Flood — Grant, South Dakota

2023-04-12 · near Milbank Arpt, Grant, South Dakota

Event narrative

The South Fork Whetstone River gauge near Milbank peaked just above flood stage at 1113.83 feet, with water reaching the bottom of the bridge on 148th Street. Otherwise the impact was mainly to agricultural lands.

Wider weather episode

After a consistently cold early spring with below-average temperatures and frozen soils, a mild period of weather emerged during the second week of April. The deep snow cover, exemplified by Milbank's report of a 17-inch snow depth on April 1st, along with a snow water equivalent exceeding 4 inches, rapidly transitioned into liquid form. This substantial snowmelt flowed into the waterways, leading to flooding along the Whetstone River. The South Fork Whetstone River gauge recorded a peak just above flood stage at 1113.83 feet, with water reaching the bottom of the bridge on 148th Street. On the evening of April 15th, the North Fork Whetstone River near Milbank gauge site reached a moderate flood stage of 1062.40 feet, resulting in water overflowing onto 479th Avenue and surpassing the bridge on 144th Street. Two other bridges were also affected as water levels rose. A significant portion of agricultural land was impacted. The Whetstone River gauge above Big Stone City registered a peak of 19.65 feet on April 13th, just below the threshold for a major flood stage.

A Presidential Disaster Declaration was approved for Brown, Clark, Codington, Day, Faulk, Grant, Hand, Marshall, Potter and Roberts Counties, as well as for the Lake Traverse Indian Reservation, where an estimated $2,305,362 in total qualifying costs were incurred during spring flooding.

View location on OpenStreetMap → (45.2500, -96.5600)

Source: NOAA Storm Events Database, event_id 1089297. Narrative written by the NWS forecast office that issued the report.