Heavy rains of 8 to 12 inches that occurred on July 22-24 along and north of the Highway 20 corridor between Waterloo, IA and Dubuque, IA resulted in record flooding on the Maquoketa River and Lake Delhi (also called Hartwick Lake). The pressure from the record river flood levels were too much for an earthen berm on the south side of the Lake Delhi/Hartwick Lake Dam. It gave way shortly after 1 pm July 24.
48 Hour Rainfall Totals Ending ~7AM July 24
Hydrograph of the Maquoketa River Level at Manchester Highway 20