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| 24 | \begin{tabular}{|l|l|}\hline |
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| 25 | {\bf Velocity (m/s)} & {\bf Example} \\ \hline |
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| 26 | 1 & leisurely stroll pace\\ \hline |
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| 27 | 1.5 & average walking pace \\ \hline |
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| 28 | 2 & 100m Olympic male freestyle \\ \hline |
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| 29 | 3 & mackeral \\ \hline |
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| 30 | 4 & average person maintain for 1000m \\ \hline |
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| 31 | 5 & blue whale \\ \hline |
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| 32 | 10 & 100m Olympic male sprinter \\ \hline |
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| 33 | 16 & car travelling in urban zones (60 km/hr) \\ \hline |
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| 34 | \end{tabular} |
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| 35 | \end{center} |
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| 36 | \end{table} |
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| 37 | |
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| 38 | Examining the offshore locations shown in Section \ref{sec:timeseries}, |
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| 39 | the drawdown prior to the tsunami wave |
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| 40 | arriving at the shore can be seen to occur around 230 mins |
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| 41 | (3.8 hours) after the tsunami is generated. |
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| 42 | Prior to the drawdown, maximum amplitudes are approximately 50cm at |
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| 43 | West of Groyne (Figure \ref{fig:20060515001733gaugeWestofGroyne}) and |
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| 44 | the mouth of Beadon Creek |
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| 45 | (Figure \ref{fig:20060515001733gaugeBeadonCreekmouth}), for example. |
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| 46 | The first wave |
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| 47 | after the drawdown ranges from approximately 2m in the |
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| 48 | west of Beadon Bay (Figure \ref{fig:20060515001733gaugeBeadonBaywest}) |
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| 49 | to 1.5m in the east of Beadon Bay |
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| 50 | (Figure \ref{fig:20060515001733gaugeBeadonBayeast}). |
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| 51 | The speed |
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| 52 | sharply increases at drawdown with further increases as the |
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| 53 | wave grows in amplitude. |
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| 54 | There is an increased amplitude of approximately 3m found in |
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| 55 | east of Beadon Bay for the secondary wave, as opposed to the first wave. |
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| 56 | This feature is also evident at the West of Groyne location. |
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| 57 | This may be due to the geography of the bay, including the groyne west of |
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| 58 | the creek mouth opening, the local bathymetry |
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| 59 | and the direction of the tsunami wave. |
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| 60 | |
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| 61 | The maximum speed found for the offshore locations occur at the West of |
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| 62 | Groyne location (Figure \ref{fig:20060515001733gaugeWestofGroyne}) |
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| 63 | with speeds halved at the Beadon Bay west location. |
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| 64 | The speed at west of Beadon Bay is greater than the east of Beadon |
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| 65 | Bay location (Figure \ref{fig:20060515001733gaugeBeadonBayeast}). |
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| 66 | There is similar differences in amplitude (from drawdown to maximum |
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| 67 | amplitude), however, the western location is in deeper water than the eastern |
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| 68 | location which may indicate the increased speed found in the east of the |
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| 69 | bay. Subsequent drawdowns are seen as the multitude of waves which make up the |
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| 70 | event (see Figure \ref{fig:MOSTsolution}) propagate towards the shore. |
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| 71 | |
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| 72 | %At some gauge locations, these |
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| 73 | %subsequent waves cause significantly increased inundation than that of |
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| 74 | %the first wave. This is particularly seen at the Beadon Creek Docks, |
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| 75 | %West of Groyne and Beadon Creek locations. |
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| 76 | |
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| 77 | It is evident that the sand dunes west of |
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| 78 | Onslow are very effective in halting the tsunami wave which rise to approximately |
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| 79 | 10m in height, |
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| 80 | see Figure \ref{fig:MSL_max_inundation}. |
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| 81 | %There is inundation between the sand dunes at high |
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| 82 | %tide, Figure \ref{fig:HAT_max_inundation}, however, this water |
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| 83 | %penetrated from the north east (via |
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| 84 | %Onslow town centre) rather than seaward. |
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| 85 | The same feature is evident for the sand dunes east of Onslow which |
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| 86 | rise to 15m in height. Currently, we do not model changes |
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| 87 | to the bathymetry or topography due to effects of the water flow. |
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| 88 | Therefore, we do not know whether these sand dunes would withstand the |
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| 89 | transmitted energy of the tsunami wave. |
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| 90 | The tsunami wave penetrates the river east of Onslow with wave height |
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| 91 | approximately 2m at the mouth |
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| 92 | (Figure \ref{fig:20060515001733gaugeBeadonCreekmouth}) |
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| 93 | and inundation |
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| 94 | exceeding 1m found at the Beadon Creek south of dock location (Figure |
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| 95 | \ref{fig:20060515001733gaugeBeadonCreeksouthofdock}). |
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| 96 | %The wave penetrates the river east of Onslow with increasingly |
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| 97 | %greater inundation between the -1.5m AHD and 1.5m AHD simulations. |
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| 98 | |
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| 99 | %As expected, there is greater inundation at 1.5m AHD. The major road |
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| 100 | %into Onslow, the Onslow Mount Stuart Rd, remains free of inundation for |
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| 101 | %all simulations. Beadon Creek Rd which services the wharf in the |
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| 102 | %river becomes increasingly inundated as the initial condition |
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| 103 | %changes from 0m AHD to 1.5m AHD. Only the |
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| 104 | %entry to the wharf on Beadon Creek Rd is sufficiently inundated at -1.5m AHD |
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| 105 | %to stop traffic. At 1.5m AHD however, essentially the entire road |
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| 106 | %would be impassable. |
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| 107 | |
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| 108 | %There is significant inundation of at |
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| 109 | %least 2m on the foreshore of Onslow for 0m AHD and 1.5m AHD. |
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| 110 | %The inundation extent increases the initial condition increases above 0m AHD, |
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| 111 | %pushing the edges |
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| 112 | %of the majority of the road infrastructure in the Onslow town centre. |
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| 113 | There is significant inundation of at least 2m on the foreshore of Onslow. |
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| 114 | The major road into Onslow, the Onslow Mount Stuart Rd, remains free |
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| 115 | of inundation, however there is some inundation on Beadon Creek Rd |
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| 116 | which services the wharf in the river. |
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