ORC pursues principled pro-active flood management in district planning

The effects of more intensive land use and building are important considerations in developing a long-term approach to flood management in the lower Silver Stream catchment near Mosgiel.

This has been highlighted in a set of management principles endorsed by councillors at a meeting of the Otago Regional Council (ORC) engineering and hazards committee this week.

The principles highlight that District Plan land use control within Dunedin city should allow for active flood risk mitigation, ensuring further development on the flood plain does not aggravate or increase flood risk.

The committee has asked staff to investigate options for a possible change to the district plan, which could propose specific flood mitigation measures for the lower Taieri River, including risk-related zoning.

The principles, developed by ORC staff, suggest that a long-term approach to managing flood hazard risk in the Taieri catchment needs to consider the effects of repeat flood events, and the risks faced by land owners and occupiers.

They also suggest areas which are less likely to be affected by flooding should be given preference in the district plan to allow new development over areas which are at greatest risk.

ORC engineering and hazards committee chairman Cr Stephen Woodhead, said "We cannot continue to allow land use of any type to aggravate the flood risk in the Taieri."

ORC director of environmental engineering and natural hazards Gavin Palmer said the lower Silver Stream catchment incorporated a variety of land uses including residential, rural residential, and pastoral farming.

"Some of that land use is exposed to one or more flood hazards, including the Silver Stream, the hill catchments to the north-east, and south; internal run-off; and the Taieri River," Dr Palmer said.

The expansion of urban land use through the creation and development of lifestyle blocks was increasing the overall flood risk for the area as that development spread onto flood-prone land.

This was highlighted during the flood of April 2006, and to a lesser degree during a similar event in July 2007, Dr Palmer said.