Upper Ruamāhanga River
The Ruamāhanga River system, from the Waiohine confluence upstream, has a total catchment area of 1560km². The catchment is made up of sub-catchments consisting of the Ruamāhanga above Mount Bruce, and the Waipoua and Waingawa rivers which flow from the eastern side of Tararua Range, and the Kopuaranga, Whangaehu and Taueru rivers which are sourced from the eastern Wairarapa hills.
The catchment has a history of flooding. Flooding can be dangerous and cause damage to private property and community assets.
Processes for managing flooding and erosion – through our river schemes – have been in place in the catchment for some time. Our new proposed plan takes a long term view of the whole catchment.
In 2012 the development of the Te Kāuru Upper Ruamāhanga Floodplain Management Plan began. The work is led by the Te Kāuru Upper Ruamāhanga Subcommittee, which was appointed in 2014.
We’ve gathered and reviewed information, and drafted some proposals. In July 2018, we asked for your feedback. We want to know if the Floodplain Management Plan (FMP) is heading in the right direction.
The Upper Ruamāhanga floodplain soils are formed from alluvial parent materials with two different sources. The rivers from the Tararua Ranges contribute greywacke alluvium, and the rivers sourced from the eastern Wairarapa hills contribute alluvial silts and sands eroded from mudstones, sandstones and limestones.
Different soil types have developed at various places on the floodplain depending on the rate of flood deposition, the source of material, time since deposition, and natural drainage. The natural fertility and erodibility of these soils is quite variable.
Ever since human settlement began in the Wairarapa there has been a need for people to protect themselves and their assets from the threat of flooding. This need would have grown greatly with increasing European settlement and more intensive land-uses, which has meant that protection from the harmful effects of the river has become a necessity.
During the 1930s settlers suffered damage and loss when the Ruamāhanga River overflowed its banks, washing shingle onto valuable pastures. The bed of the river had become badly choked with willows, restricting flood flows, and the channel was inadequate and of irregular alignment.
A river control scheme was implemented in 1953 and during the next 20 years achieved success in bank edge protection, river alignment, and reduced the incidence of flooding along many sections of the river.
The Upper Ruamāhanga River Control Scheme was established in 1982 and covers the length of the Ruamāhanga River from Mount Bruce downstream to the Waiohine confluence. The scheme was designed to protect an area of about 2760ha of rural land and a number of public utilities using stop banks, heavy bank protection, vegetation buffer zones and the Te Ore Ore grade-control weir. Greater Wellington is responsible for the implementation and maintenance of the scheme.
The Te Kāuru Upper Ruamāhanga River Floodplain Management Subcommittee have been working alongside the community since 2014 to create a plan for managing flooding and erosion in the Upper Ruamāhanga valley area. The subcommittee ceased to exist after the Floodplain Management Plan (FMP) was adopted by Council on 25 June 2019. The FMP is now commencing the implementation phase, and further details will follow in the coming months.
‘A connected, resilient, prosperous and sustainable community, proud of its rivers, that is involved in managing flood risks in a manner that recognises local identity and protects, enhances or restores natural and cultural values’