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Probabilistic assessment of increased flooding vulnerability in Christchurch city after the Canterbury 2010-2011 Earthquake Sequence, New Zealand
| Content Provider | Semantic Scholar |
|---|---|
| Author | Cavalieri, Francesco Franchin, Paolo Ko, Su Young Giovinazzi, Sonia Hart, Deirdre E. |
| Copyright Year | 2015 |
| Abstract | Major earthquakes can extensively transform the above and below ground natural and built environments of cities, leading to decreased drainage system capacity and, ultimately, to Increased Flooding Vulnerability (IFV). This has been the case for Christchurch city in New Zealand, which experienced the 2010 to 2011 Canterbury Earthquake Sequence (CES). These seismic events were followed by extreme rainfall in March-April 2014, with much of the city experiencing damaging flooding. This paper uses data from a Christchurch case study to extend a recently-developed infrastructure damage simulation tool to the probabilistic assessment of earthquake-altered flood risk in a built environment. In particular, the focus is on the IFV caused by the earthquake-induced damage to the pipeline component of Christchurch's storm water system, which was analysed at both connectivity and capacity levels. The probabilistic analysis was carried out via a plain Monte Carlo simulation, enabling the uncertainty affecting several key parameters to be taken into account. Final analysis results are presented spatially and in the form of cumulative distribution of flood height, the latter being an impact metric of great interest for infrastructure owners and emergency managers. INTRODUCTION High magnitude earthquakes can significantly alter urban land and built environments, with effects such as ground subsidence and uplift, alterations of river channel capacity, slope and elevation, and damage to storm water systems. The altered urban environment may be exposed to Increased Flooding Vulnerability (IFV), including a higher probability for Critical Infrastructure (CI) systems such as buildings and lifelines to suffer greater flood depths and/or extents in response to future rainfall events compared to pre-quake scenarios. The case study city, Christchurch, New Zealand, was hit by the Canterbury Earthquake Sequence (CES), a series of strong earthquakes between September 2010 12 International Conference on Applications of Statistics and Probability in Civil Engineering, ICASP12 Vancouver, Canada, July 12-15, 2015 2 and December 2011 (Hughes at al., 2015). The IFV phenomenon post the CES was revealed when the city experienced extreme flooding across large areas in August 2012, June 2013 and March-April 2014 (EQC, 2014; Christensen and Gillooly, 2014; Allen et al., 2014), due to three flooding mechanisms: pluvial, fluvial and tidal (Fisher et al., 2014). Published literature to date features few studies of IFV following significant earthquakes (e.g. Hughes at al., 2015; Tonkin & Taylor, 2014b). The goal of this paper is to provide another contribution to this emerging research field. The paper presents an extension of a recently developed civil infrastructure simulation tool, namely Object-Oriented Framework for Infrastructure Modelling and Simulation (OOFIMS, 2010-2014) (see details in Franchin, 2014), to the probabilistic assessment of the earthquake-altered flooding risk on the built environment. The paper focuses, in particular, on IFV caused by the earthquake-induced damage to the pipeline component of the storm water system. The case study area was identified as the part of Christchurch that experienced flooding mainly due to storm water overflow during the March-April 2014 events. Final analysis results are presented in terms of flood height, an impact metric that is of great interest to infrastructure owners and emergency managers, since it can be easily correlated to network performance metrics, such as road functionality levels (open, open for emergency, closed). 1. CHRISTCHURCH STORM WATER PIPELINE NETWORK Figure 1a) shows the Christchurch's storm water pipeline network (light grey) as well as the subcatchments' boundaries (dark grey). The system is made up of a number of hydraulic pieces of equipment, including: 1) pipelines (which can be gravity or pressure); 2) manholes (for maintenance access and replacements); 3) sumps (where ground/road surface water discharges into a pipeline); 4) pipe outfall structures or discharge locations (where a pipeline discharges into an open waterway, such as the Heathcote River, Avon River and Avon-Heatcote Estuary), with flap gates at the outlets. Figure 1: a) Christchurch storm water pipeline network (sketched in light grey) and sub-catchments' boundaries (dark grey); the Heathcote and Avon rivers are also indicated in blue. b) Close-up on the network portion inside the selected sub-catchment. If seen as a tree-like graph, the network consists of around 64,600 circular section pipes and 71,600 nodes. The diameters of most pipes range from 100 to 375 mm, while about 16% of the pipes have sizes in the 400 to 3000 mm range. The most common materials used for pipes are the following: Rubber Ring Joint Reinforced Concrete (RRJRC); Concrete (CONC); Asbestos Cement (AC); Corrugated Aluminium (AL); Cement Lined Steel (CLS); Cast Iron (CI); Polyvinyl Chloride (PVC), Modified Polyvinyl Chloride (mPVC), and Unplasticized Polyvinyl Chloride (uPVC); Polyethylene (PE) and High Density Polyethylene (HDPE). Other materials used are Earthenware (EW), Brick Barrel (BB), Cured In Place Pipe (CIPP) liner, Vitrified Clay Pipe (VCP) and galvanized corrugated metal (CORRGALV). a) |
| File Format | PDF HTM / HTML |
| DOI | 10.14288/1.0076154 |
| Alternate Webpage(s) | https://open.library.ubc.ca/media/download/pdf/53032/1.0076154/2 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
