Changeset 3402


Ignore:
Timestamp:
Jul 21, 2006, 5:28:16 PM (18 years ago)
Author:
sexton
Message:

incorporating Trevor Dhu's comments

Location:
production/onslow_2006/report
Files:
9 edited

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  • production/onslow_2006/report/anuga.tex

    r3390 r3402  
    1414according to areas of interest and that wetting and drying
    1515is treated robustly as part of the numerical scheme.}.
    16 ANUGA is continually being developed and validated to ensure
     16ANUGA is continually being refined and validated to ensure
    1717the modelling approximations are as accurate as possible.
    1818However, model sensitivity to errors in bathymetric data,
     
    4343thus it has not been incorporated
    4444in the scenario. The
    45 results are therefore likely to be over estimations.
     45results are therefore likely to be over estimates.
    4646
  • production/onslow_2006/report/computational_setup.tex

    r3393 r3402  
    11To set up a model for the tsunami scenario, a study area is first
    2 determined. Preliminary investigations have indicated the point
    3 at which the output from MOST is the input to ANUGA is
    4 sufficient at the 100m bathymetric contour line\footnote{
     2determined. Preliminary investigations have indicated that the
     3output from MOST should be input to ANUGA
     4at the 100m water depth\footnote{
    55Preliminary investigations indicate that MOST and ANUGA compare
    6 well at the 100m contour line. In addition, the resolution for
    7 the MOST modelling indicate that it can theoretically model
    8 tsunamis with a wavelength of 20-30km, and the wavelength of
    9 the tsunami wave at the boundary is approximately 20km. A much
     6well at a water depth of 100 m. In addition, the resolution for
     7the MOST modelling indicate that it can theoretically model a
     8tsunami wave with a wavelength of 20-30 km. The wavelength of
     9the tsunami wave at the boundary in this scenario is approximately 20 km. A much
    1010higher model resolution will be used in developing the probabilistic
    11 models for further studies.}. Historical run-up heights are
    12 of the order of 10m and we would expect that a tsunami wave
    13 would penetrate no higher for this scenario.
     11models for further studies so that tsunami waves with shorter wavelengths
     12can be captured.}. Historical run-up heights are
     13of the order of 10 m and we would expect that a tsunami wave
     14would penetrate no higher for this scenario, hence we have
     15bounded our study region at 10m elevation.
    1416Current computation requirements define a coastline
    15 extent of around 100km. Therefore, the study area of around 6300 km$^2$
    16 covers approximately 100km of
     17extent of around 100 km. Therefore, the study area of around 6300 km$^2$
     18covers approximately 100 km of
    1719coastline and extends offshore to the 100m contour line and inshore to
    1820approximately 10m elevation.
    1921
    20 The finite volume technique relies on the construction of a triangular mesh which covers the study region. This mesh can be altered to suit the needs of the scenario in question. The mesh can be refined in areas of interest, particularly in the coastal region where complex behaviour is likely to occur. In setting up the model, the user defines the area of the triangular cells in each region of interest\footnote{Note that the cell
     22The finite volume technique relies on the construction of a triangular mesh which covers the study region.
     23This mesh can be altered to suit the needs of the scenario in question. The mesh can be refined in areas of
     24interest, particularly in the coastal region where complex behaviour is likely to occur.
     25In setting up the model, the user defines the area of the triangular cells in each region of interest\footnote{Note that the cell
    2126area will be the maximum cell area within the defined region and that each
    2227cell in the region does not necessarily have the same area.}.
    23 The area should not be too small as to exceed realistic computational time, and not too great as to inadequately capture important behaviour. There are no gains in choosing the area to be less than the supporting data.
    24 Figure \ref{fig:onslow_area} shows the study area and where further mesh refinement has been made. For each region, a maximum triangular cell area is defined and its associated lateral accuracy.
    25 With these cell areas, the study area consists of 401939 triangles
    26 in which water levels and momentums are tracked through time. The lateral accuracy refers to the distance at which we are confident in stating a region is inundated. Therefore we can only be confident in the calculated inundation extent in the Onslow town centre to within 30m.
     28The cell areas should not be too small as this will cause unrealisticly long computational time,
     29and not too great as this may inadequately capture important behaviour.
     30%There are no gains in choosing the area to be less than the supporting data.
     31Figure \ref{fig:onslow_area} shows the study area with regions of difference cell areas. The total number
     32of cells is 401939.
     33Lateral accuracy refers to the distance at which we are confident in stating a region is inundated.
     34Figure \ref{fig:onslow_area} shows the maximum triangular cell area and lateral accuracy for each region.
     35Therefore we can only be confident in the calculated inundation extent in the Onslow town centre to within 30 m.
     36
    2737
    2838\begin{figure}[hbt]
    2939
    30   \centerline{ \includegraphics[scale=0.15]
    31              {../report_figures/onslow_resolution_zones.jpg}}
     40  \centerline{ \includegraphics[scale=0.15]{../report_figures/onslow_resolution_zones.jpg}}
    3241
    3342  \caption{Study area for Onslow scenario highlighting four regions of increased refinement.
    34 Region 1: Surrounds Onslow town centre with a cell area of 500 m$^2$ (lateral accuracy 30m).
    35 Region 2: Surrounds the coastal region with a cell area of 2500 m$^2$ (lateral accuracy 70m).
    36 Region 3: Water depths to the 50m contour line (approximately) with a cell area of 20000 m$^2$ (lateral accuracy 200m).
    37 Region 4: Water depths to the boundary (approximately 100m contour line) with a cell area of 100000 m$^2$ (lateral accuracy 445m).
     43Region 1: Surrounds Onslow town centre with a cell area of 500 m$^2$ (lateral accuracy 30 m).
     44Region 2: Surrounds the coastal region with a cell area of 2500 m$^2$ (lateral accuracy 70 m).
     45Region 3: Water depths to the 50m contour line (approximately) with a cell area of 20000 m$^2$ (lateral accuracy 200 m).
     46Region 4: Water depths to the boundary (approximately 100m contour line) with a cell area of 100000 m$^2$ (lateral accuracy 445 m).
    3847}
    3948  \label{fig:onslow_area}
  • production/onslow_2006/report/damage.tex

    r3397 r3402  
    1111residential collapse vulnerability models and casualty models were developed.
    1212The vulnerability models have been developed for
    13 framed residential construction using data from the Indian Ocean tsunami event. The models predict the collapse
     13framed residential construction based on limited data found in the literature
     14as well as observations from the Indian Ocean tsunami event.
     15The models predict the collapse
    1416probability for an exposed population and incorporates the following
    15 parameters known to influence building damage \cite{papathoma:vulnerability},
     17parameters thought to influence building damage \cite{papathoma:vulnerability},
    1618
    1719\begin{itemize}
     
    4143and the injury categories are presented in Table \ref{table:injury}.
    4244Input data comprised of resident population data at census
    43 district level derived from the ABS 2001 Census.
     45district level derived from the ABS 2001 Census. Give the exposure database is
     46based on residential structures, we assume that the
     47population are at home and sleeping when the event occurs and that there is no
     48warning. Therefore, the casualty estimates would be significantly different
     49if the event were to occur during the day when people are at work, travelling
     50in a vehicle, spending time on the beach, for example, or if the event occurred
     51during a major holiday season.
    4452
    4553There are an estimated
     
    5260of \$71M. Likewise, the percentage of contents loss shown is
    5361based on the total contents value of \$101M for
    54 the Onslow region.
     62the Onslow region\footnote{These values are based on 2003 figures.}.
    5563The injuries sustained is summarised in Table \ref{table:injuries}.
    5664The HAT scenario is the only scenario to cause damage
     
    6573&Inundated & Collapsed & Repair Cost
    6674& of Total Value & Losses & of Total Value \\ \hline
    67 %MSL & & 1 & \$ &   \% & \$ &  \% \\ \hline
    6875HAT & 100 &2&\$8M & 11\%&\$16M & \%16 \\ \hline
    69 %LAT & & & & & & \\ \hline
     76MSL & & 1 & \$ &   \% & \$ &  \% \\ \hline
     77LAT & & & & & & \\ \hline
    7078\end{tabular}
    7179\end{center}
     
    7886\begin{tabular}{|l|l|l|l|l|l|}\hline
    7987&Minor & Moderate & Serious & Fatal \\ \hline
    80 #MSL & &  &  & \\ \hline
    81 HAT & > 50 & < 50 & < 50 & < 50 \\ \hline
    82 #LAT & & & & \\ \hline
     88HAT & 10's & 10's & 10's & 10's \\ \hline
     89MSL & &  &  & \\ \hline
     90LAT & & & & \\ \hline
    8391\end{tabular}
    8492\end{center}
     
    8694
    8795Tsunami impact on indigeneous communities should be considered
    88 especially as a number of communities exist in coastal regions of north west WA.
     96in the future as a number of communities exist in coastal regions of north west WA.
    8997These communities are typically not included in national residential databases
    9098and would be therefore overlooked in damage model estimates.
  • production/onslow_2006/report/data.tex

    r3390 r3402  
    1 The calculated run-up height and resulting inundation ashore is determined by
     1The calculated run-up height and resulting inundation ashore is controlled by
    22the input topographic and bathymetric elevation, the
    33initial and boundary conditions, as well as the cell area of the computational
    44mesh.
    5 Ideally, the data should adequately capture all complex features
     5Ideally, the topographic and bathymetric data
     6should adequately capture all complex features
    67of the underlying bathymetry and topography. Any limitations
    78in the resolution and accuracy of the data will introduce
     
    1415and Lowest Astronomical Tide (LAT) defined as 1.5m AHD
    1516and -1.5m AHD respectively for Onslow \cite{antt:06}.
    16 These values are tidal
    17 predictions based on continous tidal observations from Standard Ports
    18 over a period of
    19 at least one year, with the Australian Hydrographic Service
    20 recommending this be extended to three years to capture
    21 changes to the mean sea level. Onslow is listed as
    22 a Standard Port. As an aside, current work at GA is
     17As an aside, current work at GA is
    2318extracting information from LANDSAT imagery to reconstruct the
    2419tidal variations for various WA locations. Future modelling of
     
    3631DLI data is distorted by vegetation and buildings. 
    3732
     33With respect to the offshore data, the Department of Planning and
     34Infrastructure (DPI) have provided state digital fairsheet data around
     35Onslow. This data covers a very small geographic area.
     36Similar data have been provided by DPI for Pt Hedland and Broome.
     37The Australian Hydrographic Office (AHO) has supplied extensive
     38fairsheet data which has also been utilised. In contrast to the onshore data,
     39the offshore data is a series of survey points which is typically
     40not supplied on a fixed grid. In addition, offshore data typically
     41does not have the coverage of the onshore data, and often the
     42offshore data will have gaps where surveys have not been conducted.
     43The coastline has been generated by
     44using the aerial photography, two detailed surveys provided
     45by WA DPI and a number of total station surveys \footnote{Total station survey information
     46has been used to verify the elevation data. A total station is an
     47electronic device that combines the ability to measure a position
     48horizontally and vertically at the same time.} of Onslow.
     49The WA DLI data surrounding the coast are error prone and
     50have been clipped at the derived coastline.
     51
    3852Figure \ref{fig:contours_compare}(a) shows the contour lines for
    3953HAT, MSL and LAT for Onslow using the DTED data where it is evident
     
    4155parts of Onslow town appears to be inundated at HAT before a tsunami has
    4256even been generated. This is due to
    43 short comings with the digital elevation model (DEM) created from
     57shortcomings with the digital elevation model (DEM) created from
    4458the DTED data.
    4559Figure \ref{fig:contours_compare}(b) shows
    4660the contour lines for HAT, MSL and LAT for Onslow using the WA DLI data.
    4761It is obvious that there are significant differences in each DEM with
    48 total station survey information and the knowledge
     62the total station survey information and the knowledge
    4963of the HAT contour line pointing to increased confidence in the WA DLI
    5064data over the DTED data for use in the inundation modelling.
    51 The impact difference based on these two onshore data sets
    52 will be discussed in Section \ref{sec:issues}.
     65Consequently the DLI data has been used in this study.
    5366
    5467
     
    7588\end{figure}
    7689
    77 With respect to the offshore data, the Department of Planning and
    78 Infrastructure (DPI) have provided state digital fairsheet data around
    79 Onslow. This data cover only a very small geographic area. (Note,
    80 similar data have been provided by DPI for Pt Hedland and Broome.)
    81 The Australian Hydrographic Office (AHO) has supplied extensive
    82 fairsheet data which has also been utilised. In contrast to the onshore data, the offshore data is a series of survey points which is typically not supplied on a fixed grid. In addition, offshore data typically does not have the coverage of the onshore data, and often the offshore data will have gaps where surveys have not been conducted.
    83 The coastline has been generated by
    84 using the aerial photography, two detailed surveys provided
    85 by WA DPI and a number of total station surveys of Onslow.
    86 The WA DLI data surrounding the coast are error prone and
    87 have been clipped at the derived coastline.
     90
    8891Appendix \ref{sec:metadata} provides more details and the supporting metadata
    8992for this study, including images of the data extent.
     
    9598\begin{center}
    9699\begin{tabular}{|l|l|}\hline
    97 Data & Detail \\ \hline
     100Data & Specifications \\ \hline
    98101DIGO DTED Level 2  & Onshore, 1 second $\approx$ 30m \\ \hline
    99102DLI & Onshore, 20m DEM and orthophotography \\ \hline
  • production/onslow_2006/report/execsum.tex

    r3389 r3402  
    22(FESA) as part of the Collaborative Research Agreement (CRA)
    33with Geoscience Australia (GA).
    4 FESA recognises the potential vulnerability of the Western Australia
    5 coastline to tsunamigenic earthquakes originating from
    6 the Sunda Arc subduction zone that caused the December 2004 event.
    7 There is historic evidence of tsunami events affecting the
     4FESA has recognised the potential vulnerability of the Western Australia
     5coastline to tsunami originating from earthquakes on
     6the Sunda Arc subduction zone.
     7There is historic evidence of tsunami affecting the
    88Western Australia coastline, \cite{CB:ausgeo},
    99and FESA has sought to assess
     
    1111threat and develop detailed response plans for a range of plausible events.
    1212
    13 This report describes the modelling methodology and first results
    14 for a particular tsunami-genic event as it impacts the Onslow township
     13This report describes the modelling methodology and initial results
     14for a specific tsunami-genic event as it impacts the Onslow township
    1515and its surrounds. Future studies
    1616will present a series of scenarios for a range of return periods to
     
    1818This report and the decision support tool are the
    1919June 2006 deliverables of the Collaborative Research Agreement
    20 between FESA and GA.
     20between FESA and GA, Tsunami Impact Modelling for WA .
    2121
  • production/onslow_2006/report/introduction.tex

    r3375 r3402  
    1 The Fire and Emergency Services Authority of Western Australia (FESA) and
     1The Fire and Emergency Services Authority (FESA) of Western Australia and
    22associated volunteers respond to a wide range of emergencies
    33as well as undertaking search and rescue operations on land and
    44water\footnote{http://www.fesa.wa.gov.au/internet/}.
     5FESA helps the West Australian
     6community prepare, prevent (where possible) and respond safely to disasters.
    57FESA also aims to reduce injury, loss of life and destruction of property in
    68Western Australian communities through proactive measures.
    7 FESA helps the West Australian
    8 community prepare, prevent (where possible) and respond safely to disasters.
    9 These risk mitigation activities involve understanding the relative risk
     9These measures involve understanding the relative risk
    1010of the disaster so that resources can be directed to appropriate areas
    1111and corresponding evacuation plans put in place. 
     
    2424This report is the first in a series of tsunami assessments
    2525of the North West Shelf. The scenario used for this study has
    26 an unknown return period, but considered a plausible event (see
     26an unknown return period, but is considered a plausible event (see
    2727Section \ref{sec:tsunamiscenario}).
    2828Subsequent assessments will use refined hazard models with
    29 associate return rates for other localities, as advised by FESA.
     29associate return periods. A suite of assessments will be
     30made for Onslow and other localities, as advised by FESA.
    3031
    3132Onslow has a population of around 800 and
     
    3738
    3839The modelling technique to simulate the
    39 impact ashore will be discussed in Section \ref{sec:anuga} and data inputs
     40impact ashore is discussed in Section \ref{sec:methodology} and data inputs
    4041discussed in Section \ref{sec:data}.
    4142The inundation results are presented and discussed in Section \ref{sec:results}
  • production/onslow_2006/report/modelling_methodology.tex

    r3390 r3402  
    33by a range of rapid onset natural hazards. Through the integration of natural hazard research, defining national exposure and
    44estimating socio-economic vulnerabilities, predictions of the likely impacts of events can be made.
    5 Hazards include earthquakes, landslides, tsunami, severe winds and cyclones.
    6 
    75By modelling the likely impacts on urban communities as accurately as possible and
    86building these estimates into land use planning and emergency
     
    2826The hazard itself is then reported as a maximum wave height at a fixed contour line near the coastline,
    2927(e.g. 50m). This is how the preliminary tsunami hazard assessment was reported by GA
    30 to FESA in September 2005 \cite{BC:FESA}. The assessment used the Method of Splitting Tsunamis (MOST)
     28to FESA in September 2005 \cite{BC:FESA} for a suite of Mw 9 earthquakes
     29evenly spaced along the Sunda Arc subduction zone.
     30The assessment used the Method of Splitting Tsunamis (MOST)
    3131\cite{VT:MOST} model.
    3232%The maximal wave height at a fixed contour line near the coastline
     
    6060
    6161\bigskip %FIXME (Ole): Should this be a subsection even?
    62 The risk of the scenario tsunami event cannot be determined until the
    63 likelihood of the event is known. GA is currently building a
     62The risk of a given tsunami scenario cannot be determined until the
     63likelihood of the tsunami is known. GA is currently building a
    6464complete probabilistic hazard map which is due for completion
    6565in late 2006. We therefore report on the impact of a single
     
    6767will be assessed for a range of events which will ultimately
    6868determine a tsunami risk assessment for the NW shelf.
     69
     70FESA is interested in the ``most frequent worst case scenario''. Whilst
     71we currently cannot determine exactly what that event may be, the
     72preliminary hazard assessment suggested that the maximum
     73magnitude of earthquakes off Java was considered to be at
     74least 8.5 and could potentially be as high as 9. Therefore,
     75the Mw 9 event
     76provides a plausible worst case scenario and is used as the tsunami
     77source in this report.
     78Figure \ref{fig:mw9} shows the maximum wave height of a tsunami initiated
     79by a Mw 9 event off
     80the coast of Java. This event provides the source and
     81boundary condition to the
     82inundation model presented in Section \ref{sec:anuga}.
     83
     84\begin{figure}[hbt]
     85
     86  \centerline{ \includegraphics[width=140mm, height=100mm]
     87{../report_figures/mw9.jpg}}
     88
     89  \caption{Maximum wave height (in cms) for a Mw 9 event off the
     90coast of Java}
     91  \label{fig:mw9}
     92\end{figure}
     93
    6994%To model the
    7095%details of tsunami inundation of a community one must therefore capture %what is
  • production/onslow_2006/report/summary.tex

    r3396 r3402  
    33occurring at Highest Astronomical Tide, Lowest Astronomical Tide
    44and Mean Sea Level.
    5 There is no knowledge of the return period for this event. The
     5As yet, there is no knowledge of the return period for this event. The
    66modelling methodology, assumptions and data sources for the Onslow
    77scenario have also been described.
  • production/onslow_2006/report/tsunami_scenario.tex

    r3375 r3402  
    3333\begin{figure}[hbt]
    3434
    35   \centerline{ \includegraphics[width=100mm, height=75mm]
     35  \centerline{ \includegraphics[width=140mm, height=100mm]
    3636{../report_figures/mw9.jpg}}
    3737
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