# Changeset 3976

Ignore:
Timestamp:
Nov 14, 2006, 9:45:27 AM (16 years ago)
Message:

Location:
anuga_work/production/hobart_2006
Files:
4 edited

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• ## anuga_work/production/hobart_2006/report/computational_setup.tex

 r3729 \begin{figure}[hbt] %\centerline{ \includegraphics[scale=0.15]{../report_figures/hobart_resolution_zones.jpg}} \centerline{ \includegraphics[scale=0.15]{../report_figures/refined_model.jpg}} \caption{Study area for the Hobart scenario highlighting four regions of increased refinement. Region 1: Surrounds the coastal region with a cell area of 2500 m$^2$ (lateral accuracy 70 m). The Bruny, Site 13 and Kingston regions surrounds a paleo site identified in Chris Sharples report. The cell area in these regions are 500 m$^2$ (lateral accuracy 70 m). Region 4: Surrounds the coastal region with a cell area of 2500 m$^2$ (lateral accuracy 70 m). The remaining parts of the model have a resolution of m$^2$ (lateral accuracy  m). } \label{fig:hobart_area}
• ## anuga_work/production/hobart_2006/report/interpretation.tex

 r3721 We have chosen a number of locations to illustrate the features of the tsunami as it approaches and impact South East Tasmania. of the tsunami as it approaches and impacts South East Tasmania. These locations align with those in the paleotsunami report. These locations generated at the beginning of the simulation, i.e. time = 0 minutes. Stage is defined as the absolute water level (in metres) relative to AHD \footnote{For an offshore location such as Beadon Bay West, the initial water level will be that of the tidal scenario. In the case of MSL, this water level will be 0. As the tsunami wave moves 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 the stage and the elevation at that point. Therefore, at the beginning of the simulation, there will be no water onshore and therefore the stage and the elevation will be identical.}. Both stage and speed water level (in metres) relative to AHD. Both stage and speed (in metres/second) for each scenario (Mw 8.7 and Mw 8.5) are shown by a large drawdown and then a large secondary wave. These features are illustrated in Figure \ref{fig:gaugeBeadonBayeast} where a small wave can be seen at around 200 mins. For the HAT case (shown in blue), the amplitude of the wave at this location is around 0.8 m\footnote{In this scenario, the initial water level is 1.5 m, which means that the actual amplitude is the difference between the stage value and the initial water level; 2.3 - 1.5}. The drawdown of around 4.3 m (i.e. 2.3 - -2) then occurs at around 230 mins (i.e. 3.8 hours after the event has been generated), before the second wave arrives with an amplitude of around 3.6 m (i.e. 4.1 - 1.5). A further wave is then evident a short time later (around 255 mins) which further increases the amplitude to around 5 m (i.e. 6.6 - 1.5). These features are replicated at each of the offshore points (those points with negative elevation as shown in Table \ref{table:locations}). The bathymetry and geography of the region has played a role in directing or attentuating the tsunami wave. The tsunami wave is travelling from the south west of the area. The wave is seen to attentuate as it travels towards the Derwent River. The wave amplitude is typically greater for those locations which are in the shallowest water. For example, the maximum wave amplitude at the Beadon Bay East location (Figure \ref{fig:gaugeBeadonBayeast}) is over 4.5m where the water depth would normally be 3.56 m. In the Beadon Bay West location (Figure \ref{fig:gaugeBeadonBaywest}) where the water depth would normally be 4.62 m, the maximum wave amplitude is much less (around 3 m). The wave amplitude at the West of Groyne location (Figure \ref{fig:gaugeWestofGroyne}) is not greater than that seen at the Beadon Bay East location, even though the water depth is much less, at 2.11m. This is probably due to its proximity to the groyne\footnote{A groyne is a man made structure to combat coastal erosion.} which has impeded the tsunami wave to some degree. However, the maximum speed found amongst the locations is at the West of Groyne point which is in the shallowest water. The speed of the tsunami sharply increases as it moves onshore. There is minimal inundation found at the locations chosen, with the Bindi Bindi community receiving the greatest inundation for all tidal scenarios. At HAT, the community would receive over 1 m of inundation with the water moving through the community at approximately 16 m/s. Referring to Table \ref{table:speedexamples}, a person in this location could not outrun this water movement. A small amount of water is found at the hospital (10 cm). Whilst this seems minimal, the water is moving at around 6 m/s which could dislodge some items if the water was able to enter the hospital. The geography of the Onslow area has played a role in offering some protection to the Onslow community. The tsunami wave is travelling from the north west of the area. Most of the inundation along the coast is that which is open to this direction. The sand dunes west of Onslow appear to have halted this tsunami wave (see Figure \ref{fig:MSL_max_inundation}) with limited inundation found on the town's side of the dunes. The inundation within the community has occurred due to the wave reflecting from the beach area west of the creek and returning towards the Onslow town itself. There are also sand dunes east of the creek which have also halted inundation beyond them. Currently, we do not model changes to the bathymetry or topography due to effects of the water flow. Therefore, we do not know whether these sand dunes would withstand the transmitted energy of the tsunami wave.
• ## anuga_work/production/hobart_2006/report/mw87_map.tex

 r3729 \begin{sidewaysfigure} %\centerline{ \includegraphics[width=\paperwidth]{../report_figures/mw87.jpg}} \caption{Maximum inundation map for the Mw 8.7 scenario for South East Tasmania. \centerline{ \includegraphics[width=\paperwidth]{../report_figures/site13refined.jpg}} \caption{Maximum inundation map for the Mw 8.7 scenario for Site 13. Data: TAS DPIW, UTAS and Hobart Port Authority and AHO.} \label{fig:mw87_max_inundation} \label{fig:site13maxinundation} \end{sidewaysfigure} \begin{sidewaysfigure} \centerline{ \includegraphics[width=\paperwidth]{../report_figures/kingston.jpg}} \caption{Maximum inundation map for the Mw 8.7 scenario for Kingston. Data: TAS DPIW, UTAS and Hobart Port Authority and AHO.} \label{fig:kingstonmaxinundation} \end{sidewaysfigure}
• ## anuga_work/production/hobart_2006/report/summary.tex

 r3721 This report has described the impact on Onslow from a tsunami generated by a Mw 9 earthquake on the Sunda Arc subduction zone occurring at Highest Astronomical Tide, Lowest Astronomical Tide and Mean Sea Level. This report has described the tsunami inundation to selected sites in South East Tasmania which have been generated by a Mw 8.7 earthquake on the Puysegur Trecnh occurring at Mean Sea Level. As yet, there is no knowledge of the return period for this event. The modelling methodology, assumptions and data sources for the Onslow modelling methodology, assumptions and data sources for the South East Tasmania scenario have also been described. As shown in Section \ref{sec:data}, it is imperative that the best available data is used to increase confidence in the inundation maps. Given that the Highest Astronomical Tide contour line is further from the coast for the DTED data than the DLI data, we expect the inundation to extend further and thus be greater than that seen in Figure \ref{fig:MSL_max_inundation}. The impact modelling will result in significantly inflated structural and contents loss figures as well as numbers of people affected. These results strongly point to the need for the best available data so that more accurate predictions regarding the inundation can be made. An onshore grid resolution of the order of tens of metres is required, however, it is more important that the data are accurate (or at least well known). These scenarios will be revisited once the probabilistic models are complete so that a suite of tsunami impact assessments can be made. Future activities to support the impact studies on the North West Shelf include: \begin{itemize} \item Sourcing of data sets, \item Investigation of solution sensitivity to cell resolution, bathymetry and tsunami source uncertainties, \item Location of boundary for simulation study area, and \item Investigation of friction coefficients. \end{itemize}
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