Primed by 1 to 3 inches of rainfall on June 17-18, starting June 20, the area was impacted adversely by several very slow moving mid-level waves which drifted across the northern and central Plains during the following week. High precipitable water and persistent lift forcing resulted in a widespread 4 to 9 inches of rainfall, inundating crop and pasture land as well as damaging infrastructure.

Flood in LYON, IOWA
From 20-JUN-18 23:00:00 to 29-JUN-18 11:00:00 (CST-6)
Location: ROCK RAPIDS MUNI ARP
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

A week of periodic heavy rainfall ending June 26 resulted in a widespread 5 to 10 inches of rainfall, much of which occurred on June 20, 24 and 25. Specific weekly totals included 7.04 inches at Rock Rapids and 9.19 inches near Lester. Major flooding occurred with significant amounts of crop and pasture land inundated as the Rock River at Rock Rapids (gage site RAPI4) crested 7.8 feet above flood stage on June 22. The river fell below flood stage on June 29.

Flood in LYON, IOWA
From 21-JUN-18 09:00:00 to 28-JUN-18 10:00:00 (CST-6)
Location: ALVORD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A week of periodic heavy rainfall ending June 26 resulted in a widespread 5 to 10 inches of rainfall, much of which occurred on June 20, 24 and 25. Specific weekly totals included 7.04 inches at Rock Rapids, 9.15 inches at Rock Valley and 9.19 inches near Lester. Major flooding occurred with significant amounts of crop and pasture land inundated. The Little Rock River, a tributary which has confluence with the Rock River south of Doon, washed out a rail line sometime overnight on June 22. A train derailment occurred around 430CDT, with 33 cars leaving the track, 10 leaking an estimated 160,000 gallons of heavy crude oil into the flood waters. The city well at Rock Valley was shut down for a period following the spill.  A trailer park and several businesses were flooded as the Rock River at Rock Valley (gage site RKVI4) crested 5.3 feet above flood stage on June 22. A secondary major crest 3.5 feet above flood stage occurred on June 26. The river fell below flood stage on June 28.

Flood in SIOUX, IOWA
From 21-JUN-18 09:00:00 to 28-JUN-18 10:00:00 (CST-6)
Location: ROCK VLY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A week of periodic heavy rainfall ending June 26 resulted in a widespread 5 to 10 inches of rainfall, much of which occurred on June 20, 24 and 25. Specific weekly totals included 7.04 inches at Rock Rapids, 9.15 inches at Rock Valley and 9.19 inches near Lester. Major flooding occurred with significant amounts of crop and pasture land inundated. The Little Rock River, a tributary which has confluence with the Rock River south of Doon, washed out a rail line sometime overnight on June 22. A train derailment occurred around 430CDT, with 33 cars leaving the track, 10 leaking an estimated 160,000 gallons of heavy crude oil into the flood waters. The city well at Rock Valley was shut down for a period following the spill.  A trailer park and several businesses were flooded as the Rock River at Rock Valley (gage site RKVI4) crested 5.3 feet above flood stage on June 22. A secondary major crest 3.5 feet above flood stage occurred on June 26. The river fell below flood stage on June 28.