Flood report recommends Regional Watershed Master Plan

Hosting a public information session about the June 23 flood in Harriston is among the recommendations in an “After Action Report” presented to Minto council on Sept. 7.

The public meeting would be hosted by the Maitland Valley Conservation Authority (MVCA) and the Town of Minto, and supported by the County of Wellington, states the report from Wellington County emergency manager Linda Dickson.
The flood itself, the response and the aftermath would all be covered at the meeting, which would also provide a forum for feedback from the public.
“Town of Minto staff and supporting agencies worked throughout the six days to not only deal with the immediate flooding but recovery efforts as well,” states Dickson’s report.
“Efficient actions by town staff resulted in normal municipal operations resuming within two to three days after the flood waters had receded.”
The report explains heavy rainfall during the early morning hours of June 23 resulted in widespread flooding throughout Minto, with the largest impact being on 168 properties in Harriston.
An emergency declaration by Mayor George Bridge on June 23 lasted for six days. The Emergency Operations Centre met five times during the event.

MVCA flood forecasting data showed the North Maitland River watershed received precipitation of 110 to 170 mm over a six- to eight-hour period early on June 23. The report states about 168 properties were damaged with current damage estimates ranging from $5 million to $15 million dollars.

Over 21 sections of various municipal roads were closed throughout the event, including three of four main access points to Harriston.

The town’s sewer and water systems remained functional during the flood, although the Young Street sewage lift station was bypassed due to the volume of flow and was eventually shut down as floodwater approached electrical infrastructure.

A boil water advisory, which lasted six days, was issued as a precaution “although at no times did supply exceed any biological or chemical parameters,” the report notes. Minto Fire and volunteers distributed about 800 cases of donated bottled water.

Minto Fire’s water rescue team was deployed eight times to rescue residents from houses.

The trailer park was evacuated as well as homes on George and King Streets. Many businesses on Main Street were also affected. Two homes in the municipal trailer park are no longer habitable.

All three Minto Fire stations were deployed to assist during the event and the recovery as water was pumped out of low lying areas. The town municipal office, Harriston public works building and recreational infrastructure were damaged.

The After Action Report indicates there were two waves of flooding that impacted Harriston. The first was based on intense rainfall received in a very short period of time.

It took time for the storm sewer system to respond to the volume of water received. Water was reported in areas of Harriston that have never experienced flooding in historical records.

Town of Minto officials fully expected the water to flow in typical paths documented in previous, less significant floods. However the intensity of the rainfall caused the water to pool in low areas. This pooling is what triggered the initial response from town staff.

The first wave of flood waters began to recede and then the second wave of flooding from the river was observed at around 8am. It continued until river flows peaked at around 6pm.

Among the lessons learned is that 90 per cent of municipalities in Ontario do not have storm sewers capable of accommodating this type of severe rainfall event.

“Existing systems pre-dated current engineering design standards,” the report states. “Most storm sewers are currently designed for [once in 10-years] flood events.”

The report notes officials gained useful information to determine how the river will react in the future.

A detour map around Harriston was created with the assistance of town road staff, MTO staff and Wellington OPP officials that can be included in the flood response plan.

The social media response was high and well received by the public.

“It was a useful and effective emergency information response tool. Emergency information was done well. Having a dedicated Emergency Information Officer (EIO) in the town worked very well,” the report states.

Recommendations in the report included:

– monitoring wells should be raised and located above identified flood levels;

– to help reduce potential flooding, the town should look at surface water mitigation measures as roads are reconstructed in Harriston and other urban areas;

– establishing a municipal back flow prevention program for buildings in the regional flood plain; and

– creation of a Watershed Master Plan to look at ways to control/retain flows from flood events to ease the effects on Harriston.

The report also notes the North Ward drain has two outlets that fill up very quickly in normal heavy rains and are soon under water when the Maitland River rises during minor events.

As development of the Schickedanz subdivision proceeds, the report recommends the town investigate diverting storm water through the site if possible, and possibly removing the old rail line barrier if it helps surface water flow out of that part of Harriston.

A new location should be found for the emergency operations centre during a flood (rather than the Harriston Fire Station), the report recommends.

Also, in a flood event use of the basement of the Minto municipal office should be reconsidered due to access concerns. The basement location was not available due to storm sewer backup.

 Dickson noted the town’s Emergency Management Program Committee is requesting the events of June 23 be considered by the province to satisfy the regulated disaster simulation exercise requirement for the Town of Minto for 2017.

Minto CAO Bill White noted many local residents are still working through the process of applying for provincial disaster relief funds.

However, he said the town itself has not yet determined that municipal damages met the minimum level for provincial assistance.

“The treasurer advised we are just over $100,000 … we may not make the amount ($150,000) where we can apply for municipal funding,” said White.

Bridge credited lessons learned during a previous flood simulation exercise with helping the town minimize damage to municipal facilities.

“We wouldn’t have been long getting up to 150 (thousand) if we wouldn’t have cut off the power to our main vaults … we would have blown up those motors we wouldn’t have got back on line like we did,” said Bridge.

“That’s probably why we don’t have two, three or four hundred thousand dollars worth of damage.”

Bridge said the simulations also pointed out the need for water rescue capability.

“If we wouldn’t have done the exercise we did a year or two before … with the idea of what would happen in Harriston if we had that kind of water and the flooding and the islands and all that, we wouldn’t have had the water rescue unit,” said Bridge.

The mayor pointed out the rescue water craft was primarily paid for with funds raised by local firefighters through efforts such as the annual Touch-A-Truck event in Harriston.