Flood in Minnehaha County, South Dakota

Snow melt and heavy rainfall (measured 2.74 inches at Hartford, 2.25 inches at Colton, and 2.49 inches at Sioux Falls) resulted in extensive flooding of the Sioux Falls park system near the natural channel of the Big Sioux River around the southern side of Sioux Falls. Water, and the broken ice cover from the river system, caused extensive damage to city property with numerous bridges and buildings completely destroyed, equipment damaged, and miles of bike trail washed out. Around 80 homes were inundated by floodwater with evacuation of 17 residents and their pets, as water reached the highest levels since construction of the homes. Water filled the tunnel on 57th Street under Interstate 229, flowed onto several portions of Interstate 229, and over 26th Street east of Interstate 229 and Cliff Avenue south of I-229. The Big Sioux River at Western Avenue (gage site WAVS2) reached the highest stage on record cresting 9.15 feet above flood stage on March 14. The river remained at minor flood stage at the end of the month. Property damage costs are rough estimates.

A historic flooding event unfolded as heavy rainfall drenched the area on March 13-14, 2019. With frozen and impervious ground, full and rapid runoff was maximized. In addition to the rainfall, between 1 and 3 inches of snow water equivalent remained in the snow pack south of Interstate 90, with 3 to 6 inches of snow water equivalent north of Interstate 90. Fifteen river gage sites measured record stages around the area. Winds gusted to 50 to 70 mph at times, and colder air filtering into the system at the end of the storm produced a light accumulation of ice west of the James River and from 1 to 4 inches of snowfall in parts of southeast South Dakota.