Flooding throughout northern Huron County tests preparedness - June 29, 2017
BY DENNY SCOTT
The Blyth Creek was at its highest level in 40 years as the village saw the second-highest amount of precipitation in the Maitland River watershed during a flood-causing, intense rain event on Thursday, June 22.
Maitland Valley Conservation Authority (MVCA) Communications Director Jayne Thompson explained that, on Thursday, June 22, a storm started that would see communities in the MVCA’s area experience as much as 180 millimetres of rain overnight.
“We had a significant, intense rain storm that came through the area overnight on June 22,” she said. “Depending on location throughout the area, the storm hit between 10 p.m. and 5 a.m. Harriston then received more rain between 5 a.m. and 7 a.m. on June 23.”
Thompson said the storm presented a very narrow, but intense band of rainfall and that Harriston was the hardest hit with areas in the community receiving between 160 and 180 millimetres of rain.
“That was a huge amount for that short period of time,” she said.
Other communities also saw significant rainfall including Blyth receiving 130 millimetres of rain, Wingham receiving approximately 102 millimetres, Wroxeter receiving 70 millimetres and Bluevale receiving 90 millimetres.
“When we see that amount of rain, we get really fast run-off into the river system,” Thompson said. “The bulk of significant flooding as a result of that was in the north Maitland Branch.”
The water overwhelmed dams and taxed flood plains throughout the area, including the Gorrie dam, which Thompson said worked exactly as designed.
“What happened in Gorrie was the dam did what it was designed to do,” she said. “That may sound odd, but it was designed in such a way that, if the flow exceeded the capacity of the dam, it would go over a berm on the south side of the dam and go into an emergency spillway.”
Thompson said that was exactly what happened. The berm was gradually worn away and the water flowed into the emergency spillway.
“The good thing in all that happened was that the dam worked as expected and the berm was slowly broken down by the water,” she said. “Thanks to that, there was not a sudden burst of water. The water slowly made its way down the Maitland and got held up at Victoria Street in Gorrie before making its way through Wroxeter and Wingham.”
That huge surge of water was a significant concern for the MVCA, Thompson said.
“Although the level did certainly rise... the flood plain in Wroxeter was able to handle and absorb some of that water and slow it down as it made it’s way to Wingham,” she said.
Flooded areas, roads and homes could be found throughout the area and, locally, the Blyth brook was at the highest level it has been in 40 years of data collection, Thompson said, while the Brussels dam was completely under water.
“It was interesting for us to see that height in Blyth,” she said. “The creek bottom varies so much, so we can only measure by looking at how far it came out of the banks and into the flood plain. It went higher onto the plain than ever before.”
For the MVCA, the flood may be over, but the work is just beginning.
“As the levels are dropping over the next couple days, MVCA staff will be visiting the dams we are responsible for; Gorrie, Brussels and Bluevale,” Thompson said. “We will be having a look at the damage that may have been caused.”
The MVCA is already aware of damage that the Bluevale dam suffered and all the boards that hold the water back will need to be pulled out.
“We will be looking at the dams, assessing the damage and developing options on how to proceed,” she said. “We don’t have information about what our future actions will be yet.”
Thompson said people have already asked if the berm near Gorrie will be repaired, however the MVCA doesn’t know the extent of the damage, Thompson said.
“We will make that information available as we work through the process,” she said.
That process will involve the Ministry of Natural Resources and Forestry, Thompson said, as they will need to weigh in on the situation and the repairs.
While this was a significant event, Thompson said, on a regional basis, it didn’t match the 100-year-storm mark that the MVCA encouraged developers to think of.
“To put that into context, that’s still nowhere near a regional event,” she said. “We use Hurricane Hazel as our regional event. During that hurricane, there could have been twice as much rain as what we got over the weekend.”
She said they don’t use what happened in Huron County during the hurricane in 1954, but what would have happened had the hurricane been directly over Huron County.
“The storm last week, however, was a really significant event,” she said. “As we look at our weather trends, we will likely have more of these kinds of events that include short but very intense storm rains.”
Thompson said the municipalities involved responded well.
“The municipalities stepped up to the plate and did a terrific job,” she said. “There was no loss of life, which is great. There certainly was some property damage to our own infrastructure as well as houses and roadways, which is never good, but for the magnitude of water that came down, it could have been worse.”
The MVCA has been focusing, in recent years, more on flood prevention and warning programs and Thompson said she believes the system worked as intended.
“I would say we felt we were better prepared and able to give our municipalities notice of the event,” she said. “There is always room for improvement, however. [On Monday, we had] a long series of discussions about how we can fine-tune and improve the flood forecasting system.”
Thompson said the short, intense rainstorm events are more difficult to predict and shorten the timeframe the MVCA has to warn municipalities and the time the municipalities have to react.
“It’s different from the spring floods when we know the snow pack and can see the rain and warm weather and do modelling based on that,” she said. “These events are very different animals and present a lot of challenges.”
One concern that came up during the event, according to Thompson, was the danger that comes with the higher water.
“We had a very close call in Gorrie where people tried to canoe over the breach created when the berm broke,” she said. “The canoe is very badly damaged and somewhere on the river, but the people in it got out of the water safely. We do need to work on reminding people that, during a flood warning, it’s not a good time to do activities around the water. People need to stay away from the rivers.”
What to do after the flood is also a concern, according to the Huron County Health Unit, which issued a press release on Monday about what actions to take after flooding.
Public Health Inspector Mike Park encourages well owners in flooded areas or those that received heavy rain to test their water.
“Wells in low-lying, flood-prone areas are at risk for contamination from surface runoff,” Park said in the release, adding that dug wells, well pits and well casings without proper seals are most at risk.
Any water that has an odour, discolouration or tastes badly should not be consumed or used for food in preparation.
All water should be tested, according to the release, and anyone unsure of the safety of their water should be boiled for at least one minute prior to drinking or using for food preparation.
The Health Unit provided the following tips for water safety after a flood event like the one that occurred late last week.
• Be sure septic tank covers are secure.
• Do not use sewage systems until the water level in the soil absorption field is lower than the water level around the house.
• Have septic tanks inspected professionally if damage is suspected.
• Do not drive heavy equipment over the soil of the absorption field as it’s vulnerable to compaction.
Backed-up sewage should be cleaned and disinfected with a chlorine solution of one half-cup of chlorine to each gallon of water.
• Discard any food that may have been touched by flood waters except for commercially-canned foods.
• Undamaged, commercially canned foods can be saved if the label is removed and the can is washed thoroughly and disinfected.
• Foods with twist-off caps such as sodas, juices or sauces should be discarded as they cannot be adequately disinfected.
• When in doubt, throw it out.
When cleaning up after a flood, minimize contact with floodwater or anything that was in contact with the floodwater and keep children away from contaminated areas.
Follow these steps for a safe clean-up:
• Prepare for the cleanup by gathering necessary supplies including gloves, N95 masks, rubber boots, goggles, soap, pails, dehumidifiers and wet/dry vacuums.
• Vent the affected areas by opening windows and doors.
• Remove water, mud and other debris including standing water, dirty material, debris, soil and residual mud.
• Use soap and water to clean all affected areas.
• Ensure all cleaned areas are allowed to dry as quickly as possible.
• Dispose of household items that cannot be dried within 48 hours as anything that takes longer has greater potential for mould growth.
• Items such as insulation, drywall, carpets, particleboard furniture, beds, toys and cushions that have had contact with flood waters and cannot be dried should be discarded.
• Clean and dry out your house and salvageable possessions using fans, heaters and dehumidifiers to speed up the drying process and prevent mould growth.
• Vacuum surfaces that are dry and/or have not been directly affected by the flood waters with a HEPA vacuum cleaner.
For more information on how to treat areas affected by mould, visit the Huron County Health Unit online at huronhealthunit.ca.