Christchurch City Council has engaged GSL to build the earthen dam in Cashmere Valley to protect more homes from the risk of flooding.
“The contractor is about to begin work and the goal is to have the dam completed within 12 months,” said Helen Beaumont, three waters council chief.
“With the dam in place, we have an additional 213,000 cubic meters of flood storage capacity in the upper valley, meaning we are protecting homes along the lower and middle Ōpāwaho Heathcote that are at risk from above-ground flooding in a rainfall event.” of one in 50 years.”
The dam is the last major part of the Cashmere Worsleys Flood Storage Project, which the council has been working on for the past five years.
The first phase of the project involved installing locks in the lower part of Cashmere Valley, close to Worsleys Rd.
During a heavy rain shower, the sluices can be closed, allowing the lower valley to function as a rainwater storage basin.
The lower valley can hold up to 500,000 cubic meters of water that would otherwise flow into the Ōpāwaho Heathcote River.
The valley is also formed to allow as much sediment to settle as possible before the water leaves the valley.
This will improve water quality in Cashmere Stream and the Ōpāwaho Heathcote River.
Paths have been constructed in the upper part of the valley to facilitate public access, while extensive wetland and forest planting has been carried out throughout the valley.
The final stage of planting will take place once work on the dam is complete. Simultaneously with the construction of the dam, additional paths will also be built in the lower valley.
“The dam structure is the last part of this floodplain management plan,” Beaumont says.
“It will provide greater resilience to flooding associated with unpredictable and increased rainfall due to climate change and back-to-back wet weather events.”