So even with the increase in moisture in the atmosphere of 6% and an increase in rains(mostly beneficial) and also a slight increase in flooding, one of the few detrimental effects of climate change(slight uptick in flooding- slight increase in planting delays) it's  NOT resulting in any sort of flooding crisis that is challenging records of past flooding.

US Rainfall Records

edit: May 7, 2019-cleaned up the list at the bottom to be more legible

The map/link below shows rainfall records for the US for total rains, going from a time frame of 1 minute up to a time frame of 1 year. If you go to the link, you will see this better. It shows the date of occurrence for each of these 20 events. The surprise is that all of them occurred BEFORE 1983 and before man made global warming and climate change would have been a factor. I can't completely explain this as I had recently done a study on our local region going back 120 years that did show heavier rain events over the last 30 years with an especially big increase in the last 15 years..

I think that we have in fact had at least a slight increase in the # of extreme rain events, however, this shows that regardless of humans the really extreme events have always happened and will continue to happen.

http://www.nws.noaa.gov/oh/hdsc/record_precip/record_precip_us.html

Duration  Amount (in)  Location  Start date

1-min 1.23 Unionville, MD 4  Jul 1956

5-min 2.03 Alamogordo Creek, NM  5 Jun 1960  

12-min 2.30 Embarrass, WI 28 May 1881  

15-min 3.95  Galveston, TX 4 Jun 1871

30-min 7.00 Cambridge, OH  16 Jul 1914    42-min 12.0  Holt, MO  22 Jun 1947

 13.8*  Burnsville 6 WNW, WV  4 Aug 1943

60-min 12.0 Holt, MO  22 Jun 1947  

 12.0 305 Kilauea Sugar Plantation, Kauai, HI  24 Jan 1956  

90-min 14.6 Burnsville 6 WNW, WV 4 Aug 1943  

2-hr 15.0  Woodward Ranch (D'Hanis), TX  31 May 1935  

2.17-hr 19.0 Rockport, WV  18 Jul 1889  

2.75-hr 22.0  Woodward Ranch (D'Hanis), TX  31 May 1935  

3-hr 28.5  Smethport, PA  18 Jul 1942  

4.5-hr 30.7  Smethport, PA  18 Jul 1942  

12-hr 34.3  Smethport, PA 17 Jul 1942  

18-hr 36.4 Thrall, TX  9 Sep 1921  

24-hr 43.0  Alvin, TX 29.42 -95.24 25 Jul 1979

3,4,5 4-day 62.0  Kukaiau, Hamakua, HI  27 Feb 1902  

8-day 82.0  Kukaiau, Hamakua, HI  28 Feb 1902  

1-month 149  Mt. Waialeale, Kauai, HI  1 Mar 1982  

12-month 739  Kukui, Maui, HI  1 Dec 1981

Updated Sept. 2020

2018  was the 3rd wettest year on record in the US and you'll note that the area on the map below in light purple shade across N. IA was THE wettest year ever in 2018, so soils have been saturated and rivers high in that area. :

Wettest Years  

                  https://www.ncdc.noaa.gov/sotc/national/201813/supplemental/page-6/

Total Precipitation

https://en.wikipedia.org/wiki/Mississippi_River_floods#Flood_of_1788

Worst flooding in USA history, looking at all rivers--1927

Worst flooding for the lower Mississippi River.

1. 1927

2. 1973

3. 1937

4. 2011

Worst flooding for the Upper Mississippi River using actual discharge/levels

1. 1844

2. 1993

So although recent rains have been excessive and the most in over 2 decades for the Midwest and rains  HAVE increased from climate change and an atmosphere that can hold 6% more moisture, we have not exceeded records in the past.........other than at isolated locations, which is not unusual for extreme weather events.

I decided to look back on records to see when the greatest flooding on the Mississippi occurred. Turns out that the worst flooding in this countries history occurred  93 years ago (glad that the internet gives us access to weather records).

https://www.weather.gov/media/jan/JAN/Hydro/Flood_History_MS.pdf

"The Great Mississippi Flood of 1927 was the most destructive flood in United States history.  This flood extended across Illinois, Indiana, Missouri, Kentucky, Texas, Oklahoma, Kansas, Tennessee, Arkansas, Mississippi, and Louisiana.  At one point the river was approximately 80 miles wide near Vicksburg, MS.  The flooding was a result of persistent heavy rainfall across the Central U.S. starting in August 1926 and continuing through the spring of 1927. As unprecedented amounts of run-off from the different tributaries combined, extreme water levels churned by wind overwhelmed the levees protecting the Mississippi Valley floodplains, breaching the flood defenses as the water traveled southward. It was not until August 1927 that the last of the floodwaters had flowed into the Gulf of Mexico.For Mississippi, the most significant flooding"

This is the link that goes back the farthest with regards to flooding on the lower Mississippi:

The worst flooding, by far was in 1927,  followed by 1973, then 1937.

https://www.weather.gov/lix/ms_flood_history

Here a good link with information regarding flooding along the entire Mississippi  River. 

Mississippi River floods

https://en.wikipedia.org/wiki/Mississippi_River_floods

Great Mississippi and Missouri Rivers Flood of 1993

Main article: Great Mississippi and Missouri Rivers Flood of 1993

The flood occurred on the Mississippi and Missouri rivers and their tributaries between April to October 1993. The flooded area totaled around 30,000  square miles (80,000 km²)^[14] and was the worst since the Great Mississippi Flood of 1927 as measured by duration, square miles inundated, persons displaced, crop and property damage and number of record river levels.

++++++++++++++++++++++++++++

However, on further review, we DID find a worse flood than 1993 on the Upper Mississippi:

https://en.wikipedia.org/wiki/Mississippi_River_floods#Flood_of_1788

Great Flood of 1844

Main article: Great Flood of 1844

The largest flood ever recorded on the Missouri River and Upper Mississippi River in terms of discharge.  The adjusted economic impact was not as great as subsequent floods because of the small population in the region at the time.This flood was particularly devastating since the region had few if any levees at the time.  Among the hardest hit were the Wyandot who lost 100 people in the diseases that occurred after the flood.  The flood also is the highest recorded for the Mississippi River at St. Louis.  After the flood, Congress in 1849 passed the Swamp Act providing land grants to build stronger levees

Extreme precipitation events have always occurred, but are they changing?

https://wattsupwiththat.com/2020/09/07/extreme-precipitation-events-have-always-occurred-but-are-they-changing/

Worst floods in World History/US +rain records
https://www.marketforum.com/forum/topic/29362/

From a meteorological point of view, if we increase the amount of moisture in the warmer atmosphere(in this case by something like 6% but that varies-more in the higher latitudes) we WILL get more precipitation.
 
That includes high end, excessive rain/flooding events.  To deny this, is to deny the physical laws and reality.

With regards to more extreme events, that's not always the case. The warming has been greatest in the higher latitudes(coldest places warming the most, especially during the coldest times of year). Nights are warming more than days.

This has decreased the meridional temperature gradient. As a result there is less energy available for mid latitude cyclones/weaker jet streams and there has been a significant decrease in violent tornadoes.
Also, less extreme cold days.

But more extreme rain and extreme heat days from climate change.

Cold kills 16 times more humans than heat and cold kills hundreds of times more non human life than heat.

So life prefers it this way................the beneficial warming(with the heavier rains).......... otherwise known as a climate optimum using authentic scientific (not political) verbiage.