Flood in Roberts County, South Dakota

The South Dakota Department of Transportation reported water over the roadway.

On June 25th, multiple thunderstorms from the morning into the early afternoon caused flooding in parts of northeast South Dakota. A CoCoRaHS observer 4 miles south-southeast of Milbank recorded 3.33 inches of rain, while the COOP observer in Milbank measured 3.25 inches. Grant County Emergency Management sent photos of washed-out roads, and a resident near Ortley documented water reaching a home's foundation.

The heavy runoff caused several area rivers to flood. Near Milbank, the North Fork Whetstone River began flooding on the morning of June 26th and remained above flood stage until the afternoon of the 28th, cresting at 1058.11 feet. The nearby North Fork Yellow Bank River also flooded during this time, cresting at 1043.03 feet, or 2.03 feet above flood stage. The Big Sioux River near Florence flooded from June 26th until the afternoon of June 29th, with a peak crest of 8.96 feet. Additionally, a tributary of Mud Creek near Rauville flooded from the morning of June 26th until the morning of the 28th, reaching 4.3 feet.

This runoff, combined with more rain, caused additional flooding downstream on the Big Sioux River. The river briefly flooded near Watertown early on June 28th. Farther south, the river near Castlewood began flooding early on June 29th, cresting at 9.59 feet before falling below flood stage on the evening of June 30th.