Dams have become an integral part of Ontario’s waterways providing numerous benefits to Ontarians such as hydro electricity generation, water for irrigation, as well as supporting a wide range of recreational opportunities. As we boat, fish and hike near dams we must do so in a manner which does not place ourselves or loved ones at risk. It is important for everyone to educate themselves on the hazards created by dams and to keep these hazards in mind as you enjoy the beauty that Ontario has to offer.
Dams in Ontario
A dam is defined as “a structure of work forwarding, holding back or diverting water”. A dam can take many forms such as a low head weir, a hydro-electric generating station, a concrete dam with removable stop logs or adjustable gates, and a marine navigation lock.
There are over 2,500 dams throughout Ontario ranging in height of less than one meter to over one hundred meters. Dams are owned by a variety of industries, municipalities, Conservation Authorities, private landowners and the Province of Ontario. Historically dams were built for industrial uses such as mills, logging and navigation. Currently, dams provide hydro-electricity production, municipal water supply, flood management, wetland habitat management, low flow augmentation, navigation and recreation opportunities.
Hazards Associated with Dams
Regardless of their size, type of construction or intended use, all dams present certain hazards to those who work or play near them. Dams with associated public uses are assessed for hazards which may be present risks to public safety. Signs, booms, buoys and fencing are methods used to warn and protect the public from these hazards.
What are the hazards?
- While low head weirs may appear insignificant, they pose considerable dangers to those boating or playing around them. Water that continuously re-circulates at the base of low head weirs creates underwater hydraulics which can easily trap someone at the base of the dam. This hydraulic effect is commonly referred to as a 'drowning machine'.
- Low head weirs may have no visible structure above the water line. Boaters approaching a weir from the upstream side may not be aware of the dangers present. Boaters should always watch for and obey signs, booms, buoys, and portage markers.
- Upstream dam leakage between and around stop logs may suck in a swimmer and hold the person below the water level with such force they cannot escape.
- Objects in foaming water are less buoyant than still water. Air trapped in water reduces the buoyancy and therefore persons caught in such conditions have greater difficulty staying afloat even with the aid of personal floatation gear.
- Changing water levels and flows below a dam can occur rapidly and without warning. Never place yourself in a situation where you cannot leave the area you are boating in or have accessed by boat. Never camp, picnic or sunbathe in an area below a dam which may become flooded.
- Concrete retaining walls above and below dams could block exit routes for individuals trying to escape the dangers associated with a dam. These are often present around marine locks.
Seasonal Dam Safety Tips
- Always stay outside booms and away from all dam structures.
- Never swim above a dam or dive from a dam structure. Currents can pull you through the dam or pull you against flow structures with such force that you could not escape.
- Never fish, boat, or swim below a dam. Water levels and flows can change very quickly and you may not be able to react in time to avoid the danger.
- Personal water craft and boats should always stay clear from dams. Never moor, tie or anchor your boat below a dam.
- Never sunbathe, picnic or camp in an area which may become flooded due to dam operations.
- ATVs should be used with caution around water. Operators should be aware of possible changes in water flows or levels from dam operations.
- Always obey posted signs, and do not enter fenced areas to hike, or access hunting or nature viewing areas.
- Beware of thin ice that may develop due to dam operations. Never venture out on the ice alone. Always wear a floatation suit and carry a throw rope.
- Dam operations often result in lowering of water levels throughout the winter and spring. However, this can result in ice collapsing onto lower water levels and then water seeping up under the snow. Persons venturing out on the ice should always be aware of the potential of slush under the snow over ice. Travel in slush conditions is very difficult regardless of the mode of travel.
- Persons fishing should stay clear of dams. Water flows and levels can change quickly.
- Canoers and kayakers should always stay clear of dams.
- Stay off the dam structures unless the area is clearly marked for public travel.
- Be alert to changes in water levels.