While this flooding is generally caused by heavy rain, the extent and depth of the flooding can be exacerbated by high groundwater levels and resurgence flow.

Following flooding in June 2014, budget was allocated in later years for the Mandeville Resurgence Channel Upgrade and Diversion Project.

We are planning on implementing upgrades to improve the management of stormwater and resurgence flow through Mandeville.

Investigation work identified that there are options to improve the drainage in this area.

Three potential options for Stage 1 and one potential option for Stage 2 have been identified.

Stage 1 will focus on upgrades to the existing channel and we’re asking the community which option of the following they prefer:

Option A: Upgrade existing main drainage channel through Redfern Lane, over Tram Road, through Millfield subdivision into Bradleys Road drain.

Option B: Install a culvert to convey stormwater flow to an open drain on the south side of Tram Road, then utilise the stock race to convey flow.

Option C: Install new 900mm diameter pipe from the Tram Road culvert outlet to Bradleys Road drain.

In Stage 2 we will look to construct a new open drain to divert stormwater along No. 10 Road south to the Old Bed Eyre River. The Old Bed Eyre River discharges into the Silverstream which flows into the Kaiapoi River.

These upgrades will increase the capacity of the drainage systems from approx. 0.5 m3/s to 2.0 m3/s (about four times the existing capacity depending on the recommended option).

While this is a significant improvement, surface flooding will still occur in larger rain events.

We’re hosting two drop-in sessions so that you can view the potential options, talk to the project team, and let us know what you think.

Drop-in sessions

Monday 11 September | 3pm – 7pm | Mandeville Sports Club

Thursday 14 September | 3.30pm – 7pm | Ruataniwha Kaiapoi Civic Centre - Kāikanui (Meeting Room 1)

If you are unable to attend a drop-in session, you can still provide feedback online at waimakariri.govt.nz/letstalk. Feedback received will inform the selection of potential options moving forward. Have your say before 5pm, 29 September 2023.