Summer safety alert: Beware of rising river levels and unpredictable weather
Environment Canterbury media release: 17th December 2024
Before you head to your favourite river this summer, check for weather warnings - some weather patterns can cause rapid rises in river levels.
Our duty flood controller, Chris Fauth, advises that if you’re spending time around Canterbury’s rivers or lakes, you need to be aware of forecast rain in the headwaters of the Southern Alps.
The strong, hot, dry wind of Canterbury’s infamous nor-westers usually means heavy rain in the upper reaches of our alpine rivers such as Waiau Uwha, Hurunui, Waimakariri, Rakaia, Rangitata, Waitaki (and Waitaki Lakes) and Ahuriri.
"It may be a beautiful day in the Waitaki Valley, or out boating on the Rangitata River, yet it could be pouring with rain back in the mountains."
"The water has to go somewhere, and the result is usually one to two days of higher flows and changeable river patterns out on the Canterbury plains. Thats why checking the weather forecast and river flows regularly is important. We want people to enjoy their summer and to stay safe," Chris said.
Rapid changes in river flow patterns can result in surprises
At this time of year, vehicles can get stranded and are sometimes even washed downstream.
Dry areas of the riverbeds, crossed early in the day, can quickly carry flows as braided flow channels move about the riverbed. Sometimes this turns accessible areas into river islands, preventing people from safely exiting the riverbed later in the day.
Hydro lake spills can impact river levels
Summer rain can also increase the possibility of spill flows from our hydro lakes into rivers. The upper Waitaki Lakes are currently just below levels where this may occur; however, this may change if further seasonal rainfall occurs in late December and early January.
Check before you go
Flow channels that were low or dry can rise quickly, preventing people from safely exiting the riverbed.
"It can happen so quickly. The problem is that people aren’t checking weather conditions in the mountains before they rock on down to the river," Chris said.
Where to check:
No matter what you’re doing in or around our rivers this summer season, be aware of weather forecasts and, if in doubt, keep out.