Initiatives underway to reduce flood impact in Kaitaia in wake of Edgecumbe report

15 Dec 2017, 8:49 AM

Northland Regional Council – in combination with other organisations – is working through a range of measures to reduce the impact of potential flooding in Kaitaia, in response to recommendations contained in the report into the Edgecumbe flood event in April this year. 

Northland Regional Council (NRC) Chairman Bill Shepherd says most of Kaitaia is at risk because it is protected by stopbanks which could be ‘overtopped’ in a large flood event (meaning flood waters will flow over the stopbanks). 

“The Awanui catchment already has the greatest number of river and rainfall gauges in the regional council’s hydrology network,” says Councillor Shepherd. “There is an ongoing works programme which has seen expenditure of $350,000 per year since 2006, maintaining all channels through Kaitaia. As part of this programme, a significant project took place last year to lower one spillway. 

 “In addition, the Awanui River Working Party has been in existence for about 10 years as a partnership focusing on river management and bringing together the regional council and key stakeholders such as the Kaitaia community, iwi, the Far North District Council and other organisations such as the Department of Conservation. 

“However, a number of the recommendations from the Edgecumbe report are relevant, and we are putting these into place – and in some cases, bringing scheduled works forward – in areas with high vulnerability throughout the Northland region but most notably in Kaitaia.” 

Councillor Shepherd noted that one section of the Kaitaia stopbanks had overtopped during the storms of 2007, and had also come close to doing so in 2003. 

The area of Kaitaia between the Awanui and Tarawhataroa rivers was most at risk from flooding. Residents can view flood maps of the area online.  

 “In recognition of the importance of these measures, an option to upgrade the Awanui River Flood Scheme will be included in the regional council’s Long Term Plan 2018-2028 consultation document, which will be out for public consultation in March next year.” 

The Northland Civil Defence Emergency Management Group is assisting with a review of the Community Response Plan for Kaitaia, in consultation with the regional council’s River Management team. Alerting and evacuation procedures for Kaitaia in the event of a flood are also being reviewed in the context of the Edgecumbe report, and other planned work includes a public education programme and signage to ensure residents are aware of the flood risk. 

Northland DHB has also advised that it works with the managers of all residential care facilities that could be affected by flood (or tsunami).

Measures taken to date by the regional council include:

  • Improving the current hydrometric (rain and river gauge) network, including new and upgraded gauges and transmission of data via satellites, which are more reliable than cell or radio networks
  • Assessing the benefit of additional recording equipment and/or webcams near vulnerable stopbank areas
  • Reviewing warning thresholds
  • Stopbank condition surveys, peer review and geotechnical testing of existing Kaitaia stopbanks
  • Flood mapping
  • Upgrade of the Whangatane Spillway intake in 2015
  • Upgrade to Mathews Park and Choke stopbanks
  • LiDAR mapping to improve flood modelling
  • Hydraulic modelling of flood events
  • Grade control to improve stream bed stability on the Tarawhataroa and Awanui Rivers
  • Major Kaitaia Flood Scheme upgrade to give resilience and increase flood capacity.