Cyclones put focus on flood protection
Rain, rain, and more rain.
Easter this year saw some concentrated heavy rain fall on the rural land of Piako.
The catchment was already saturated from previous downfalls and we watched as tropical Cyclone Cook headed towards us.
The farmers were certainly concerned and the unanswered questions were, will we just get the rain or will we also have to deal with gale force winds?
Will the cyclone actually hit us and what sort of damage can we expect?
Waikato Regional Council manages the two main flood protection schemes in the area, the Waihou scheme and the Piako scheme.
The Waihou is mainly a river control while the Piako provides land protection especially to the very flat lying areas of the Hauraki plains.
Both systems responded as designed but the majority of flooding occurred to farms in the Piako area.
The Piako River Scheme was constructed in the 1950/60s with funding from local landowners and the government of the day.
It includes some 166 kms of stop banks, floodgates, and pumps, some owned by the scheme while others are privately owned by the farmers.
Many of the assets are old and the whole scheme is up for much needed improvement.
When you drive to Ngatea you can see the vast area of land that make up the plains.
The gradient is around 1:5000 which does not encourage natural flow. The Waitoa and the Piako rivers converge at Patetonga and eventually discharge into the Hauraki Gulf.
This in itself is not simple as each incoming tide forces sea water back up the rivers slowing the normal discharge.
When the rain came it was extremely heavy and concentrated. In many areas it over topped the stop banks and flooded the lower farming land.
This was to be expected but many farmers noted that something was different this time.
Areas that hadn’t flooded in
‘‘The Paeroa-Tahuna road totally disappeared under one large lake over the whole area with other roads stopped by flooding.’’
previous events were now flooding and water in the usual ponding areas came up faster and higher.
The Paeroa-Tahuna road totally disappeared under one large lake over the whole area with other roads stopped by flooding.
Water that would normally flow through the large Kopuatai Peat Dome in the area was no longer flowing freely.
Some suggested that the recent Kaikoura earthquake had caused the land to rise over the fault line running through the area.
Others believed that the farming land surrounding the peat dome had shrunk to a greater level than expected.
Department of Conservation manages the peat dome and some farmers believe that DOC has made recent change to their management of the dome by installing numerous weirs to hold water in all year round.
I guess a debrief now the rain has gone will answer some of the questions as to what was different this time.
Farmers are well known for complaining about the weather, but this time many of our local farmers face serious threats to the short term viability of their businesses. We will all feel the financial impact.
-Hugh Vercoe is a Waihou councillor for the Waikato Regional Council.
Roads surrounding Patetonga flooded after cyclones Debbie and Cook passed over the region.