New Zealand Records Largest Flood Flow In Almost Century
Umer Jamshaid 2 months ago Thu 29th July 2021 | 12:51 PM
Flood flows on South Island's Buller River this month were the largest of any river in New Zealand in almost 100 years, the National Institute of Water and Atmospheric Research (NIWA) announced on Thursday
WELLINGTON, (APP - UrduPoint / Pakistan Point News - 29th Jul, 2021 ) :Flood flows on South Island's Buller River this month were the largest of any river in New Zealand in almost 100 years, the National Institute of Water and Atmospheric Research (NIWA) announced on Thursday.
NIWA hydrodynamics scientist Richard Measures said records show even larger flooding of the Buller River in 1926.
These measurements, coupled with surveys of the riverbed level carried out from a jetboat after the flood, provided the data for flood flow calculations at the bridges. As the bridges were being closed, the measurements showed a flow of 7,640 cubic meters per second, the largest direct measurement of river flow ever completed in New Zealand.
The previous record was a flow measurement of 5,870 cubic meters per second taken in the Grey River in 1988. As a comparison the mean flow of the Buller River is 454 cubic meters per second.
Meanwhile, a NIWA monitoring station on the Buller River at Te Kuha, about 10 km upstream, was continuously recording water levels throughout the flood. The monitoring station is part of NIWA's national network of benchmark hydrometric monitoring stations as well as being a key flood forecasting site for the West Coast Regional Council.
Because of its importance, the site has three independent monitoring systems in place - one sensor system to provide rapid updates during floods, plus Primary and back-up sensors to record data for future analysis.
However, the magnitude of the flood meant debris knocked two sensors out of action, leaving only the back-up providing real time information to inform emergency management decisions.
The water level at Te Kuha peaked at 12.8 meters at 1:35 p.m. on July 17, several hours ahead of the peak flooding in Westport. In the 1970 flood the flood peak was 11.9 meters. This was the biggest flood recorded since the Te Kuha monitoring site was established in 1963.
"We can confidently say that the recent flood flows in the Buller River are the highest of any river in New Zealand since 1926, when historic records and photographs of flooding show an even bigger flood on the Buller," Measures said.