In the gym, Prof John was telling us to be careful during winter. Every year, someone will surely fall down to drain and die. In the winter, snow got so thick that it's almost impossible to differentiate drain from the normal flatland.
2 years ago, they found a body of a local people in the Urasa river. John said that the people must have drank too much, and then when they go piss, they went far away from the rest of the group, ventured to loose ice on river bank and fell into the river when the snow collapses.
Therefore it is always a good idea to stay as far away from river banks as possible.