Running Water - The Changing Earth: Exploring Geology and Evolution - page 315

Geo-inSight The Flood of '93

Although several floods take place each year that cause
damage, injuries, and fatalities, the last truly vast river
flooding in North America occurred during June and July
of 1993. Now called the Flood of ‚ 93, it was responsible for
50 deaths and 70,000 were left homeless. Extensive
property damage occured in several states, but particularly
hard hit were Missouri and Iowa (see chart). Unusual
behavior of the jet stream and the convergence of air
masses over the Midwest were responsible for numerous
thunderstorms that caused the flooding.

Convergence zone of
recurrent
thunderstorms

Cool, dry
air

Area of
flooding streams

WA

ME

MT ND

VT

1. The dominant weather pattern for
June and July 1993. The jet stream
remained over the Midwest during
the summer rather than shifting
north over Canada as it usually
does. Thunderstorms developed in
the convergence zone where warm,
moist air, and cool, dry air met.

MN NH

OR

MA

NY

ID

SD WI

CT

MI

RI

WY

PA

NJ

IA

NE

OH MD

DE

NV

o

IN

IL

UT

WV

CO VA

CA KS

MO

KY
TN

NC

OK

SC

AZ

AR

NM

GA

AL

AK

TX LA

FL

Wa r m, mois t air

Illinois
River

Mississippi
River

x

2. Satellite images of the Mississippi,
Missouri, and Illinois rivers near the juncture
of three rivers during the drought of 1988
(left), and during the flood of 1993 (below).
The "x" marks the site of Portage des Sioux,
Missouri (see facing page).

Missouri
River

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