The flood risk in many urban catchments is poorly understood. Legacy stormwater infrastructure is often substandard and anticipated climate change induced sea level rise and increased rainfall intensity will typically exacerbate present risk. In a Department of Climate Change and Energy Efficiency (DCCEE) funded collaboration between Geoscience Australia (GA) and the City of Sydney, the impacts on the Alexandra Canal catchment in the City of Sydney local government area have been studied. This work has built upon detailed flood hazard analyses by Cardno Pty Ltd commissioned by the City of Sydney and has entailed the development of exposure and vulnerability information. Significantly, the case study has highlighted the value of robust exposure attributes and vulnerability models in the development of flood risk knowledge.
The paper describes how vulnerability knowledge developed following the 2011 Brisbane floods is extended to include key building types found in the inner suburb of Sydney. It also describes the systematic field capture of building exposure information in the catchment area and its categorisation into 19 generic building types. The assessment of ground floor heights from street view imagery using the Field Data Analysis Tool (FiDAT) developed at Geoscience Australia is also presented.
The selected hazard scenario was a 100 year Annual Recurrence Interval (ARI) event with 20% increased rainfall intensity accompanied by a 0.55m sea level rise in Botany Bay into which the stormwater infrastructure discharges. The impact from the selected scenario was assessed in terms of monetary loss for four combinations. The combinations consist of two vulnerability model suites (GA and NSW Government) and two floor height attribution methods (assumed 0.15m uniformly and evaluated from street view imagery).
It was observed that the total loss is higher in the case of assumed floor heights compared to FiDAT processed floor heights as the former failed to capture increased floor heights for newer construction. However, the loss is lower when only two vulnerability models developed by NSW Government are applied for the entire building stock in the region as two models produced a coarser modelling of the variety in the whole building stock.
Abstract & Poster presented at Floodplain Management Association National Conference 2013:
http://www.floodplainconference.com/papers2013.php
