What's happening with the Halswell River?

Lateral spreading. Water levels are about 0.5 m higher than normal at the Halswell River off Old Tai Tapu Rd, near Rossendale Winery.

The 4 September 2010 earthquake caused extensive damage to the Halswell River network. The risk of flooding has increased for residents living near the Halswell River.

Environment Canterbury has work underway to fix some of these problems, but large-scale repairs are needed and these will cost a lot of money.

Earthquake damage

Woods Drain full of sand being cleared near Tai Tapu golf course.

The earthquake caused extensive damage in the catchment. The risk of flooding in the district has increased because:

• sediment has accumulated and reduced channel capacity
• collapsing banks have reduced the width of the drainage channels
• land has subsided
• and because of raised water levels it is difficult for groundwater to drain and is more prone to flooding.

Environment Canterbury has completed an initial report of changes to the Halswell Catchment drainage system. The immediate problem includes blocked drains and raised river beds, which in turn limits the ability of the system to control groundwater.

Lowering water levels in the Halswell River and removal of silt from substantially compromised drains was a top priority and work started in September to remedy this. In parallel, engineers have carried out a more detailed inspection of the drainage system and mapped the damage.

Background to the Halswell River Rating District

The catchment of the Halswell River lies to the south of Christchurch. It extends from Hornby in the north to the river’s outlet at Lake Ellesmere in the south. Small centres of population on the plains include Prebbleton, Tai Tapu and part of Halswell. The total catchment area is 18,800 hectares.

The eastern part of the catchment is moderately steep hill country used largely for extensive pastoral farming. The western and middle portions of the catchment are generally flat, arable land used for intensive agriculture and housing. In its natural state this land was swamp, with the Halswell River providing the only drainage outfall.

Historically, rain has caused the Halswell River to flood, and water ponds on the flat land disrupting drainage, housing and restricting farm operations.

The catchment is served by an extensive drainage network. The flat areas have very little fall, so in the past the drainage network has been carefully and rigorously maintained.

The Halswell Drainage District was established in 1893 by the Selwyn County Council under the Land Drainage Act 1893. The Land Drainage Act 1904 and the Ellesmere Land Drainage Act 1905 saw the establishment of the Ellesmere Land Drainage Board, which took over responsibilities from Selwyn County. The Ellesmere Land Drainage Board was then succeeded by the North Canterbury Catchment Board in 1948 and by the Canterbury Regional Council (now Environment Canterbury) in 1989.


Collapsed bank at Halswell River upstream of SH 75 near Halswell, between Wroots Rd and Saby’s Rd.

The way forward

The immediate response for restoring a degree of groundwater level control will finish once sediment has been removed, with an estimated cost of $570,000. This has been charged to the rating district, and has been partially offset by a cash reserve. The balance of the costs will show as a deficit in this account. No further work will take place until funding decisions are made.

Environment Canterbury is putting a case to the Ministry of Civil Defence and Emergency Management, seeking assistance with the recovery costs that the Halswell Rating District faces.

At this stage we do not know exactly what proportion of the recovery costs will be funded by the Ministry of Civil Defence and Emergency Management. A figure of 30 % has been used to determine the effect on rating. It is proposed that a special Halswell earthquake recovery rate will be levied over a 10 year period for repaying the balance of the restoration costs.

Environment Canterbury Commissioners will be informed by the advice of the community and the Halswell rating district liaison committee when deciding how to pay the restoration costs through the Council’s 2011/12 planning process.

Comments and feedback on the two possible two repayment options closed on the 24th December 2010. Please contact our customer services team if you have a further enquiry or question.

To discuss the options please contact a district liaison committee member or view the Halswell Drainage District Earthquake Reinstatement Plan report (pdf 3.11 MB).

District liaison committee members:

• Craig Scott ph 329 6842
• Tony Nixon ph 329 6455
• Brent Rawstron ph 322 9293
• Jim Macartney ph 329 6734
• Alister Fiecken ph 329 6798
• Simon Manson ph 329 7807

Restoring the district’s drainage

Much of the land that needs to be disturbed to widen the river and/or undertake bank stability work is either riverbed or road reserve. However, in some places, particularly the narrower upper reaches of the river, where there is no road reserve, landowner co-operation will be essential.

The rating district today

The drainage system now consists of a series of main drains discharging to the Halswell River. The Halswell River runs from Halswell Junction Road, generally around the foot of the hills to Tai Tapu, discharging to Lake Ellesmere via the Old Course and the Halswell Canal. The system of main drains and the river serves as the outlet for farm drains and roadside drains constructed and maintained by property owners.

The objectives of the Halswell Drainage District are:

1. To maintain the drainage system to provide for efficient and economic drainage of the Halswell Drainage District.
2. To control lateral and bed erosion of drains.
3. To maintain the cross-section shape and grade of the drains.

Most maintenance is funded by rates, the level of rating being determined each year by Environment Canterbury’s Annual Plan process. Your targeted rate is itemised on your Selwyn District Council and Christchurch City Council rates. Funding comprises:

• 80 % Targeted rate levied within the classified area of the Halswell Drainage Rating District.
• 15 % Works and Services rate, levied across Christchurch City and Selwyn District Council.
• 5 % General rate.

This is supplemented by income that is generated annually from leasing of land in the Ahuriri Lagoon, a frequently flooded area.