A 1-in-100 to 1-in-200 year flood is in progress in North Dakota along the Souris River, where flood heights never seen in recorded history are putting unprecedented pressure on the river’s levees. The Lake Darling flood control reservoir located about 15 miles upstream from Minot, North Dakota, the state’s 4th largest city, is full to overflowing. Record releases of water are occurring to prevent the lake’s dam from overtopping. A mandatory evacuation of 11,000 residents from Minot is underway, and must be completed before Thursday morning, when water levels on the Souris River are expected to rise several feet above the previous all-time flood height, set in 1881. Massive rainfall in Canada on Sunday and Monday, combined with very heavy rainfall and snow melt over North Dakota over the past month, are responsible for the record flood. The Souris River Basin near the Rafferty Dam in Saskatchewan received four to seven inches of rain Sunday into Monday. Flood heights along the Souris River near the Canadian border upstream from Minot are already almost a foot above the previous all-time highest mark, and all that water will arrive in Minot beginning on Thursday, likely overwhelming the city’s levees and flooding large portions of the city for two or more weeks.

Figure 1. Observed (blue line) and forecast (green line) stage of the Souris River in Minot, North Dakota. The river is currently at its 4th highest level on record, and is expected to rise above the record flood stage of 1558′ Thursday night. The record was set back in 1881. Image credit: NOAA AHPS.

Figure 2. The Souris River (in pink) is part of the Red River drainage basin. Image credit: Wikipedia.

Heavy rains this week over the neighboring Missouri River watershed forced the Army Corps of Engineers today to increase the flow rate at the key Gavins Point Dam to a record 160,000 cubic feet per second. The dam was already releasing water at more than double the previous record flow rate, and the increased flow is expected to raise flood heights by 0.3 – 0.7 feet along the Missouri River from Omaha to Kansas City. There have already been two levee failures and two places where levees have been overtopped along the Missouri River this month, resulting in large-scale flooding of low-lying farmlands. “This continues to be a very dynamic situation and dangerous at the same time,” said Brig. Gen. John McMahon, commander of the Northwestern Division of the Army Corps of Engineers.

The Atlantic is quiet
The Atlantic is quiet, but several models, including the NOGAPS and GFS, are predicting that a tropical disturbance capable of becoming a tropical depression could form near Mexico’s Yucatan Peninsula about seven days from now. In the Eastern Pacific, Hurricane Beatriz is gone, after being torn apart by Mexico’s high mountains during landfall. Beatriz is responsible for at least three deaths in Mexico.

Jeff Masters