What are the hazards? (source: Ontario Ministry of Natural Resources)

  • 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.
For more details see "Public Safety Around Dams"