Environment Waikato has been granted resource consents to build a stopbank along the Waikato River near Mercer West to protect an additional 355 hectares of floodplain and wetland.
The Council’s application, heard before commissioners, attracted 15 submissions to Environment Waikato and 10 to Franklin District Council from neighbours, Transit New Zealand, Swann Road Drainage District, Historic Places Trust, Central Eel Enhancement Co Ltd, Department of Conservation, River Watch and others.
The Regional Council intends to construct a 6.8 kilometre stopbank on the western bank of the river, a 2.25 kilometre stopbank on the Morrison Rd drain, a number of stormwater discharges, a short temporary diversion of the Morrison Rd drain and one floodgate and a temporary culvert on the drain.
The intention is to extend the Lower Waikato Flood Control Scheme and provide protection from a one in ten year flood to more land. Submitters were concerned about the stopbank construction, floodgate effects, loss of wetland and floodplain, flooding and riverbank erosion and lessening of the effects. The stopbanks are to be built using clay fill excavated by Transit during re-alignment of State Highway One.
The Committee said no adverse effects were likely from the construction works and the design proposed was sufficiently robust to ensure the banks will be suitable. A “fish friendly” floodgate was an important feature of the proposal and the Committee encouraged the applicant to continue replacing or modifying all floodgates in the Region to allow the optimum passage of fish.
One of the main concerns of submitters was the potential to increase flooding on “unprotected” properties and increase erosion on the banks. The only area adversely affected would be a stretch of SH1 south of Meremere, which Transit New Zealand had made arrangements to buy and was unconcerned about increased flooding potential.
A training wall was to be built to protect a bank of the river where active erosion was already taking place, which would address submitters’ concerns. No further erosion was predicted under design flood conditions, and the applicant’s undertaking erosion control works at selected locations outside of the consent process was a responsible action.
Excluding cattle from riparian areas outside the stopbanks and planting with appropriate, flood tolerant plants would also significantly reduce erosion potential.
The primary effect would be the loss of periodic flooding over the area which would also result in the loss of a large area of marginal wetland – 50-60 hectares – and some pasture dominated floodplain. This would result in loss of feeding opportunities for eels and other native fish, loss of habitat for wetland fauna and overall loss of wetland in the Region.
The applicant had gone to some lengths to provide certainty about the outcomes of efforts to lessen the effects while leaving necessary flexibility about how this was to be done. Provided the outcomes and minimum timeframes could be defined, it was appropriate that the mitigation package be left to be developed as part of a management plan for the area, the Committee said.
The applicant had made a commitment to ongoing mitigation and consultation through a management plan for the Opuatia wetland, and the proposals will be likely to provide a greater benefit than the minimum required by the proposed consent conditions, and would also have positive effects on the water levels and vegetation in the area.