source: production/onslow_2006/report/damage.tex @ 3339

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