In the 1871 Canada Census, we have 30 year old surveyor Arthur Hamilton living in Ottawa City with his wife, Janet, and two young children.

In 1872, the time of the accident, Arthur would have been 31 years of age, so the notation wording of "31 drowned" is actually meant to indicate his age, not the number of drowning victims.

A search for the children in the 1881 census (under the assumption that they would have retained the HAMILTON surname, even in Janet had remarried) turns up one potential family still living in Ottawa, but in Victoria Ward. The head of the household is Jane HAMILTON, a widowed housekeeper. There are two children living with her with ages consistent with the '71 census family with the exception that the son is named Edwin instead of Arthur.

Perhaps the names and ages of the wife and children may be a clue to the connection with your family, KWurtzel.