Blood, sweat, and detainment bunds

The Roe family farm, situated high in the hills of Mamaku ranges in Rotorua, is a testament to the “can do” mentality. Four generations have cleared, farmed and restored the land to ensure future generations can operate sustainably and improve water quality within the region. The Roes manage a total of 324ha of land which today is mainly used for dairy farming.

John Roe’s great grandfather Alfred William Roe Senior purchased the land in 1898 to mill timber. Once the forestry industry dried up, they then began farming. In 1927 they walked off the land when their stock were struck down with bush sickness (cobalt deficiency), however the Roes came back 18 years later in 1945 to begin farming again. At that time the blackberries had taken over and in some places were 3 meters tall.  John’s grandfather Alfred William Roe Junior, father Arthur Roe and uncle Noel Roe had to start by clearing the blackberries which was a mammoth task, so John fully understands why it’s crucial to continuously control this pest plant.

John Roe and his wife Wendy are dedicated to improving water quality from their property and have been working closely with Toi Moana on a series of Environmental Programme (EP) initiatives. One key EP is to minimise their impact on the land and restore the quality of the water coming off their farm which ultimately ends up in Lake Rotorua.

“Like any good farming practice, long-term and ongoing commitment are key,” says John.

Baylee Jackson , Toi Moana Senior Projects Manager explains that there was an independent review following the Ngongotahā floods in 2018 that looked at causes of the flood and explored mitigations to improve flood resilience in the region. Detainment Bunds in the upper Rotorua catchment were one of the recommended actions.

The construction of the Roe’s four bunds began in 2020 and was completed by early 2021. These detainment bunds were 100% funded through the Covid recovery funding. This was allocated to implement the recommendations of the Ngongotahā Flood Review from money received for the Bay of Plenty Flood Resilience Project. Tonkin + Taylor were the engineers of the bunds, and they were constructed by Josephs Earthmoving.

The engineered earth ‘detainment bunds’, which essentially look like low grassy berms and are designed to temporarily capture waterflow during storm events. The water then seeps through the earth or through the small pipe in the bund, and into the remnant native bush below. The idea is that a large portion of the sediment and nutrients get filtered out as it settles, and therefore don’t transfer down into the Lake Rotorua catchment.

“We’re getting more and more heavy rain events, so these bunds are hugely beneficial to stop both sediment and nutrients travelling further downstream,” says Baylee.

These bunds can reduce phosphorus by 47% to 68%*. There is also further research being done to confirm how the bunds also reduce e-coli and Nitrogen, so these bunds are hugely important for restoring the Rotorua catchment from nutrients and sediment.

“Having the science from a landowners perspective shows us how important the bunds are,” says John.

Toi Moana also supports the Roes with planting, pest control, advice, support and guidance around detainment bunds, as well as supporting them through our Environmental Programmes to fence, carry out pest plant control and to plant native trees on less productive areas on the farm such as steep gulleys.

The Roes, with support from Toi Moana Bay of Plenty Regional Council , QEII National Trust , Ministry for Primary Industries (MPI) , and Ministry for the Environment | Manatū mō te Taiao , have now excluded stock from around 28ha of existing native bush and retired and planted an additional 25ha which will collectively support the goal of the Lake Rotorua Nutrient Rules and add to biodiversity within the catchment.  By retiring land, we are not only preserving natural habitats but also improving soil health and water quality.

Scott Kusabs , Toi Moana Land Management Team Leader, says sustainable farming requires collaboration, innovation, and a commitment to long-term environmental health from both landowners and local Council.

“By utilising a variety of tools and strategies, we can achieve significant improvements in water quality, soil health, and biodiversity, ensuring a sustainable future for farming communities.

You can find out more about the Rotorua Te Arawa Lakes Programme to restore the Rotorua catchment here:

*Source from ‘Detainment Bund PS120. A guide for on-farm, pasture based, storm water run-off treatment. 200518 V13’.