In the Wake of Change: An Urban Design Response to Rising Sea Levels in Wellington City

Abstract

This thesis focuses on possible urban design responses to a worst-case scenario for sea level change: a rise of one metre by the year 2100. Wellington City is comparable to many coastal cities around the world; much of the city sits on lowlying reclaimed land. A rise in sea level of one metre could result in extensive damage to buildings and infrastructure. Scientists predict that seas will rise somewhere between 0.18m and 1.2m by the end of the century. New Zealand’s Ministry for the Environment advises local bodies to plan for a rise in sea level of at least 0.8m by the year 2090. Wellington City Council has begun to research the possible effects of sea level rise on the city but has not yet seriously considered design options in response to this. The uncertainties regarding the extent of sea level rise mean its impact on Wellington City could be minimal (0.5 m rise) or extensive (1.5m rise). Dykes, sea walls and levees have been constructed for centuries to protect local populations. These can be detrimental to urban quality, and can impede the connections between cities and their waterfronts. Up until now, their effects on overall urban design have rarely been considered. Urban designs adopted internationally for flood defence were reviewed with regard to Wellington City’s needs. A mapping study of three possible scenarios (0.5m, 1.0m, 1.5m) for sea level change in Wellington City has been made, including assessment with respect to urban design principles. This thesis concludes by offering a realistic response to the one metre scenario. Three sections of the city are developed further to demonstrate how a unified response could be developed throughout the city. The chosen response to the problem of sea level rise in Wellington City seeks to preserve sense of place while introducing new urban design concepts. The chosen design uses a sea wall to protect the existing city against a one-metre rise in sea level, and creates an amphibious zone on its seaward side. The sea wall sits inside the city rather than around it. As well as forming a boundary, it is a public structure offering visual connections between city and sea, and maintaining the essential character of the waterfront. The amphibious zone is designed to withstand flooding during storms and high sea surges. Design in this zone includes new building processes that adapt with sea level changes.