Flooding wrecks riverside work
Temporary river channel works designed to protect the Ashhurst Domain from further erosion by the Manawatu River are likely to have been damaged or totally destroyed by this week’s flooding.
Horizons Regional Council and the Palmerston North City Council invested $100,000 this winter to build a shingle bank diverting the river flow away from the ravaged river bank.
But the work was no match for floodwaters on Thursday night as the Manawatu River rose to a height of more than 6.5 metres at Teachers College yesterday morning.
City council general manager for City Networks Ray Swadel said he expected the work would have been lost.
‘‘The coffer dam will have been inundated, but we will have to wait for the water to recede to see the damage.
‘‘It was an attempt to control it, but it was always going to be vulnerable to this level of high flood.’’
The river was running bank to bank at the State Highway 3 bridge below the domain yesterday.
Horizons river management group manager Ramon Strong said most of the region’s flood protection assets had weathered the storm well, but there was concern about the temporary works at Ashhurst.
He said river levels were still too high to fully evaluate what might be going on below the surface.
‘‘With snow melt feeding river flows, it may be a while before the river recedes enough.
‘‘River confluences are inherently complex things, so we aren’t really going to know what we are dealing with until both the Manawatu River and the Pohangina River recede.’’
Strong said he did not think the councils would be back to square one with managing the erosion problems.
‘‘However, more work will likely be required.’’
He said the city council would have to make the call about what more to do. It owned the domain on a waterway that fell between river management schemes.
The councils estimate a longterm solution, such as rock work on the left bank, would cost more than $1 million.
Ashhurst resident Harvey Jones saw the river was scouring into the domain again.
A century-old pine tree, estimated at 30-metres tall and weighing 50 tonnes, had finally succumbed to the river after being left teetering on the edge after flooding caused by the tail-end of Cyclones Debbie and Cook in April.
Jones said it would be a matter of wait and see to find out whether the river would drop back into its new channel away from the banks, or whether there was enough of the shingle bank left for it to settle on the other side.