Lower Ruamāhanga Valley

The Ruamāhanga river travels from the northern central Tararua Range through open country across the eastern side of the Wairarapa plains to Lake Wairarapa and Lake Ōnoke. The Lower Valley area covers from the Waiohine confluence to the Lake Ōnoke outlet. Other major tributaries include the Tauwherenīkau draining from the western Tararua Ranges include the Tauwherenīkau River draining from the western hills and the Huangarua, Tauanui and Turanganui Rivers flowing from the eastern hills. These rivers all flow through vast areas of farmland and are therefore susceptible to run-off particularly from dairy farms and disturbances from stock entering the river channel.

The Lower Wairarapa Valley system also includes Lake Ōnoke and Lake Wairarapa. Before the Lower Wairarapa Valley Scheme, a major flood could affect up to 20,000ha of land, with some areas being flooded eight times a year. Roads were blocked for days on end, communication lines damaged, and fences destroyed. Despite an efficient flood warning service which began in the 1950s, stock losses at times were severe.

The Lower Wairarapa Valley Development Scheme is one of New Zealand's largest and most ambitious land development and flood control schemes, benefiting a total land area of 41,000 hectares. Greater Wellington is responsible for the implementation and maintenance of the scheme.

The Ruamāhanga River was diverted from its direct course into Lake Wairarapa, across the Kumenga Peninsula and into the Lower Ruamāhanga. The barrage control gates largely prevent all normal flows of the Ruamāhanga from entering Lake Wairarapa.

The barrage has also enabled levels of Lake Ōnoke to be raised quickly to either overcome impending blockage of the outlet or to aid in the formation of a new opening. This also means that the lake can be kept at a low level, ready to accept any flows from the Oporua Floodway. Such flows are the result of the overflow of flood discharges from the Ruamāhanga River at various points further upstream. Flow size is dependent on the size of the flood event and cannot be controlled.

The ability to be able to maintain an efficient and ever-lasting outlet from Lake Ōnoke to the sea has been a key aspect of preventing flooding in the Lower Wairarapa Valley. The flood protection works were tested in the major floods of 2004 and they held up well despite the extreme conditions.  

The land-use patterns and environment of the Lower Wairarapa Valley are now well-established. Our aim is to allow for improvements in the quality and security of this environment. If you want more information about the scheme please contact Greater Wellington on 0800 496 734.

There is a long, history around the Wairarapa Moana and the flood management systems that are in place today.  Mana whenua recall the time when the lakes doubled, the sandspits closed over and the rains filled the Wairarapa plains.  For Māori this was referred to as the hinurangi. And inundation of water when eels migrate. For Farmers it meant flooding, so they opened the sandspit. Today this is knows as “The Battle of the Lakes” and you can learn more here:

This video was made by Ngāti Kahungunu ki Wairarapa, who have a deep connection to the Wairarapa and its wetlands. You can also visit their website, Wairarapa Glistening Water, to hear and learn more from tangata whenua within the area.

Flooding has always been a feature of the Lower Wairarapa. Almost from the first day of their settlement in the district around 1840, the new inhabitants experienced its severity. They considered the richness of the land compensated for the inconvenience of flooding.

As settlement became denser, a Wairarapa River Board was set up in 1886 in a communal attempt to reduce flooding. The main responsibility was the maintenance of a reasonable outlet through the shingle bar which separates Lake Ōnoke from the open sea of Palliser Bay.

With the limited means available, the lake had to reach a high level before an opening would be successful. This meant that large areas of valuable land in the Lower Wairarapa were unproductive in those early days.

Over the years, in addition to lake opening, the River Board carried out isolated stopbanking works and erosion protection schemes to generally improve conditions for landowners.

The Wairarapa Catchment Board - formed in the 1940s - was a body which had sufficient authority and statutory responsibility to plan and implement a major flood protection scheme for the Lower Wairarapa Valley.

However, a comprehensive flood control scheme for the whole district was not realised until the 1960s. Several major schemes were proposed previously but had never come to fruition. The last of these was proposed in 1948 with the aim of soldier rehabilitation farm creation, but this did not proceed.

Many of the ideas from earlier proposals were incorporated in the Lower Wairarapa Valley Development Scheme which was successfully launched in 1960.

Greater Wellington has more information about the scheme and the floodplain, the risk of flooding, and what has been done to minimise its impact. We are also responsible for how the scheme will be managed in the future.

The Lower Ruamāhanga Valley Floodplain Management Advisory Committee is made up of rate payers from the Lower Valley (one from each scheme area), a GW Councillor, a South Wairarapa District Councillor, a representative from Kahungunu ki Wairarapa and a representative from Rangitāne ō Wairarapa.

Members work to balance cost effective flood management solutions with environmental, cultural and recreational concerns along the Ruamāhanga River south of Greytown to Lake Ōnoke.

Scheme Areas Map

Find out which scheme area you live in.  

Enter your address in our web map.

Committee documents

Lower Ruamāhanga Valley Floodplain Management Advisory Committee (An advisory committee to the Environment Committee)

Purpose: 
Provide oversight of the development, implementation and review of the Lower Wairarapa Valley Development Scheme (LWVDS) and Floodplain Management Plans (FMPs) for the Lower Ruamāhanga Valley floodplains

Provide oversight of the… Read more here

date_range Published 09 Mar 2017

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Contact Us

Call 0800 496 734 or email info@gw.govt.nz.