Changeset 3480


Ignore:
Timestamp:
Aug 10, 2006, 10:55:53 AM (18 years ago)
Author:
sexton
Message:

investigating pt hedland simulations

Location:
production/pt_hedland_2006
Files:
79 added
2 edited

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  • production/pt_hedland_2006/report/data.tex

    r3394 r3480  
    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
    … …  
    99made within the model.
    1010
    11 As part of the CRA, it was decided to provide results for the
    12 extremes of the tidal regimes to understand the potential range of impacts
    13 from the event. In this study, we used the Australian Height Datum (AHD)
     11In this study, we used the Australian Height Datum (AHD)
    1412as the vertical datum. Mean Sea Level (MSL) is approximately equal to
    15130m AHD with the Highest Astronomical Tide (HAT)
    16 and Lowest Astronomical Tide (LAT) defined as 3.6m AHD
    17 and -3.9m AHD respectively for Port Hedland \cite{antt:06}.
    18 These values are tidal
    19 predictions based on continous tidal observations from Standard Ports
    20 over a period of
    21 at least one year, with the Australian Hydrographic Service
    22 recommending this be extended to three years to capture
    23 changes to the mean sea level. Onslow is listed as
    24 a Standard Port. As an aside, current work at GA is
     14and Lowest Astronomical Tide (LAT) defined as 3.6 m AHD
     15and -3.9 m AHD respectively for Port Hedland \cite{antt:06}.
     16As an aside, current work at GA is
    2517extracting information from LANDSAT imagery to reconstruct the
    2618tidal variations for various WA locations. Future modelling of
    … …  
    3830the DLI data is distorted by vegetation and buildings. 
    3931
     32With respect to the offshore data, the Department of Planning and
     33Infrastructure (DPI) have provided state digital fairsheet data around
     34Onslow. This data covers a very small geographic area.
     35Similar data have been provided by DPI for Pt Hedland and Broome.
     36The Australian Hydrographic Office (AHO) has supplied extensive
     37fairsheet data which has also been utilised. In contrast to the onshore data,
     38the offshore data is a series of survey points which is typically
     39not supplied on a fixed grid. In addition, offshore data typically
     40does not have the coverage of the onshore data, and often the
     41offshore data will have gaps where surveys have not been conducted.
     42The coastline has been generated by
     43using the aerial photography, two detailed surveys provided
     44by WA DPI and a number of total station surveys \footnote{Total station survey information
     45has been used to verify the elevation data. A total station is an
     46electronic device that combines the ability to measure a position
     47horizontally and vertically at the same time.} of Onslow.
     48The WA DLI data surrounding the coast are error prone and
     49have been clipped at the derived coastline.
     50
    4051Figure \ref{fig:contours_compare}(a) shows the contour lines for
    4152HAT, MSL and LAT for Port Hedland using the DTED data where it is evident
    42 that the extent of the tidal inundation is exaggerated.
    43 In particular,
    44 parts of Port Hedland appear to be inundated at HAT before a tsunami has
    45 even been generated.
    46 This is due to
    47 short comings with the digital elevation model (DEM) created from
     53that the extent of the tidal inundation is exaggerated. In particular,
     54parts of Port Hedland appears to be inundated at HAT before a tsunami has
     55even been generated. This is due to
     56shortcomings with the digital elevation model (DEM) created from
    4857the DTED data.
    4958Figure \ref{fig:contours_compare}(b) shows
    5059the contour lines for HAT, MSL and LAT for Port Hedland using the WA DLI data.
    5160It is obvious that there are significant differences in each DEM with
    52 total station survey information and the knowledge
     61the knowledge
    5362of the HAT contour line pointing to increased confidence in the WA DLI
    5463data over the DTED data for use in the inundation modelling.
    55 The impact difference based on these two onshore data sets
    56 will be discussed in Section \ref{sec:issues}.
     64Consequently the DLI data has been used in this study.
    5765
    5866
    … …  
    7987\end{figure}
    8088
    81 With respect to the offshore data, the Department of Planning and
    82 Infrastructure (DPI) have provided state digital fairsheet data around
    83 Port Hedland. This data cover only a very small geographic area. (Note,
    84 similar data have been provided by DPI for Onslow and Broome.)
    85 The Australian Hydrographic Office (AHO) has supplied extensive
    86 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.
    87 The coastline has been generated by
    88 using the aerial photography and two detailed surveys provided
    89 by WA DPI.
    90 The WA DLI data surrounding the coast are error prone and
    91 have been clipped at the derived coastline.
     89
    9290Appendix \ref{sec:metadata} provides more details and the supporting metadata
    9391for this study, including images of the data extent.
    94 Table \ref{table:data} summarises the available data. 
     92Table \ref{table:data} summarises the available data.
    9593
    9694\begin{table}
    … …  
    111109\pagebreak
    112110
    113 
    114 
    115 

  • production/pt_hedland_2006/report/summary.tex

    r3375 r3480  
    1 This report has described the impact on Port Hedland from a tsunami
     1This report has described the impact to Port Hedland from a tsunami
    22generated by a Mw 9 earthquake on the Sunda Arc subduction zone
    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
    6 modelling methodology, assumptions and data sources for the Onslow
     5As yet, there is no knowledge of the return period for this event. The
     6modelling methodology, assumptions and data sources for the Port Hedland
    77scenario have also been described.
    8 As discussed in Section \ref{sec:issues}, it is imperative
     8
     9As shown in Section \ref{sec:data}, it is imperative
    910that the best available data is used to increase confidence
    10 in the inundation maps. An onshore grid resolution of the order
     11in the inundation maps.
     12Given that the Highest Astronomical Tide contour
     13line is further from the coast for the DTED data than the DLI data, we
     14expect the inundation to extend further and thus be greater than
     15that seen in Figure \ref{fig:MSL_max_inundation}.
     16The impact modelling
     17will result in significantly inflated structural and contents loss figures as well as
     18numbers of people affected.
     19These results strongly point to the need for the best
     20available data so that more accurate predictions regarding the
     21inundation can be made.
     22An onshore grid resolution of the order
    1123of tens of metres is required, however, it is more important that the data
    1224are accurate (or at least well known).
     25
    1326These scenarios will be revisited once the probabilistic models
    1427are complete so that a suite of tsunami impact assessments can be made.
    15 
    1628Future activities to support the impact studies on the North West Shelf
    1729include:
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