Meteorologist at flood meeting
Emergency coordinators, municipal staff hear Warning Preparedness Meteorologist Geoff Coulson speak on wetter weather, tools to get advance warning of weather
Flood emergency planning meeting told major floods not expected this spring but agencies need to be ready to respond to weather changes
Emergency coordinators and municipal staff were among close to 30 attendees at an annual flood emergency planning meeting hosted by the Ausable Bayfield Conservation Authority (ABCA) on Thursday, March 10, 2016 at the Masonic Hall in Exeter. There were four presenters including Geoff Coulson who is well-known in newspapers and on television and radio as a Warning Preparedness Meteorologist at Environment and Climate Change Canada.
Coulson has been a meteorologist with Canada’s environment department for more than 30 years. He has been one of the two Warning Preparedness Meteorologists in Ontario for more than a decade. The presenter spoke to flash floods which tend to result from intense rainfall over a relatively small area. Floodwaters can rise and fall rapidly with little or no warning. “By the time the weather pattern has formed, the rain may be occurring already,” Coulson said. Unlike in the United States of America, Canada does not have something that is specifically called a flash flood warning, according to the speaker. In Canada, there are severe thunderstorm warnings that make specific mention of flash flooding as a concern. Land use, topography, and existing ground wetness are factors which can influence whether flash flooding will occur.
The speaker encouraged municipal staff and emergency coordinators to be mindful of all statements and bulletins that are issued by Environment and Climate Change Canada as each message that is issued starts to paint a picture of the weather event. Watches and warnings are reserved for when weather events are closer to occurring but forecasters try to provide information in the lead-up to the event. They may issue a special weather statement in the morning of what might be an active day. The watches themselves are very useful, he said, even if there is not yet enough data yet to support a full warning. “If your area is within the watch, that is something you want to be paying attention to,” he said.
Coulson spoke both of the new and improved tools that help his department to better understand weather systems but also to the challenges when localized flooding experienced by a community is not reflected in the levels detected in nearby rain gauges. Speaking to local examples, such as Seaforth and Nairn, sometimes a flash flood may hit only a small area. The forecasters may be able to predict that storms are possible in a three-county area, for instance, but the storm may only hit part of one county. “While we’re better now at recognizing the weather patterns that may lead to flash flooding, the areas we’re dealing with are still much, much larger than where a storm may actually form,” he said. When storms start to form, radar remains the number one tool they have to track the storms and to say which storms have the potential for flash flooding, he said.
Coulson has worked in weather forecasting, training, software development, and outreach. He has helped to provide targeted weather information to clients and media before, during, and after severe weather events in Ontario. He also helps to train a number of key groups in understanding Ontario weather patterns. Coulson’s clients include emergency management organizations, municipalities, federal departments, provincial ministries, and the media. He also manages the CANWARN storm spotter network in Ontario. He said these volunteers are an integral part of the Severe Weather Watch and Warning Program of Environment and Climate Change Canada.
The presenter also talked about the changing Canadian climate. He spoke to projected impacts of a changing climate including possible health impacts from an increasing number of warmer days. There is also an expected decrease in the number of extremely cold days. Climate models suggest it is likely that, as our climate continues to change, we will experience an increase in intensity and frequency of heavy rainfall events, ones that could cause flash floods. There may be flooding and watershed management challenges in the wintertime as temperatures rise with a changing mix of precipitation, more rainfall and freezing rain, a greater chance of ice storms, and potential for wintertime floods, he said.
Switching from climate to weather, Coulson said that there might be a mix of precipitation left this season but that a major dump of snow is unlikely. In effect, he said, spring is here. “The trend we’ve seen so far is for warmer than normal conditions to continue,” he said.
Other speakers at the flood emergency planning meeting included Stephen Jackson, Flood and Erosion Safety Services Coordinator with Maitland Valley Conservation Authority (MVCA). He spoke about emergency planning along the lakeshore and the threat of bluff failure. There are emergency response challenges, said Jackson, if a bluff collapses. Jackson spoke about an emergency exercise held in the Township of Ashfield-Colborne-Wawanosh, north of Goderich. He said that it was a good opportunity for fire, police and emergency medical services to familiarize themselves with shoreline hazards and response challenges.
Jackson said the water level of Lake Huron has rebounded and nearshore and lake-effect erosion is a concern. “We’re seeing this erosion this summer,” he said. Wind, waves, and currents can erode soil and sand even underwater. Land above water may appear stable but this hidden nearshore erosion can actually make banks and bluffs unstable for the homes and buildings built up above. “Every time we have an intense storm event, that really high velocity erodes the clay till and these banks are cut back,” he said. “The difficulty with bluff erosion is you can’t say ‘in two weeks there is going to be a failure,’ or ‘in a month, there is going to be a failure,’ ” but the risk remains that some shoreline structures will “end up in the lake” when erosion happens and banks collapse. Tree planting is helpful to stabilize banks but Jackson showed a slide of a failure along the shoreline illustrating that just because there are trees in place on a bank there is no guarantee there won’t be erosion or failure.
The Land and Water Technologist with ABCA, Davin Heinbuck, was the meeting’s third presenter. He outlined the results of a flood emergency messaging test exercise conducted by staff in early March to ensure flood communications systems worked well in advance of spring flood messages.
The presenter also spoke about current watershed conditions. Heinbuck noted that a Watershed Conditions Statement – Flood Outlook, Water Safety was issued on March 8 based on melting of the final snowpack and the forecast of precipitation. This winter doesn’t pose the ice jam risk of other winters and there isn’t the snow pack that poses the flooding threat of some other years, according to the Land and Water Technologist. Still, he said, a heavy rainfall between 25 and 50 millimetres would be enough to get the water rising and streams flowing rapidly. “With the really wet ground, the biggest threat right now is heavy rainfall,” Heinbuck said.
Although there is no foreseen risk of damage from ice jams this year, Heinbuck pointed to some local examples of ice jam and flood damages in recent years in areas including Nairn, Seaforth, and parts of Middlesex County. He spoke about the water levels of lakes Huron and Michigan and how they have rebounded by about a metre since the same time in 2013.
The Water and Planning Manager for ABCA, Alec Scott, was the fourth and final presenter at the meeting. He outlined agency roles and responsibilities under the ABCA Flood Emergency Plan. His talk included some of the provincial responsibilities, municipal responsibilities to deal with flooding, and conservation authority responsibilities for flood forecasting and warning and providing information to support municipal response efforts. “Flooding does happen,” Scott said, showing slides of different flood events in recent years. There can be stretches of time when there are very few flood events but then several flood events can happen close together, he said.
Scott outlined the three different levels of flood messages:
Watershed Conditions Statement – Flood Outlook, Water Safety
Flood Watch
Flood Warning
Flood messages are posted at abca.on.ca. He outlined conservation authority programs that help to prevent and reduce flood damage, including emergency planning; flood forecasting and warning; erosion control projects; dam operation; regulations; and plan input and review.