The Red River at Fargo crested Saturday at 40.82 feet, breaking a record of 40.1 feet set in 1897. The river’s level has begun to decline but it is only expected to fall to below 36 feet (twice flood stage level) by next week. President Obama has declared emergencies in the affected regions in North Dakota and Minnesota, freeing up federal aid money. The communities have done an amazing job of coming together- packing and stacking millions of sandbags amongst other flood preparations.

It is unknown what effects (if any) a snowstorm that moved into the region yesterday will have on the river’s levels. But assuming the best- that the area is safe for the time being- there is still cause for concern. The Red River at Fargo has been experiencing what are known as “ten year floods” nearly every two years over the past two decades. 

“Ten year” floods (and the similarly named “one hundred year” variety) are a misnomer in that they are not floods that are expected to occur once in that given time interval. A “ten year” flood has a 1 in 10 chance of occurring each year. 1/10=.1 so there is a 10% chance each year and a 65% chance of it occurring in a decade. The same applies to the “one hundred year” floods with the numbers being 1% per year and 63.4% per century.

The rates that define these floods varies between rivers and is calculated based on previous flood data. There is a United States Geological Survey river gauge at the flood point in Fargo that measures streamflow (in cubic feet/sec or cfs) and height (in feet). The most recent flow measurement was at 21, 800 cfs with a height at 38.03 feet. A “ten year flood” has a flow above 10, 300 cfs. To be considered a “one hundred year flood”, the cfs would need to be above 29, 300. Early Saturday morning, the Red River peaked at a flow of 29, 400 cfs. It stayed at this level, though somewhat inconsistently, for four hours.

What is causing the flood recurrence in the Red River? Part of the problem is geography:

The Red River Basin is unique because the mainstem of the Red River flows north into Canada and eventually into Hudson Bay. Consequently, the spring melt, and the eventual runoff, differs from many other areas of our county. (as a side note, the Red River is not the only river in the United States which flows north, there are others such as the Genesee River in Upstate New York). In a typical spring thaw, warmest temperatures and initial runoff begin in the source region of the Red River, over Northeast South Dakota and West Central Minnesota. After this runoff enters Lake Traverse it begins to travel north. Weather conditions farther north or downstream, however, are usually quite different from those of the headwater region, with melting and runoff yet to begin.

Because of the relatively flat slope of the valley, the flow of the Red is slow, allowing runoff to backfill into tributaries, particularly when the downstream river channel remains frozen. In addition, localized ice jams, may impede the water flow, resulting in higher river levels.  

There are also environmental conditions that factor in: 

1. The freeze/melt cycle

2. Early spring rains which increase melting of the snow pack or late spring snow storms adding to the existing snow pack

3. The actual snow pack depth and water equivalency

4. Frost depth

5. Soil moisture content

6. River ice conditions

Increased precipitation is one of the major side effects of global warming. President Obama mentioned last week the correlation between climate change and future Red River floods: 

He said, “I actually think the science around climate change is real. It is potentially devastating. … If you look at the flooding that’s going on right now in North Dakota, and you say to yourself, ‘If you see an increase of 2 degrees, what does that do, in terms of the situation there,’ that indicates the degree to which we have to take this seriously.”

The people along the Red River obviously can’t counteract global warming on their own. The best they can do is keep watch on the levees and dikes and prepare for the worst in times like these when flooding is a threat. The NSGS will keep monitoring the stream gauge for changes if their funding doesn’t get cut.

But these environmental aspects of the Red River story are not likely to make the news. The media wants to focus on the “human interest” side of the story. Which is all well and good except those interesting humans are going to keep facing floods of increasing intensity unless something is done about it.