1 | %As part of the CRA, it was decided to provide results for the |
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2 | %extremes of the tidal regimes to understand the potential range of impacts |
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3 | %from the event. The Highest Astronomical Tide (HAT) and Lowest |
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4 | %Astronomical Tide (LAT) are defined as 1.5m AHD and -1.5m AHD |
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5 | %respectively for Onslow, \cite{antt:06}. These values are tidal |
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6 | %predictions based on continous tidal observations from Standard Ports |
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7 | %over a period of |
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8 | %at least one year, with the Australian Hydrographic Service |
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9 | %recommending this be extended to three years to capture |
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10 | %changes to the mean sea level. Onslow is listed as |
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11 | %a Standard Port. |
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12 | |
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13 | %As an aside, current work at GA is |
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14 | %extracting information from LANDSAT imagery to reconstruct the |
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15 | %tidal variations for various WA locations. Future modelling of |
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16 | %these areas will incorporate this information. |
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17 | |
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18 | Initial simulations for this study used the DIGO DTED Level 2 data |
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19 | (see Section \ref{sec:data}) due to the fact it is |
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20 | ``bare earth'', whereas the DLI data is distorted by |
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21 | vegetation and buildings. |
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22 | Figure \ref{fig:contours_compare} shows the contour lines for |
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23 | HAT, MSL and LAT for Onslow using the DTED data where it is evident |
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24 | that the extent of the tidal inundation is exaggerated. This is due to |
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25 | short comings with the digital elevation model (DEM) created from |
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26 | the DTED data. The DEM has been |
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27 | derived from 20m contour lines. {\bf Need some words from hamish here.} |
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28 | As a result, we turned to the WA DLI onshore data to present |
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29 | the results in this report. Figure \ref{fig:contours_compare} shows |
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30 | the contour lines for HAT, MSL and LAT for Onslow using the WA DLI data. |
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31 | It is obvious that there are significant differences in each DEM with |
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32 | secondary information regarding total station surveys and the knowledge |
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33 | of the HAT contour line pointing to increased confidence in the WA DLI |
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34 | data over the DTED data for use in inundation modelling. |
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35 | |
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36 | The purpose of this section then is to show the differences to the impact |
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37 | ashore when each data set is used to demonstrate the importance of using the |
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38 | best possible data set. The maximum inundation map is shown for the MSL |
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39 | scenario using the DTED data in |
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40 | Figure \ref{fig:MSL_map_DTED} which can be compared with the equivalent map for |
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41 | the WA DLI data, Figure \ref{fig:MSL_max_inundation}. Given that the 1.5m contour |
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42 | line is further from the coast for the DTED data than the DLI data, we |
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43 | expect to see the inundation to reach further and thus be greater than |
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44 | that seen in Figure \ref{fig:MSL_max_inundation}. This is confirmed by |
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45 | Figure \ref{fig:MSL_map_DTED}. These results point to the need for the best |
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46 | available data so that more accurate predictions regarding the |
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47 | inundation can be made. |
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48 | |
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49 | Additionally, we show the time history of the water's stage and |
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50 | velocity for the point locations in Table \ref{table:locations} for |
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51 | both the DTED and DLI data at MSL. These results are shown in Section |
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52 | \ref{sec:timeseriescompare}. |
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53 | \pagebreak |
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54 | |
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55 | \begin{figure}[p] |
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56 | |
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57 | \centerline{ \includegraphics[width=150mm, height=100mm] |
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58 | {../report_figures/onslow_dted_contour.jpg}} |
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59 | |
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60 | % \caption{Onslow region showing the -1.5m AHD (LAT), 0m AHD (MSL) |
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61 | %and -1.5m AHD (LAT) contour lines using the DTED Level 2 data.} |
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62 | % \label{fig:contours_dted} |
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63 | %\end{figure} |
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64 | |
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65 | %\begin{figure}[hbt] |
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66 | |
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67 | \centerline{ \includegraphics[width=150mm, height=100mm] |
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68 | {../report_figures/onslow_dli_contour.jpg}} |
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69 | |
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70 | \caption{Onslow region showing the -1.5m AHD (LAT), 0m AHD (MSL) |
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71 | and -1.5m AHD (LAT) contour lines using the DTED Level 2 data and |
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72 | the WA DLI data.} |
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73 | % \label{fig:contours_dli} |
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74 | \label{fig:contours_compare} |
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75 | \end{figure} |
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76 | |
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77 | \begin{figure}[p] |
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78 | |
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79 | \centerline{ \includegraphics[width=\paperwidth] |
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80 | {../report_figures/mid_tide_DTED.jpg}} |
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81 | |
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82 | \caption{Maximum inundation map for the Onslow region using |
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83 | the DTED data.} |
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84 | \label{fig:MSL_map_DTED} |
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85 | \end{figure} |
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86 | |
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