Hazards can change from day to day and sometimes within hours due to weather and water conditions. Prepare for changing conditions. Check weather information and communicate with local people about what local hazards exist. Rainstorms can lead to rapid rises in river water levels, cause debris to accumulate, and create strong currents and large waves. Boaters should always be careful around any kind of debris or man-made structure. Debris or downed trees in the water can create an entrapment hazard, a leading cause of death among human-propelled boaters.
Low-head dams, often called drowning machines, can cause very strong currents above and below the dam and strong recirculating current at the downstream base of the structure. Once swept over the dam, a victim can become trapped and forced underwater, pushed away from the dam, then circulated to the top. This strong hydraulic motion makes it nearly impossible to escape. If trapped in a low-head dam situation, tuck your chin into your chest, draw your knees up, and wrap your arms around them. Conditions may push you out of and away from the hydraulic current, along the streambed. It is always best to portage around dams on any river or stream.