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Managing erosion on my farm

Soil erosion is a critical issue for our region’s farm land. It represents a loss of current and future potential productivity and affects water quality in our streams and rivers. Financial support and trees are available for farmers from the regional council to help manage erosion-prone land.

Understanding erosion and its effects

Erosion remains a major challenge for Hawke’s Bay, particularly across its steep hill country. About 252,000 hectares are considered high risk. Heavy rainfall and fragile geology mean soil can move quickly, washing into rivers and eventually out to sea.

Each year, an estimated 3.27 million tonnes of sediment enter the region’s waterways, the equivalent of 136,000 truck and trailer loads, or 1,090 Olympic sized swimming pools filled with sediment.

This level of erosion has significant consequences. For farmers, it can represent both a loss of current and future potential productivity on the farm. Sedimentation also impacts water quality within the region and the biodiversity (both aquatic and terrestrial) that depends upon it.

What can I do on my farm?

  • Identify areas of land that are prone to erosion and consider planting trees within paddocks. Plant trees in paddocks. Pole planting can reduce erosion by up to 80 percent, while also providing additional benefits such as diversifying farm income through timber products, stock feed, or honey production.
  • For steeper or retired marginal land, fencing, and planting these areas in permanent vegetation can further reduce risk. Established, closed-canopy forests can be up to 16 times more effective than pasture at preventing landslides.
  • Where erosion is more advanced and concentrated in gullies, additional measures like a series of strategically placed debris dams may be needed.
  • Complementary measures, such as riparian planting along waterways, can also help stabilise banks and reduce erosion.

Effective ways to manage erosion

Willow and poplar planting

A simple erosion control method where tree poles are planted into the ground to grow into trees that stabilise soil and help slow runoff.

The Regional Council has a selection of poplar and willow poles for sale each year. These poles have been bred especially for farm planting.

Find out how to order willow and poplars here

Managing gully erosion with debris dam construction

In some cases, gully erosion can be managed by implementing a series of strategically placed dams. The Regional Council has expertise in constructing debris dams and can advise if these are suitable erosion controls for your farm.

Debris dams are small control structures that are built in the stream beds of actively eroding gullies. They stabilise the gully floor and allowing tree planting to minimise further erosion on the gully sides. While vegetation is generally the main long-term tool for gully control, trees can be difficult to establish if water channels continually undermine the toes of the hill slopes.

Where debris dams are used

Debris dams are largely confined to the control of v-shaped gullies. They are normally built in series over time, with the base of the upstream debris dam level with the top of the debris dam below. Locating a suitable site to commence debris dam construction is an important part of ensuring their success. It is important that the site is able to give sufficient support to the sides of the dam.

An effective debris dam system will:

  • manage grade control, by eliminating bed level fluctuations
  • reduce water velocity by lowering the slope angle and increasing channel width
  • raise and stabilise bed levels, thereby supporting the base of -adjacent gully slopes
  • centralise water flow in the channel
  • trap and hold sediment. This not only gives associated tree planting a better growing medium, but also helps reduce how much sediment is deposited downstream.

Talk to us about erosion

Call one of our staff for advice and assistance.

Northern Office - Wairoa
46 Freyberg Street,  Wairoa 4108
+64 6 835 9200

Central Office – Napier
159 Dalton Street, Napier 4110
+64 6 835 9200

Southern Office – Waipawa
26 Ruataniwha Street, Waipawa 4210
+64 6 835 9200

Debris dam case study – Onenui Station

The Station is on Te Māhia and has areas of highly erodible coastal land with deep v-shaped gullies prone to sediment loss whenever there was rain.

The Council worked with other agencies and the station owners to install a series of debris dams in June 2023 at one site on the station. A video of the installation is below.

It was pleasing to see that within weeks the debris was at such a level that planting of Poplar and Willow poles was possible to further stabilise this area.

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info@hbrc.govt.nz

+64 6 835 9200


159 Dalton Street. Napier 4110

Private Bag 6006, Napier 4142


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