Changeset 3404
- Timestamp:
- Jul 22, 2006, 3:14:04 PM (18 years ago)
- Location:
- production/onslow_2006/report
- Files:
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- 3 edited
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damage.tex (modified) (4 diffs)
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execsum.tex (modified) (1 diff)
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interpretation.tex (modified) (2 diffs)
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production/onslow_2006/report/damage.tex
r3402 r3404 56 56 ABS housing survey}. 57 57 The damage to the residential structures in the Onslow community 58 is summarised in Table \ref{table:damageoutput}. The percentage 58 is summarised in Table \ref{table:damageoutput}. As expected, the 59 greatest impact is found for the high tide scenario. The percentage 59 60 of repair cost to structural value shown is based on the total structural value 60 61 of \$71M. Likewise, the percentage of contents loss shown is … … 73 74 &Inundated & Collapsed & Repair Cost 74 75 & of Total Value & Losses & of Total Value \\ \hline 75 HAT & 100 &2&\$8M & 11\%&\$16M & \%16\\ \hline76 MSL & & 1 & \$ & \% & \$ & \%\\ \hline77 LAT & & & & && \\ \hline76 HAT & 100 &2&\$8M & 11\%&\$16M & 16 \% \\ \hline 77 MSL & 0 & 0 & \$0 & & \$0 & \\ \hline 78 LAT & 0 & 0 & \$0 & & \$0 & \\ \hline 78 79 \end{tabular} 79 80 \end{center} … … 87 88 &Minor & Moderate & Serious & Fatal \\ \hline 88 89 HAT & 10's & 10's & 10's & 10's \\ \hline 89 MSL & & & &\\ \hline90 LAT & & & &\\ \hline90 MSL & 0& 0 & 0 &0 \\ \hline 91 LAT & 0&0 & 0& 0\\ \hline 91 92 \end{tabular} 92 93 \end{center} … … 96 97 in the future as a number of communities exist in coastal regions of north west WA. 97 98 These communities are typically not included in national residential databases 98 and would be therefore overlooked in damage model estimates. 99 and would be therefore overlooked in damage model estimates 100 We can confirm that Bindi Bindi is not contained in the NBED. 99 101 There is one indigeneous community located in this study area as seen 100 in Figure 101 \ref{fig:points}.The population of the Bindibindi community is 140102 in Figure \ref{fig:points}. 103 The population of the Bindibindi community is 140 102 104 (18 \% of the Onslow population) 103 105 and is situated close to the coast as seen in Figure \ref{fig:points}. 104 During the HAT scenario, over 1m of water will inundate parts of the community (Figure 105 \ref{fig:gaugeBindiBindiCommunity}) causing significant impact. 106 During the HAT scenario, over 1 m of water will inundate parts of the community (Figure 107 \ref{fig:gaugeBindiBindiCommunity}) which would cause 108 significant impact. -
production/onslow_2006/report/execsum.tex
r3402 r3404 13 13 This report describes the modelling methodology and initial results 14 14 for a specific tsunami-genic event as it impacts the Onslow township 15 and its surrounds. Future studies 15 and its surrounds. In particular, maximum inundation maps are shown 16 and discussed 17 for the event occurring at mean sea level as well as 18 highest and lowest astronomical tide. The inundation results allow 19 estimation of the number of houses inundated and collapsed, as well as 20 the numbers of persons affected. The Onslow township has approximately 21 350 residential structures and a population of around 800. 22 For this specific event at high tide, approximately 23 100 houses are inundated with two of those collapsing. Approximately 24 15-20\% of the population will sustain injuries, including fatalities. 25 26 Future studies 16 27 will present a series of scenarios for a range of return periods to 17 assist FESA in developing appropriate plans for a range of event impacts. 28 assist FESA in developing appropriate plans for a range of event impacts. 29 This will also allow an assessment of the relative tsunami risk 30 to communities along the NW Shelf of WA. 18 31 This report and the decision support tool are the 19 June 2006 deliverables of the Collaborative Research Agreement 20 between FESA and GA, Tsunami Impact Modelling for WA.32 June 2006 deliverables of the Collaborative Research Agreement, 33 Tsunami Impact Modelling for WA, between FESA and GA. 21 34 -
production/onslow_2006/report/interpretation.tex
r3375 r3404 1 1 The main features of the 2 tsunami wave and resultant i mpactashore is described in this section.2 tsunami wave and resultant inundation ashore is described in this section. 3 3 We have 4 chosen a number of locations which we believe would be critical 5 in an emergency situation, such as the hospital and power station; or 6 effect recovery efforts, such as the airport and docks. These locations 4 chosen a number of locations to illustrate the features 5 of the tsunami as it approaches Onslow and runs ashore. 6 These locations have be chosen as we believe they would 7 either be critical 8 in an emergency situation, (e.g. the hospital and power station) or 9 effect recovery efforts, (e.g. the airport and docks). These locations 7 10 are described in Table \ref{table:locations} and shown in 8 Figure \ref{fig:points}. The water's stage and speed are shown 11 Figure \ref{fig:points}. The water's stage and speed 12 at each of these locations are shown 9 13 as a function of time in the series of graphs shown in 10 Appendix \ref{sec:timeseries}. Stage is defined as the absolute 11 water level relative to AHD. Both stage and speed are shown 14 Appendix \ref{sec:timeseries}. It is assumed that the earthquake is 15 generated at the beginning of the simulation, i.e. time = 0 minutes. 16 Stage is defined as the absolute 17 water level (in metres) relative to AHD 18 \footnote{For an offshore location such as Beadon Bay West, 19 the initial water level will be that of the tidal scenario. In the 20 case of MSL, this water level will be 0. As the tsunami wave moves 21 through this point, the water height may grow and thus the stage will represent the amplitude of the wave. For an onshore location such as the Light Tower, the actual water depth will be the difference between 22 the stage and the elevation at that point. Therefore, at the beginning 23 of the simulation, there will be no water onshore and therefore 24 the stage and the elevation will be identical.}. Both stage and speed 25 (in metres/second) for 26 each scenario (HAT, MSL and LAT) are shown 12 27 on consistent scales to allow comparison between point locations. 13 %The graphs show these time series for14 %the three cases; 1.5m AHD, 0m AHD and -1.5m AHD so that comparisons can15 %be made.16 28 As a useful benchmark, Table \ref{table:speedexamples} 17 describes typical examples for a range of velocities found in the29 describes typical examples for a range of speeds found in the 18 30 simulations. 19 31 20 \begin{table} 32 \begin{table}[h] 33 \label{table:speedexamples} 21 34 \begin{center} 22 35 \caption{Examples of a range of velocities.} … … 36 49 \end{table} 37 50 38 Examining the offshore locations shown in Appendix 39 \ref{sec:timeseries}, the drawdown prior to the tsunami wave 40 arriving at the shore can be seen to occur around 230 mins 41 (3.8 hours) after the tsunami is generated. 42 Prior to the drawdown, maximum amplitudes are approximately 50cm at 43 West of Groyne (Figure \ref{fig:gaugeWestofGroyne}) and 44 the mouth of Beadon Creek 45 (Figure \ref{fig:gaugeBeadonCreekmouth}), for example. 46 The first wave 47 after the drawdown ranges from approximately 2m in the 48 west of Beadon Bay (Figure \ref{fig:gaugeBeadonBaywest}) 49 to over 3m in the mouth of Beadon Creek 50 (Figure \ref{fig:gaugeBeadonCreekmouth}). 51 The speed 52 sharply increases at drawdown with further increases as the 53 wave grows in amplitude. 54 There is an increased amplitude of approximately 4m found in 55 east of Beadon Bay for the secondary wave, as opposed to the first wave. 56 This feature is also evident at the West of Groyne location but 57 with decreased amplitude. 58 This may be due to the geography of the bay, including the groyne west of 59 the creek mouth opening, the local bathymetry 60 and the direction of the tsunami wave. 51 A tsunami wave typically has a low amplitude and typically travels at 100's of kilometres per hour. The low amplitude complicates the ability to detect 52 the wave. As the water depth decreases, the speed of the wave 53 decreases and the amplitude grows. Another important feature of tsunamis 54 is drawdown. This means that the water is seen to retreat from the beaches 55 before a tsunami wave impacts that location. Other features 56 include reflections (where the wave is redirected due to the influence 57 of the coast) and shoaling (where the wave's amplitude increases ...). 61 58 62 The maximum speed found for the offshore locations occur at the West of 63 Groyne location (Figure \ref{fig:gaugeWestofGroyne}). 64 The speeds at west and east of Beadon Bay are quite similar 65 (Figure \ref{fig:gaugeBeadonBayeast} and Figure \ref{fig:gaugeBeadonBaywest}). 66 However, there are increased amplitudes (from drawdown to maximum 67 amplitude), in the eastern location which is in shallower water than the western 68 location. 69 Subsequent drawdowns are seen as the multitude of waves which make up the 70 event propagate towards the shore. 59 These features are seen in these scenarios, and are consistent 60 for HAT, MSL and LAT. There is a small wave, followed 61 by a large drawdown and then a large secondary wave. These 62 features are illustrated in Figure \ref{fig:gaugeBeadonBayeest} 63 where a small wave can be seen at around 200 mins. For the HAT 64 case (shown in blue), the amplitude 65 of the wave at this location is around 0.5 m\footnote{In this 66 scenario, the initial water level is 1.5 m, which means that 67 the actual amplitude is the difference between the stage value 68 and the initial water level; 2.? - 1.5). 69 The drawdown of around 4 m (i.e. 2.? - -2) then occurs at around 230 mins 70 (i.e. 3.8 hours after the event has been generated), before 71 the second wave arrives with an amplitude of over 3 m (i.e. 4.? - 72 -1.5). A further wave 73 is then evident a short time later (around 270 mins) 74 which further increases the amplitude to over 4.5 m (i.e. 6.? - -1.5). 75 These features are replicated at each of the offshore points (those 76 points with negative elevation as shown in Table \ref{table:locations}). 71 77 72 %At some gauge locations, these 73 %subsequent waves cause significantly increased inundation than that of 74 %the first wave. This is particularly seen at the Beadon Creek Docks, 75 %West of Groyne and Beadon Creek locations. 78 The wave amplitude is typically greater 79 for those locations which are in the shallowest water. For example, 80 the maximum wave amplitude at the Beadon Bay East location 81 (Figure \ref{fig:gaugeBeadonBayeast}) is over 82 4.5m where the water depth would normally be 3.56 m. In the 83 Beadon Bay West location (Figure \ref{fig:gaugeBeadonBaywest}) 84 where the water depth would normally be 4.62 m, 85 the maximum wave amplitude is much less (around 3 m). The wave amplitude 86 at the West of Groyne location (Figure \ref{fig:gaugeWestofGroyne}) 87 is not greater than that seen 88 at the Beadon Bay East location, even though the water depth is 89 much less, at 2.11m. This is probably due to its proximity 90 to the groyne\footnote{A groyne is a man made structure to combat 91 coastal erosion.} 92 which has impeded the tsunami wave to some degree. However, the 93 maximum speed found amongst the locations is at the West of Groyne 94 point which is in the shallowest water. 76 95 77 It is evident that the sand dunes west of 78 Onslow are very effective in halting the tsunami wave, 79 (see Figure \ref{fig:MSL_max_inundation}). 80 There is inundation between the western sand dunes at high 81 tide, Figure \ref{fig:HAT_max_inundation}, however, this water 82 penetrates from the north east (via 83 Onslow town centre) rather than seaward. (The DEM indicates that 84 this area is under 1.5m AHD which is automatically deemed to be inundated 85 at HAT.) 86 The same feature is evident for the sand dunes east of Onslow. 96 The speed of the tsunami sharply increases as it moves onshore. There 97 is minimal inundation found at the locations chosen, with the Bindi Bindi 98 community receiving the greatest inundation for all tidal scenarios. 99 At HAT, the community would receive over 1 m of inundation with 100 the water moving through the community at approximately 16 m/s. Referring 101 to Table \ref{table:speedexamples}, a person in this location could 102 not outrun this water movement. A small amount of water is found 103 at the hospital (? cm). Whilst this seems minimal, the water is moving 104 at around 6 m/s which could dislodge items such as trolleys and 105 wheelchairs if the water was able to enter the hospital. 106 107 The geography of the Onslow area has played a role in offering 108 some protection to the Onslow community. The tsunami wave is 109 travelling from the north west of the area. Most of 110 the inundation along the coast is that which is open to this 111 direction. 112 The sand dunes west of Onslow 113 appear to have halted this tsunami wave 114 (see Figure \ref{fig:MSL_max_inundation}) with limited 115 inundation found on the town's side of the dunes. 116 The inundation within the community has occurred due to the 117 wave reflecting from the beach area west of the creek and 118 returning towards the Onslow town itself. 119 There are also sand dunes east of the creek which have also 120 halted inundation beyond them. 87 121 Currently, we do not model changes 88 122 to the bathymetry or topography due to effects of the water flow. 89 123 Therefore, we do not know whether these sand dunes would withstand the 90 124 transmitted energy of the tsunami wave. 91 The tsunami wave penetrates the river east of Onslow with a wave height92 over 2m at the mouth93 (Figure \ref{fig:gaugeBeadonCreekmouth})94 and inundation95 exceeding 1m found at the Beadon Creek south of dock location (Figure96 \ref{fig:gaugeBeadonCreeksouthofdock}).97 The wave penetrates the river east of Onslow with increasingly98 greater inundation between the -1.5m AHD and 1.5m AHD simulations.99 125 100 As expected, there is greater inundation at 1.5m AHD. The major road 126 Water features such as rivers, creeks and estuaries also play a role 127 in the inundation extent. 128 The tsunami wave penetrates the creek east of Onslow with a wave height 129 over 2 m at the mouth 130 (Figure \ref{fig:gaugeBeadonCreekmouth}) for the HAT scenario. 131 Inundation exceeds 1 m at the Beadon Creek south of dock location (Figure 132 \ref{fig:gaugeBeadonCreeksouthofdock}) suggesting that the wave's 133 energy dissipates as inundation overflows from the creek. A large 134 tidal flat region surrounds the southern parts of the creek and 135 it is evident that the inundation is essentially caught in this 136 area. 137 138 As expected, there is greater inundation at HAT with increased 139 extent. The major road 101 140 into Onslow, the Onslow Mount Stuart Rd, remains free of inundation for 102 all simulations with a small amount of inundation evident at HAT at141 all tidal scenarios with a small amount of inundation evident at HAT at 103 142 the intersection with Beadon Creek Rd. Beadon Creek Rd services the wharf in the 104 river which 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 to 107 stop traffic at -1.5m AHD. 108 At 1.5m AHD however, essentially the entire road would be impassable. 143 creek which becomes increasingly inundated as the tide height 144 increases. The only road sufficiently inundated at LAT is Beadon 145 Creek Rd near the entry to the wharf. This road during the HAT 146 scenario would be impassable as the water depths are consistently 147 over 1 m with a maximum water depth of around 2 m found close to 148 the wharf. 109 149 110 150 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 as the initial condition increases above 0m AHD, 113 reaching the southern boundaries of 114 the road infrastructure in the Onslow town centre. 151 least 2 m on the foreshore of Onslow for MSL and HAT. 152 The inundation extends further as the tidal heights increase. 153 At HAT, the inundation reaches the southern boundaries of 154 the road infrastructure in the Onslow town centre. 155 The airport remains 156 free of inundation for each tidal scenario. Section \ref{sec:damage} 157 details the impact estimates to the residential infrastructure.
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