Abstract
Christchurch city’s primary natural hazard exposure, arguably, is to various kinds of flooding and inundation. Recently the Canterbury Earthquake Sequence (CES) reshaped many aspects of the city’s natural and built environment, with significant changes to the flood-scape. In response to the CES impacts on the city’s waterways and drainage network, the Christchurch City Council (CCC) established the Land Drainage Recovery Programme (LDRP) to consider these impacts on flood risk, and to identify and implement responses to reduce these risks.Cited on a low-lying coastal plain in a seismically active setting, large parts of the city are subject to the effects of, and interactions between, multiple types of natural hazard, with a particular concentration of multi-hazard risk in coastal and riverside areas. This challenging circumstance gives rise to the question: <em>How do we make decisions about flood management in a multi-hazard environment? To address this question, the Council initiated an investigation that aims to develop flood management plans for eastern Christchurch involving a range of sustainable, adaptable and resilient flood management options within a multi -hazard context. The hazards examined in this assessment included fluvial, pluvial and coastal flooding; the likely impacts of climate change on these including the impacts of sea level rise on coastal inundation, erosion and rising groundwater; and the potential cascading effects of future earthquakes (subsidence, liquefaction, lateral spread, ground shaking) and tsunami on flooding risks. The assessment approach employed involves three stages: (i) understanding the multiple hazards and multi-hazard interactions affecting the city’s exposure to flood risks in terms of spatial co-location, temporal coincidence and cascading impacts; (ii) undertaking targeted studies to address key gaps in our understanding of these multiple hazards; and (iii) developing a range of potential management options including engineering, planning and policy responses, within an adaptive planning pathways framework. Stage one has been completed, the stage two studies have largely been completed, and considerable work effort is being undertaken to address the challenges in proceeding to stage three of the study. This presentation overviews the overall approach of the project and presents the findings of the stage one analysis of multi-hazard interactions.