Wet weekend unusual for summer

 

This last weekend’s rain was unusual according to Hawke’s Bay Regional Council.  Council records show that heavy rainfall in summer is more likely to happen in December or February, but is less common in January.

The Council says that even though the rain has eased off, more slips can be expected across the wetter areas of the region during the next few days.  

The region’s flood protection worked as it should, but the Regional Council warns that there may be problems if there is more heavy rain during the next week.

“The ground is already saturated and rivers are full, so if there is another band of heavy rain in the next week, we could expect rivers to rise very quickly and to have problems with slips, tree fall and flooding,” said Mike Adye, Group Manager Asset Management at Hawke’s Bay Regional Council.

“We will be keeping a careful watch on the situation.”

On Sunday [31 Jan] a heavy rain warning was received soon after 9 am which predicted 120 to 180 mm of rain, but the Council had already been receiving rain and water level alarms from 8am via their automated telemetry monitoring network.

Rainfall was widespread and steady over the region during the 48 hour weekend period, with higher rainfall of over 200mm recorded in the northern region.  Over the last week in excess of 400mm of rain was recorded on the Ruahine Ranges.  

Rivers in the Wairoa district rose on Sunday to levels seen once every 5 years on average.   The front moved south over the day, and alarms at recorders at a number of sites were triggered at Hawke’s Bay Regional Council as rainfall and river levels rose, with some levels seen once every 20 years on average.  

The Council today received reports of a lot of woody debris coming down through the Waikari River catchment and expects that intense rainfall has caused an unknown number of slips and tree falls within the Mohaka forest and pastoral areas.  

The upper Ngaruroro River at Kuripapango exceeded its flood levels seen on average every 50 years.  However by the time the water had travelled downstream to Whanawhana in the early hours of Monday morning, it had dissipated to only an annual flood level.

In Central Hawke’s Bay, the Makaroro River also reached a 50 year flood level at the Burnt Bridge site but the levels were at only 1 to 5 year levels as the water moved down the Waipawa and Tukituki Rivers.

“People would have seen many riverside (berm) areas going under water and water reaching the toe of some of the stopbanks, but the stopbanks worked as they are designed to protect land, homes and industry,” said Mr Adye.

Aquifers and soil moisture levels have been temporarily recharged by the heavy rain, which will alleviate the usual summer time concerns for the agriculture sector.