Early reports starting on the 9th are in this entry, with several later reports starting on the 13th in Part II.
Additionally the combination of heavy snowpack and heavy rainfall absorbed into the snow partially collapsed a horse barn roof in rural Adair County near Greenfield.
An ice jam occurred in Ottumwa on the Des Moines River causing flash flooding were water rapidly rose several feet on the morning of the 12th. Several cars and campers were flooded.
A relatively deep and widespread snowpack existed across the region during early to mid March. Many areas in central and northern Iowa had around a foot to two feet of snow on the ground, along with many areas in upstream river basins in Minnesota and the Dakotas having similar or deeper snowpacks on the ground. Additionally, with the below normal temperatures throughout the majority of the 2019 year to date, soils were frozen to depths of a foot or more throughout the aforementioned areas. All of that primed the area for potential moderate to major flooding issues should a rapid snowmelt and/or rainfall event occur, which unfortunately came to fruition.
The primary driver was two-fold with warm air advection on the backside of a departing high pressure on the 12th, and a sizable low pressure system that moved through the region on the 13th and 14th. The event began with widespread temperatures and dew points in the upper 30s to low 40s on the 12th with the initial warm air advection, which continued through the overnight hours into the 13th. As the low pressure system developed off the Colorado Rockies, warm air advection continued to push temperatures and dew points up into the upper 40s and low 50s on the 13th and 14th, aiding the rapid snow melt. On top of the rapid snowmelt, which often went from 12 or more inches on the ground to zero in a matter of about two days, light to moderate rainfall occurred ahead of and on the backside of the low pressure system on the 13th and 14th. All combined to cause widespread overland flooding, river flooding, and ice jam issues.

Flood in MAHASKA, IOWA
From 09-MAR-19 20:55:00 to 10-MAR-19 15:30:00 (CST-6)
Location: EVANS
Flood cause: Heavy Rain / Snow Melt
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Flooding was observed around the Muchakinock Creek west of Oskaloosa. Water was reported over State Highway 92.

Flood in CLARKE, IOWA
From 12-MAR-19 13:21:00 to 15-MAR-19 09:00:00 (CST-6)
Location: HOPEVILLE
Flood cause: Heavy Rain / Snow Melt
Property damage: 200.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Localized flooding was reported in low lying areas of Murray. West of Osceola, 190th Avenue was closed due to ponding of water over the road. As the rain and snowmelt continued, numerous roads across the county began to flood and were closed as well.

Heavy Rain in ADAIR, IOWA
From 09-MAR-19 14:00:00 to 09-MAR-19 14:00:00 (CST-6)
Location: GREENFIELD
Property damage: 40.00K
Crop damage: 0.00K
Reported by: Broadcast Media

A heated horse barn near the town of Greenfield experienced a partial roof collapse due to the snow and rainfall absorbed into the snow putting too much weight on the that part of the roof. Minor injuries to a couple of horses were reported.

Flash Flood in WAPELLO, IOWA
From 12-MAR-19 09:00:00 to 12-MAR-19 14:00:00 (CST-6)
Location: OTTUMWA
Flood cause: Ice Jam
Property damage: 300.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Flash flooding occurred on the north side of Ottumwa due to an ice jam on the Des Moines River. Water rapidly rose several feet flooding a campground and a few local residences. Some cars and campers were flooded.