Spike in water flowing over Albion Falls that stranded hikers was steep but not unusual

The torrent of water cascading over Albion Falls Monday that trapped hikers was not above normal high flows.

But while the amount of water was not unusual, the increase in water flowing over the falls after a thunderstorm hit the Mountain was steep and rapid.

Flows in the Red Hill Creek below the falls were at 1 cubic metre per second at noon, before the storm. But within two hours had spiked to 30 cubic metres a second. Over that same period, water levels in the creek rose by a metre.

Jonathan Bastien, who overseas water resources engineering for Hamilton Conservation Authority, says there was quite an increase in the water flow rate after the storm, and that that kind of response after a big storm is typical of both Albion and Chedoke falls, the two locations where hikers were stranded.

It was a steep increase in a short period of time, but Bastien says that the base flow tends to be quite low, especially in the summer time, making Monday's measurements smaller on the grand scale of things. 

"It's natural for the creek to respond with significantly higher flows as it gets a storm event where it's collecting and running off to the water course," said Bastien.

The figures are collected from the Red Hill at Barton Street, just downstream from Albion, but Bastien says they capture the increase in flows that are occurring at the falls.

Bastien describes Red Hill as a "flashy" system—meaning that it changes quickly with rapid increase of water.

The rain started at noon, with the flow rate peaking at 2:00 p.m., going back down at 6:00 p.m.

Bastien says it got back down near base flow conditions within about three or four hours after the peak.

"It certainly wasn't like a historic flow that has never occurred there before, and it certainly isn't like the highest flow usually ever year. It's below those kind of thresholds," said Bastien. "It's certainly not like the maximum we would expect to see you know, on average, each year." 

Water levels at Red Hill at Barton Street remained just below what is set up as their early alarm levels with regards to watercourse flooding.

It was about 15 cm below the alarm level says Bastien.

There have been other dates this year where water levels rose higher than Monday's, but Bastien says the higher levels are typically seen in the springtime, with the winter melt.

What's unique about locations like Chedoke and Red Hill is how they respond to rainfall. 

Bastein says they both respond quickly to storms, which means there's likely to be noticeable changes to levels within hours.

This is in comparison to a place like Spencer Creek where it's more likely to take a longer period, even days to see an increase in water levels in Dundas. This is because of the length of the creek and travel time for the water to reach the creek. 

It's based on factors like size, shape, type of land, and amount of urbanization.

When it rains, you'll see high levels in the watercourse where with others, it may take a day or half a day to start to see an increase.

On Monday the substantial rainfall in the Hamilton area stranded 10 hikers at Albion Falls and a family of five at Chedoke Falls.

The group of hikers at Albion Falls had been unable to safely ascend the falls due to the sheer amount of water that came down, Hamilton Fire spokesperson, Steve McArthur told CBC News Monday.

It's unknown what the levels were at Chedoke Falls where the family became stranded as the deluge of rain surrounded the rock they were on. Bastien says there isn't flow data available for Chedoke Creek because there isn't a gauging system setup there.