Whakatāne Mayor Victor Luca says he considers building more homes within Matatā now would be a mistake.

Matatā is one of the areas named in the draft Eastern Bay Spatial Plan as a key growth area for housing with infill housing of up to 700 homes and the potential for development of up to 800 homes eastward of Pollen Street over the next 30 years.

At an infrastructure and planning committee meeting yesterday, council learned that since August, Whakatāne District Council has spent more than $300,000 clearing sediment and debris from Matatā, washed down from stream catchments due to localised “rain bombs”.

Most of the cost was incurred between February and May due to several heavy rain events in the hills above the town during that period.

After the 2005 debris flow, the council placed sediment and debris catchpits in Matatā, both at the Awatarariki Stream on the western side of the town and Waitepuru Stream on the north-eastern side of the town.

A $70,000 annual maintenance budget is supposed to cover the cost of keeping these catchpits clear, so the town and lagoon do not suffer debris flooding events. Despite this, earlier this year heavy rainfall localised in the hills above Matatā saw sediment and debris overwhelm Moore’s Bridge, which crosses the Awatarariki Stream, blocking State Highway 2 and entering properties on Pioneer Place.

Although some of the cost overrun for removal of debris could be covered by an emergency stormwater fund, $112,000 of unbudgeted spending needed to be approved, which would likely come from an internal loan. This amount also included repair of a blown-out stormwater pipe in Murupara.

Three waters manager Jim Finlay had some suggestions of how this sediment and debris coming down the rivers could be mediated with rock weirs slowing the flow of the water, at an estimated cost to the council of $140,000.

"It’s terrible that we’re just sitting there waiting for this to happen and you have to clean up each time and if you don’t you are possibly going to have flooding down the highway and through the town from both of those streams.”

He likened it to “someone having a party in your house every week and you’ve got to go and clean up the mess”.

Dr Luca said it would be a mistake to densify Matatā with what was going on there at the moment.

“Climate change is the elephant in the room, and we seem to have consistently underestimated the effects. There’s a micro-climate [in the Matatā catchment]. It’s not totally predictable, but it looks like things are going to keep getting worse. These rain bombs that come - this is the second in 20 years, but they don’t have to be linear, there could be another one in a year or two.

“This has to be fixed and the people living there have to be given some comfort.”

Councillor Gavin Dennis recently gave a presentation to the Bay of Plenty Regional Land Transport Committee about an incident earlier this year in which Moores Bridge, which crosses the Awatarariki Stream, was overwhelmed with debris, closing State Highway 2 and flooding some properties with waist high sediment.

He asked that the bridge be improved and that New Zealand Transport Agency and New Zealand Rail increase their maintenance on their State Highway 2 and railway bridges.

Mr Finlay said yesterday that New Zealand Rail had since cleared out their culverts on the Awatarariki Stream and had further work planned for clearing culverts on the Waitepuru Stream.