Edgecumbe-Rangitaiki Plains Flood Mitigation Project

In July 2004 a 100 yr flood in the Rangitaiki River breached the main river stopbank upstream of Edgecumbe. Water overwhelmed the Reids Floodway and flooded 17,000 ha of farmland. Parts of eastern Edgecumbe were extensively flooded, the main Transpower substation isolated, State Highway 2 washed out and the Fonterra dairy factory flooded. Localised stormwater from heavy rain caused extensive surface flooding to the west of Edgecumbe.

Bay of Plenty Regional Council (BOPRC) and Whakatane District Council approached Central government for assistance and were invited to submit a joint business case with proposed solutions to mitigate flood risk. Studies identified a range of measures as being required including strengthening of stopbanks, increased flood pumping, localised stopbank raising to preferentially protect urban areas and key infrastructure and a doubling of floodway capacity. A particular feature of the area is the alluvial pumiceous soils which provide poor foundation conditions for stopbanks.

The first phase of the works is now substantially complete. This paper describes the features of the area, the works completed to date and those remaining. The joint cooperative approach of Central Government, Regional Council, District Council, community and key infrastructure owners to produce a comprehensive solution is discussed.