- Droughts are long
periods (over one year) of below-average precipitation. The most recent
drought to affect the Northern Plains was during the years 1988-1989.
The most notorious drought was the Dust Bo wl, affecting much of the middle
of North America during the mid 1930's. One way to quantify the magnitude
of drought is the Palmer
Drought Severity Index (PDSI). A PDSI near zero indicates moisture
conditions are near climatological averages, while negative values mean
drier than average conditions exist over a region, and positive values
signify wetter than average conditions.
- Floods can occur
anywhere. On average in the U.S. each year, nearly 75,000 people are evacuated
from their homes and more than $250 million in property damage occurs
(Federal Emergency Management Agency statistics). I n the Grand Forks
1997 flood, over 60,000 people were evacuated and property damage could
exceed $2 billion.
floods in the region and around the world
Forks 1997 flood
flood of 1993 on the Mississippi and Missouri Rivers
floods in 1996
- Flash floods have
occurred in many areas of the U.S. They can arise with little or no warning
and have the potential for massive destruction.
City, South Dakota, flash flood of 1972
Creek, Colorado, flash flood of 1996