Environment Waikato is training the Waipa River to control major erosion problems.
The Regional Council is carrying out a major river works project that is gradually changing the Waipa from a braided river to a single meandering channel. The works involve artificially “training” the main channel using erosion control works and plantings.
The river works are designed to manage the downstream effects of a 1991 landslide at the headwaters of the Tunawaea Stream which caused a dam across the stream. The dam failed in 1992, drowning the Waipa River channel with debris that has been gradually moving downstream.
Sediment and gravel from the landslide still loads into the Waipa River, causing flooding and erosion, and has changed the river into a braided system. The Council is concentrating on a 30 km stretch of the river, from Toa’s Bridge near Otewa to just downstream of the Waipa’s confluence with the Tunawaea Stream. The Department of Conservation, Fish and Game and local iwi are supporting the project and an Iwi Management Plan has been developed to recognise the river’s cultural and spiritual values.
A total of 21 km of fencing has been completed over the past three years and 8000 willows and 5000 flaxes planted, with 1500 metres of channel reconstructed. The plantings have ‘locked up’ gravel, reducing sediment flowing into the river and improving water quality. Local fish returned very quickly, and fish habitats have been restored.
A comprehensive animal control programme has also been carried out with local landowners and DOC to control goats in the upper catchment. More than 2000 goats have been culled, allowing the willows and natives to grow.