Flood mitigation options to be shared with community

Some communities affected by flooding since the earthquakes will learn more about two fast-tracked options to address issues in Flockton Street and surrounding areas.

Christchurch City Council today received a report outlining two options to restore public drainage systems around Dudley Creek, which affects the Flockton area, to provide a similar level of protection to that before the earthquakes. The two options being considered are:
* a culvert upgrade and channel widening programme
* a pump station and bypass system.

The report provides the context for the proposals, including background about the Council's work to address flooding issues across the city since the earthquakes, and how the Dudley Creek options fit into that wider programme of work.

Christchurch Mayor Lianne Dalziel says the Flockton community has been hit hard by flooding problems since the earthquakes and it is a Council priority to address the issue.

"The Council has been working with other agencies to understand all the post-earthquake flooding issues facing the city and to design solutions. As the Flockton area has experienced three significant flood events since the earthquakes, work in this area had already been prioritised by staff.

Staff were asked to fast-track the Dudley Creek options report as a result of the latest rain event in March.

The Mayor said that this has not stopped the work on the challenges the city faces with increased vulnerability to flooding affecting a number of areas.

"Residents in this particular area have been badly affected since the earthquakes and we need to find workable solutions."

The Council will now present the options to the community to explain in more detail what is being considered and what it means for residents.

"The options being considered will require significant construction works in the area over the next two years, so we want to take the time to discuss the plans with the community before we make a final decision," Mayor Dalziel says.

"It is important we act as quickly as possible to address the issues, but it is equally vital that the community understands what is being proposed and is involved in the process. We will be contacting residents directly to invite them to community drop-in sessions next week so they can find out more about what's involved."

The Council report recognises that the Dudley Creek options are a significant part of a wider piece of work being carried out to address post-earthquake flooding in the city. This work recognises that Christchurch has always been a low-lying city and prone to flooding and aims to return land drainage systems to provide, where possible, pre-earthquake levels of flood protection.

"I think it is important for people to realise that we cannot remove the risk of flooding entirely, but if we can find solutions that protect against the kind of event we had in March, and then we will have addressed one of the most significant land-use challenges that were exacerbated by the earthquakes."

The wider piece of work underway involves a number of recovery agencies and covers physical options, the level of flood protection to be achieved, funding of works, insurance implications, Council's review of the District Plan, the requirements of the Building Act and the personal circumstances of property owners.

A technical joint working party has been established between the Council and CERA to ensure that the wider response across all agencies of Government is well-connected.

Background on the Dudley Creek options

Option 1 - Major Upgrade of Watercourse
This option would improve flood protection by increasing drainage capacity through increasing the width and depth of watercourses, including all of Dudley Creek downstream of the Aylesford culvert to the Avon River, and short sections of Shirley Stream, Bings Drain and St Albans Creek. It also includes the replacement of culverts at 12 road crossings, two public footbridges and 29 private vehicle bridges.

Construction would require major works and traffic management. It would impact 115 properties to some degree. This option would benefit 550 properties and cost $50 million.

Option 2 - Pump Station, Flow Diversion and Lesser Upgrade of Watercourse
This option would improve flood protection by diverting flood waters from key areas by building a pump station within the Flockton area and a piped diversion to Dudley Creek at the intersection of North Avon Road and Banks Avenue. It would also increase the width and depth of watercourses, including all of Dudley Creek downstream of the Aylesford culvert to Warden Street and the section near Banks Avenue, Dudley Creek between Warden Street and Stapletons Road crossing and short sections of Shirley Stream, Bings Drain and St Albans Creek. It also includes culvert replacement at six road crossings and two public footbridges and 21 private vehicle bridges.

Construction would require major works and traffic management. It would impact 70 properties to some degree. This option would benefit 490 properties and cost $53 million.

More information is available online at www.ccc.govt.nz/DudleyCreekRemediation

Community Information Sessions

Date: Wednesday 2 April 2014 and Thursday 3 April 2014,
Time: 6pm to 8pm
Venue: Shirley Boys High School, Main Assembly Hall (entry via Averill Street), North Parade, Richmond.

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