Flooding along the Red River is not an exception; it is the rule. The river follows the bed of Glacial Lake Agassiz, a massive Pleistocene lake that left behind some of the flattest terrain on Earth. The valley's gradient is so gentle that the Red drops only about one foot per mile across its entire length. When water rises, it spreads sideways rather than running downhill, and there is nothing -- no bluffs, no significant elevation change -- to contain it. Winnipeg has recorded major floods in 1826, 1852, 1861, 1950, 1997, and 2009. The 2011 event did not match the worst of these, but it carried its own menace: forecasters warned that the Red and the Assiniboine rivers might crest in Winnipeg simultaneously, a dual punch that could overwhelm the city's flood defenses.

While the Red River drew the headlines, it was the Assiniboine that delivered the most extreme conditions. At Brandon, Manitoba, the Assiniboine reached its highest-ever recorded level, a magnitude classified as a 300-year flood -- meaning such an event has roughly a 0.3% chance of occurring in any given year. The Assiniboine's surge fed directly into the Red River system, pushing the combined crest at Winnipeg's James Avenue pumping station to 19.59 feet above datum. That number told a layered story: 2011 levels on the Red itself were actually below those of 2009, but the Assiniboine's contribution elevated the combined reading to dangerous heights. Officials later calculated that without the floodway and diversion channels constructed in the 1960s and later, the 2011 crest would have amounted to the sixth-highest water level in Winnipeg's recorded history.

The human toll accumulated in small, devastating increments. Around April 8, an ice jam in St. Andrews, Manitoba sent the river over its banks, forcing the evacuation of 50 homes and flooding two more. Three fatalities in the United States were attributed to the flood by that same date. One man died while sandbagging in the Fargo-Moorhead area, exhausted and overwhelmed by the relentless labor of piling wet sand against rising water. Two other men drowned in the Maple River in North Dakota when their boat capsized while they were hunting beavers -- a reminder that floodwaters do not announce their boundaries clearly. The following day, a fourth victim perished in Niverville, Manitoba, when his vehicle skidded off a flooded road and submerged before he could escape. Four lives lost across two countries, each death a separate story of misjudgment or misfortune played out against water that refused to stay within its banks.

The 2011 flood became, in part, a vindication of infrastructure. Winnipeg's Red River Floodway -- a 29-mile diversion channel excavated in the 1960s that routes floodwater around the city -- proved its value once more. Without it, and without the Portage Diversion on the Assiniboine and the Shellmouth Dam upstream, the 2011 crest would have placed alongside the catastrophic floods of the 19th century. The floodway had already justified its existence during the 1997 Red River Flood, nicknamed the 'Flood of the Century,' and again during the 2009 flood. Each event strengthened the case for the massive public investment. But the 2011 flood also exposed limits. Downstream communities lacked comparable protection, and the Assiniboine's record-breaking surge showed that the river system could still produce surprises. The flat, memory-laden landscape of the Red River Valley will flood again. The only questions are when, and whether the defenses will hold.