Drainage Map of the Mississippi River and its Tributaries. Some Facts and Figures

QUESTIONS! QUESTIONS!
For Jack, who wants to know more about all the tributaries of the Mississippi River: how many there are,  their names, and how long they are!

NPS.gov watershed tributaries

There are some 250 tributaries of the Mississippi which drain a total area of more than 1,247,000 square miles–one third of the nation’s landmass–extending from the Allegheny Mountains in the east to the Rocky Mountains in the west!

Remember the Mississippi River Flood of 1993? It wasn’t just the Mississippi River flooding that wreaked havoc, it was that all those tributaries flooded as well! At one point, the volume of water flowing past St. Louis was eleven times the volume of Niagara Falls!!

We start here with quick facts on the Mississippi River and several navigable tributaries! Please follow links for a little more depth of historical interest and to see our collection of hand-painted maps!

The Mississippi River, from its source at Lake Itasca in Minnesota, to the Gulf of Mexico, is approximately 2,348 miles long. The combined reach of the Missouri-Mississippi Rivers is 3,741 miles–a length exceeded only by the Amazon and Nile rivers. The Mississippi River has shortened by several hundred miles since the days of Mark Twain. Even today it varies 30-50 miles each year.

The widest navigable part of the Mississippi is Lake Pepin, on the Upper Mississippi, where it is approximately 2 miles wide. The average current flows from 1.2 miles per hour nearer Lake Itasca, and about 3 mi per hour nearer New Orleans.

Our Mississippi River Ribbon Map has been a best-selling Gift for many years. Lisa now offers her own custom ribbon map designs of both the OHIO RIVER and the Missouri River. Please click on any map image for more info on the map or the tributary. Or PHONE 888-255-7726 to order any map. Mention you saw it on greatriver.com for a one time 10% discount!   Click on map images for more info on the tributaries.

 

 

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DAILY U.S.G.S. FLOOD ALERT MAP

arrow-clip-art-Arrow-clip-art-16CURRENT RIVER FLOOD ALERTS

Below is the USGS interactive map that provides REAL TIME info on which Rivers in the US are cresting. The map below is accurate every day. Black Triangles indicate flood stage. Looking to compare stats with the Flood of 1993? CLICK HERE.

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See more interactive maps by clicking the category in the list to right: INTERACTIVE MAPS

Official Flood Stats from August 2007 Rains in Minn/Wis

I recently ran across a number of stats presented by area scientists regarding the massive rains along the Upper Mississippi River last August. These rains produced unprecedented landslides in bluff country that resulted in seven deaths and several homes on both sides of the river sliding down onto the roads.

For more detailed stories, stats, photos, and reports from the August 07 flooding and landslides, see http://www.greatriver.com/natural/disaster/August07.htm

Official FLOOD STATS

15.1 inches of rain fell in Hokah, Minn., over a 24 hour period on August 19. The previous high was 10.84 inches set in 1972.

The Root River crested at 18 feet in Houston, Minn.  When compared with previous flooding events, the August ’07 floods had up to 5 times more rainfall.

Scientists report that the flood was so rare, the probability of its existence was once in 500 years, perhaps even once in 1,000 years. The storm’s wrath was comparable to a Category 5 hurricane.

Interestingly enough, the invertebrate count in large streams fell from about 4,000 per square meter to just 1000 after the flood. A specific amphipod, a staple of trout diets, dropped from about 250 per square meter to less than 10.

23.6 inches fell during the month of August, 9.5 inches shy of the average ANNUAL precipitation.

For more on the dangers posed by landslides on the 600 ft high bluffs along the Minnesota and Wisconsin border see our feature from Fountain City, Wis., When Bluffs Throw Boulders.  On April 5, 1901 a single boulder fell from the bluff face to smash a home and kill its occupant. Some 85 years later it happened again… in the same spot. This time, the Rock was left in place and is open to the public for viewing at the Rock in the House attraction on Hwy 35.

GEOLOGY 101… WHY Land Slides Happen along the Mississippi River Bluffs

    The bluffs of the “Driftless” region that stretches along the Mississippi River are formed of limestone bedrock covered by an ancient mix of clay and river silt. Under most conditions this is provides a solid base for home building, though most counties restrict building to a slope of 20-30%.  Homes that are built on “benches” may have much steeper areas above them (or below). Between 1998 and 2006, 205 homes and 10 condominiums were built in La Crosse County on slopes with between 20% and 30% slopes.

Historically heavy rain during the night of August 19, 2007, meant that water drained from the tops of the bluff to flow into the valleys. Water flowing over the rock faces probably fell like fabulous waterfalls (though I haven’t run across anyone who can claim to have seen it). This completely saturated the clay and silt which cover the bluffs.

According to a La Crosse Tribune story, as water particles fill the space between silt particles the silt and clay firstbecome “plastic” and then “viscous.” When “plastic” it will move when pressure is applied to it (such as the weight of a home). When “viscous” it begins to flow under its own weight… like a glacier, only much more quickly. This flow is what caused the collapse that is so visible in the bare canyons, and the mud and rubble along the base of the bluffs throughout the coulee region.

The soils may have been more vulnerable because the area was so dry, and the water fall so far beyond the historic record. The fact that residents remove the thick canopy of deep rooted trees and brush to plant grass may also have made the bluff sides more vulnerable, according to La Crosse County.

Aftermath?

Certainly many counties will be reconsidering restrictions on developing bluff side slopes. Onalaska currently restricts building on slopes of more than 20%, Holmen restricts building on slopes over 12%, La Crosse 30%, town of Bergen restricts development at 20% but does allow building on “benches.” Winona currently restricts building on slopes greater than 15%.

Many researchers point to increasingly severe droughts, rain and heat as the by-product of global warming. So can we expect more such rains? The experts do think so.

More!

Chronology of the Rains in August 2007

When Boulders Roll … Landslides on the River

The Floods of 1993 and 1996

Return to the Mississippi River Home Page at www.greatriver.com