PLANNING AND DESIGN OF URBAN RIVER RESTORATION IN A STEEP, COASTAL NEW ZEALAND CATCHMENT

New Zealand is known throughout the world as a “clean and green” country with pristine coastal, mountain, and rural landscapes. In the few urban areas of the country, however, many rivers and streams have been extensively modified through channelization for flood control, impacted by stormwater and nonpoint source pollution, and kept separate from urban populations. Only recently has restoration of both urban and rural rivers been a focus of the government, scientists, engineers, and environmental/community groups. Great strides have been made in the past few years on river restoration in some very unique and challenging environments.The Otago Regional Council is a local government agency in the Otago Region of the South Island of New Zealand charged with management of natural resources, including river management. This agency has developed and implemented a comprehensive urban stream restoration program in Dunedin, the largest city in the region on the southeast coast of the South Island. The Water of Leith, the primary river flowing through the city, has been the focus of a significant amount of restoration planning, design, and implementation. Planning and design was performed for a pilot or demonstration reach in the city center than included some unique elements as well as many issues that are common to urban stream restoration projects. The lower reaches of the creek are highly channelized and the catchment is steep with a short time of concentration, high potential for debris flows, floodplain encroachment, and significant flood risks.The work performed and discussed in this paper includes community consultation/involvement and coordination with stakeholders, modeling and analysis of catchment hydrology, hydraulic modeling and flood risk evaluation, evaluation of the fluvial geomorphology of the river, analysis of water quality and aquatic ecology, feasibility studies and planning, and preliminary design to optimize multiple restoration objectives. The work on the Water of Leith is an good case study of issues and requirements for planning and design of urban stream restoration in a challenging physical and socioeconomic environment that should be considered in a range of types of restoration projects.