Changeset 3976

Nov 14, 2006, 9:45:27 AM (17 years ago)

hobart report updates

3 added
4 edited


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

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    37   %\centerline{ \includegraphics[scale=0.15]{../report_figures/hobart_resolution_zones.jpg}}
     37  \centerline{ \includegraphics[scale=0.15]{../report_figures/refined_model.jpg}}
    3939  \caption{Study area for the Hobart scenario highlighting four regions of increased refinement.
    40 Region 1: Surrounds the coastal region with a cell area of 2500 m$^2$ (lateral accuracy 70 m).
     40  The Bruny, Site 13 and Kingston regions surrounds a paleo site identified in Chris Sharples report.
     41  The cell area in these regions are 500 m$^2$ (lateral accuracy 70 m).
     42Region 4: Surrounds the coastal region with a cell area of 2500 m$^2$ (lateral accuracy 70 m).
     43The remaining parts of the model have a resolution of m$^2$ (lateral accuracy  m).
    4245  \label{fig:hobart_area}
  • anuga_work/production/hobart_2006/report/interpretation.tex

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    33We have
    44chosen a number of locations to illustrate the features
    5 of the tsunami as it approaches and impact South East Tasmania.
     5of the tsunami as it approaches and impacts South East Tasmania.
    66These locations align with those in the paleotsunami report.
    77These locations
    1313generated at the beginning of the simulation, i.e. time = 0 minutes.
    1414Stage is defined as the absolute
    15 water level (in metres) relative to AHD
    16 \footnote{For an offshore location such as Beadon Bay West,
    17 the initial water level will be that of the tidal scenario. In the
    18 case of MSL, this water level will be 0. As the tsunami wave moves
    19 through this point, the water height may grow and thus the stage will
    20 represent the amplitude of the wave. For an onshore location such as the
    21 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
     15water level (in metres) relative to AHD. Both stage and speed
    2516(in metres/second) for
    2617each scenario (Mw 8.7 and Mw 8.5) are shown
    6354by a large drawdown and then a large secondary wave.
    65 These
    66 features are illustrated in Figure \ref{fig:gaugeBeadonBayeast}
    67 where a small wave can be seen at around 200 mins. For the HAT
    68 case (shown in blue), the amplitude
    69 of the wave at this location is around 0.8 m\footnote{In this
    70 scenario, the initial water level is 1.5 m, which means that
    71 the actual amplitude is the difference between the stage value
    72 and the initial water level; 2.3 - 1.5}.
    73 The drawdown of around 4.3 m (i.e. 2.3 - -2) then occurs at around 230 mins
    74 (i.e. 3.8 hours after the event has been generated), before
    75 the second wave arrives
    76 with an amplitude of around 3.6 m (i.e. 4.1 - 1.5). A further wave
    77 is then evident a short time later (around 255 mins)
    78 which further increases the amplitude to around 5 m (i.e. 6.6 - 1.5).
    79 These features are replicated at each of the offshore points (those
    80 points with negative elevation as shown in Table \ref{table:locations}).
     56The bathymetry and geography of the region has played a role in
     57directing or attentuating the tsunami wave. The tsunami wave is
     58travelling from the south west of the area. The wave is seen to attentuate as it
     59travels towards the Derwent River.
    82 The wave amplitude is typically greater
    83 for those locations which are in the shallowest water. For example,
    84 the maximum wave amplitude at the Beadon Bay East location
    85 (Figure \ref{fig:gaugeBeadonBayeast}) is over
    86 4.5m where the water depth would normally be 3.56 m. In the
    87 Beadon Bay West location (Figure \ref{fig:gaugeBeadonBaywest})
    88 where the water depth would normally be 4.62 m,
    89 the maximum wave amplitude is much less (around 3 m). The wave amplitude
    90 at the West of Groyne location (Figure \ref{fig:gaugeWestofGroyne})
    91 is not greater than that seen
    92 at the Beadon Bay East location, even though the water depth is
    93 much less, at 2.11m. This is probably due to its proximity
    94 to the groyne\footnote{A groyne is a man made structure to combat
    95 coastal erosion.}
    96 which has impeded the tsunami wave to some degree. However, the
    97 maximum speed found amongst the locations is at the West of Groyne
    98 point which is in the shallowest water.
    100 The speed of the tsunami sharply increases as it moves onshore. There
    101 is minimal inundation found at the locations chosen, with the Bindi Bindi
    102 community receiving the greatest inundation for all tidal scenarios.
    103 At HAT, the community would receive over 1 m of inundation with
    104 the water moving through the community at approximately 16 m/s. Referring
    105 to Table \ref{table:speedexamples}, a person in this location could
    106 not outrun this water movement. A small amount of water is found
    107 at the hospital (10 cm). Whilst this seems minimal, the water is moving
    108 at around 6 m/s which could dislodge some items if the water was able to enter the hospital.
    110 The geography of the Onslow area has played a role in offering
    111 some protection to the Onslow community. The tsunami wave is
    112 travelling from the north west of the area. Most of
    113 the inundation along the coast is that which is open to this
    114 direction. 
    115 The sand dunes west of Onslow
    116 appear to have halted this tsunami wave
    117 (see Figure \ref{fig:MSL_max_inundation}) with limited
    118 inundation found on the town's side of the dunes.
    119 The inundation within the community has occurred due to the
    120 wave reflecting from the beach area west of the creek and
    121 returning towards the Onslow town itself. 
    122 There are also sand dunes east of the creek which have also
    123 halted inundation beyond them.
    124 Currently, we do not model changes
    125 to the bathymetry or topography due to effects of the water flow.
    126 Therefore, we do not know whether these sand dunes would withstand the
    127 transmitted energy of the tsunami wave.
  • anuga_work/production/hobart_2006/report/mw87_map.tex

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    2 %\centerline{ \includegraphics[width=\paperwidth]{../report_figures/mw87.jpg}}
    3 \caption{Maximum inundation map for the Mw 8.7 scenario for South East Tasmania.
     2\centerline{ \includegraphics[width=\paperwidth]{../report_figures/site13refined.jpg}}
     3\caption{Maximum inundation map for the Mw 8.7 scenario for Site 13.
    44Data: TAS DPIW, UTAS and Hobart Port Authority and AHO.} 
    5 \label{fig:mw87_max_inundation}
     9\centerline{ \includegraphics[width=\paperwidth]{../report_figures/kingston.jpg}}
     10\caption{Maximum inundation map for the Mw 8.7 scenario for Kingston.
     11Data: TAS DPIW, UTAS and Hobart Port Authority and AHO.} 
  • anuga_work/production/hobart_2006/report/summary.tex

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    1 This report has described the impact on Onslow from a tsunami
    2 generated by a Mw 9 earthquake on the Sunda Arc subduction zone
    3 occurring at Highest Astronomical Tide, Lowest Astronomical Tide
    4 and Mean Sea Level.
     1This report has described the tsunami inundation to selected
     2sites in South East Tasmania which have been
     3generated by a Mw 8.7 earthquake on the Puysegur Trecnh
     4occurring at Mean Sea Level.
    55As yet, there is no knowledge of the return period for this event. The
    6 modelling methodology, assumptions and data sources for the Onslow
     6modelling methodology, assumptions and data sources for the South East Tasmania
    77scenario have also been described.
    9 As shown in Section \ref{sec:data}, it is imperative
    10 that the best available data is used to increase confidence
    11 in the inundation maps.
    12 Given that the Highest Astronomical Tide contour
    13 line is further from the coast for the DTED data than the DLI data, we
    14 expect the inundation to extend further and thus be greater than
    15 that seen in Figure \ref{fig:MSL_max_inundation}.
    16 The impact modelling
    17 will result in significantly inflated structural and contents loss figures as well as
    18 numbers of people affected.
    19 These results strongly point to the need for the best
    20 available data so that more accurate predictions regarding the
    21 inundation can be made.
    22 An onshore grid resolution of the order
    23 of tens of metres is required, however, it is more important that the data
    24 are accurate (or at least well known).
    26 These scenarios will be revisited once the probabilistic models
    27 are complete so that a suite of tsunami impact assessments can be made.
    28 Future activities to support the impact studies on the North West Shelf
    29 include:
    31 \begin{itemize}
    32 \item Sourcing of data sets,
    33 \item Investigation of solution sensitivity to cell resolution,
    34 bathymetry and tsunami source uncertainties,
    35 \item Location of boundary for simulation study area, and
    36 \item Investigation of friction coefficients.
    37 \end{itemize}
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