Kāpiti Coast District Council is seeking feedback on its draft flood maps and models to make sure the community have input prior to them being finalised.

Infrastructure and Assets Management Group Manager Sean Mallon says Council uses flood modelling to map how high rainfall is likely to affect the district’s urban drainage and stormwater networks and streams and the extent of flooding should these systems become overwhelmed.

“Since our previous flood maps were published in 2011, modelling technology and data have come a long way,” says Mr Mallon.

“We’re updating our maps so they’re more detailed, cover areas not previously modelled, and account for infrastructure improvements such as stormwater upgrades and the Kāpiti Expressway and Transmission Gully.

“Our updated maps model potential impacts from a major rainfall event that has a one percent chance of occurring in any year (often referred to as a 1-in-100-year storm). They show a 100-year rainfall event under current climate conditions, and climate change +1.8oC and +3.7oC scenarios.

“Together these scenarios provide us with an understanding of potential flood risks, both in the present and having regard to potential climate change.

“While the Kāpiti Coast hasn’t experienced a 1-in-100-year event yet it is prone to flooding thanks to our coastal plains, rivers and peatlands. The updated flood models will help us plan and prioritise stormwater upgrades, make more informed planning and development decisions, assist with emergency management, and provide residents with local flood risk insights.”

The improved accuracy of the maps mean some people previously identified as being at risk of flooding or minor ponding would no longer be, while others who had not previously been affected may now find their properties included in the maps.

Mr Mallon says a letter has been sent directly to those newly identified property owners.

“We’re engaging with our community on the draft maps to check they reflect what our residents know about their property and local areas of interest and encourage them to get back to us if they think there’s something we’ve missed.

“This could be as-yet unmapped drainage features in their neighbourhood, historic flooding they’ve witnessed or know about, or unique property characteristics our modelling might not have accounted for.

“Where new evidence shows it’s needed, we’ll adjust the flood models behind the maps before we finalise them.”

Council will be holding a webinar this evening at 5.30pm and drop-in sessions around the district from Saturday 10 May.

Go to haveyoursay.kapiticoast.govt.nz/FloodMaps to register for the webinar, find the drop-in dates, learn more about flood maps and models, review the flood map portal and to submit feedback.

Feedback closes at midnight on Sunday 8 June.

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