Short-term fixes not enough for flood-prone
Nearly 200 flood-prone Christchurch houses may need to be tanked, raised or relocated to protect them, despite millions being spent on temporary solutions.
The Christchurch City Council set up the Mayoral Flood Taskforce earlier this year to look at short to medium-term solutions that would provide rapid relief for those affected by regular flooding since the earthquakes, such as the events of June 2013 and April 2014.
It looked at Dudley Creek/Flockton, Lower Avon, Heathcote Valley, Lower and Upper Heathcote, Southshore, Sumner and Lyttelton.
In its final report, released today, the taskforce outlines what work has already been done, what options are available, what else needs to looked at, costs and the social impact of the flooding.
Council land drainage operations manager and former task force leader Mike Gillooly said it was hard for those who had not experienced the devastation of floodwaters entering their home to understand what it was like.
''I have met many of you in school and church halls. I have sat around the kitchen table in your flooded homes and heard your stories, your frustration and your anger," he said.
"I have watched, helpess, as you evacuated your homes, carrying your children to the car in the middle of the night.''
Gillooly said the report offered viable solutions for some, and for others there was still more work to do.
The total cost for work in the Dudley/Flockton area is about $8.6 millions, with the majority of work already approved and either scheduled, in progress or completed. According to the report, this benefits about 96 properties.
The report, which will go before the full council tomorrow, asks for an additional $1.75m to complete the Tay St drain pump station, taking its total cost to $6.1m.
Council transport and greenspace manager John Mackie said the pump station benefited 65 per cent of owners and residents of the most damaged and vulnerable homes.
Other work includes removing and replacing the Guild St footbridge, negotiating the replacement of two private bridges that are causing issues in Dudley Creek, and improving channels and removing sediment from problem areas.
Outside of the Dudley/Flockton area, the taskforce recommends about $2.1m worth of immediate and minor works, of which about 65 per cent are either scheduled, in progress or completed.
The remainder need further work before approval.
The report considers temporary stopbanks in some locations along the Lower Heathcote at a cost of about $4.6m. However it recommends that Asset and Network Planning review this as it needs to be considered alongside the long-term options.
Gillooly said there would still be 12 level 1 and 186 level 2 houses in spite of these works.
''House tanking, raising and in some instances relocation are the only options for providing temporary flood defence to these houses. However these costs are unlikely to be borne by council.''
The total cost for this is about $6.1m, and is included in the report to show the costs of providing temporary flood defence to these vulnerable households.
Tanking involves applying a waterproof membrane to the exterior of a house, and relies on homeowners covering up vents and door openings with provided guards in the event of a flood.
The taskforce has not looked at funding sources, but instead focused on identifying options and estimating costs.
The report states a cost-share agreement with the Government may be possible.
RESIDENTS STILL IN THE DARK
Flockton residents' group spokeswoman Jo Byrne said no one knew whether their property was on the list of those needing individual defences.
"This is one of the issues. It's pretty frustrating to residents because they need this information to make decisions."
Byrne did not know what would happen to her own property on Carrick St, which dropped 400mm during the earthquakes.
"What we'd really like is to have our land lifted back to where it was. We want to be safe and dry."
It was almost six months since the March 5 storm that caused widespread flooding across Christchurch, and residents wanted to know if their homes were going to be safe in the future, she said.
"We can't sit around waiting for more consultation."
BY THE NUMBERS
- 77 homes had flooded above floor levels twice or more (level 1)
- 427 homes had suffered flooding below floor level two or more times (level 2)
- 948 homes had access compromised by flooding three or more times (level 3)
PROPOSED WORK AND WORK CURRENTLY UNDER WAY INCLUDES:
- Major waterway channel widening and deepening
- Temporary pumping solution in Flockton
- Reinstatement of stopbanks in some areas
- Installation of backflow prevention mechanisms on drains
- The repair of flap gates in the Avon and Heathcote rivers
- Removal of sediment, vegetation and debris from waterways
- Bridge and culvert removals
- Raising the height of the sides of timbered drains
- Installation of the Tay St drain pump station