1 | |
---|
2 | %This section deals with impact modelling which covers damage |
---|
3 | %modelling and economic impact analysis. |
---|
4 | In this report, impact modelling refers to damage as a result |
---|
5 | of the inundation described in Section \ref{sec:results}. This damage |
---|
6 | is reported as damage to infrastructure as well as |
---|
7 | number of human injuries and is determined assuming |
---|
8 | that the event occurs at night. The infrastructure |
---|
9 | refers to residential structures only and is sourced from the |
---|
10 | the National Building Exposure Database (NBED). The NBED has been |
---|
11 | created by Geoscience Australia so that consistent risk assessments for a range |
---|
12 | of natural hazards can be |
---|
13 | conducted\footnote{http://www.ga.gov.au/urban/projects/ramp/NBED.jsp}. |
---|
14 | It contains information |
---|
15 | about residential buildings, people, infrastructure, |
---|
16 | structure value and building contents. |
---|
17 | From this database, we find that there |
---|
18 | are 325 residential structures and a population of approximately 770 |
---|
19 | in Onslow\footnote{Population is determined by census data and an ABS |
---|
20 | housing survey}. |
---|
21 | |
---|
22 | |
---|
23 | To develop building damage and casuality estimates, we briefly describe |
---|
24 | residential collapse probability models and casualty models and their |
---|
25 | application to inundation modelling. There is limited data found in |
---|
26 | the international literature to support the development of |
---|
27 | vulnerability models. However, |
---|
28 | with reported observations made of building performance during the |
---|
29 | recent Indian Ocean tsunami, vulnerability models have been proposed for |
---|
30 | framed residential construction. The models predict the collapse |
---|
31 | probability for an exposed population and incorporate the following |
---|
32 | parameters known to influence building damage \cite{papathoma:vulnerability}, |
---|
33 | |
---|
34 | \begin{itemize} |
---|
35 | \item inundation depth at building |
---|
36 | \item building row from coast |
---|
37 | \item building material (residential framed construction) |
---|
38 | \item inundation depth at house above floor level |
---|
39 | \end{itemize} |
---|
40 | |
---|
41 | The collapse vulnerability models used are presented in Table \ref{table:collapse}. |
---|
42 | In applying the model all structures in the inundation zone were |
---|
43 | spatially located and the local water depth and building row |
---|
44 | number from the exposed edge of the suburb were determined for each. |
---|
45 | |
---|
46 | Casualty models were developed by making reference to the |
---|
47 | storm surge models used for the Cairns Cyclone Scenario and |
---|
48 | through consultation with Dr David Cooper of NSW Health, \cite{cooper:2005}. |
---|
49 | The injury probabilities for exposed populations were selected |
---|
50 | based on the nocturnal nature of the event, the collapse outcome |
---|
51 | for the structure, the water depth with respect to |
---|
52 | sleeping height (1.0 m) and the limited warning noise for people |
---|
53 | in the first three city blocks (six house rows) that could potentially |
---|
54 | awaken them. The three injury categories correspond with the |
---|
55 | categories presented in HAZUS-MH \cite{NIBS:2003} for earthquake |
---|
56 | related injury. The casualty model used is presented in Table |
---|
57 | \ref{table:casualty} |
---|
58 | and the injury categories are presented in Table \ref{table:injury}. |
---|
59 | Input data comprised of resident population data at census |
---|
60 | district level derived from the ABS 2001 census. |
---|
61 | |
---|
62 | The damage to the residential structures in the Onslow community |
---|
63 | is summarised in Table \ref{table:damageoutput}. The percentage |
---|
64 | of repair cost to structural value shown is based on the total structural value |
---|
65 | of \$60,187,955. Likewise, the percentage of contents loss shown is |
---|
66 | based on the total contents value of \$85,410,060 for |
---|
67 | the Onslow region. The injuries sustained is summarised |
---|
68 | in Table \ref{table:injuries} with around \% affected in the 0m AHD |
---|
69 | scenario. |
---|
70 | Around \% |
---|
71 | of the population are affected in the 1.5m AHD scenario with around \% |
---|
72 | affected in the 0m AHD scenario. |
---|
73 | |
---|
74 | |
---|
75 | \begin{table}[h] |
---|
76 | \begin{center} |
---|
77 | \caption{Residential damage sustained for the MSL, HAT and LAT scenarios.} |
---|
78 | \label{table:damageoutput} |
---|
79 | \begin{tabular}{|l|l|l|l|l|l|l|}\hline |
---|
80 | &Houses & Houses & Structural & Repair Cost \% & Contents & Contents Loss \% \\ |
---|
81 | &Inundated & Collapsed & Repair Cost |
---|
82 | & of Total Value & Losses & of Total Value \\ \hline |
---|
83 | MSL & & 1 & \$ & \% & \$ & \% \\ \hline |
---|
84 | HAT & & & & & & \\ \hline |
---|
85 | LAT & & & & & & \\ \hline |
---|
86 | \end{tabular} |
---|
87 | \end{center} |
---|
88 | \end{table} |
---|
89 | |
---|
90 | \begin{table}[h] |
---|
91 | \begin{center} |
---|
92 | \caption{Injuries sustained for the MSL, HAT and LAT scenarios.} |
---|
93 | \label{table:injuries} |
---|
94 | \begin{tabular}{|l|l|l|l|l|l|}\hline |
---|
95 | &Minor & Moderate & Serious & Fatal \\ \hline |
---|
96 | MSL & & & & \\ \hline |
---|
97 | HAT & & & & \\ \hline |
---|
98 | LAT & & & & \\ \hline |
---|
99 | \end{tabular} |
---|
100 | \end{center} |
---|
101 | \end{table} |
---|
102 | |
---|
103 | Impact on indigeneous communities are important considerations when determining |
---|
104 | tsunami impact, especially as a number of communities exist in coastal regions. |
---|
105 | These communities are typically not included in national residential databases |
---|
106 | and would be therefore overlooked in damage model estimates. |
---|
107 | There is one indigeneous community located in this study area as seen |
---|
108 | in Figure |
---|
109 | \ref{fig:points}. The population of the Bindibindi community is 140 |
---|
110 | (18 \% of the Onslow population) |
---|
111 | and is situated close to the coast as seen in Figure \ref{fig:points}. |
---|
112 | During the HAT scenario, |
---|
113 | over 1m of water will inundate parts of the community (Figure |
---|
114 | \ref{fig:gaugeBindiBindiCommunity}) causing significant damage. |
---|