U.S. Floods of 1981
By C.A. Perry, B.N. Aldridge, and H.C. Ross of the USGS
The first significant flood of 1981 was a result of rain falling on
deep snow in the area from New Hampshire to eastern Pennsylvania. Rainfall
of 1 to 4 in. occurred over the area and, along with temperatures in the
50- to 60-°F range, caused 6 to 12 in. of snow to melt. Ice jams were the
major factor causing the flooding. The highest recorded stage (26.6 ft) on
the Delaware River at Matamoras, Pennsylvania, was a result of a massive
Considerable spring flooding occurred in Montana during May when four
extensive storms created conditions that resulted in flooding in the
Helena and Continental Divide areas. Flooding occurred when excessive
precipitation combined with snowmelt. At 13 streamflow-gaging stations,
recurrence intervals of greater than 100 years were recorded. Near
Boulder, Montana, the maximum discharge of the Boulder River was twice the
previous maximum of record. These floods were some of the costliest in
Montana's history, with total damages exceeding $30 million (Paulson and
A deadly flash flood struck Austin, Texas, during the night of May 24.
A short, intense rainfall produced as much as 10 in. of rain in 4 hours.
Streams rose rapidly, beginning about 10:00 p.m. and peaking about
midnight. The floods receded just as quickly, so most streams were at
preflood levels by 3:00 a.m. The flood resulted in 13 deaths and $40
million in damages. The speed at which the streams rose to flood levels
contributed to the number of deaths as the floods probably caught many
people unaware of the danger.
The summer months were plagued with floods in the North-Central States.
Illinois and Indiana were the hardest hit, as rains began in May and
continued through July. Flooding was widespread from Wisconsin to
Kentucky, with the most severe floods in scattered areas. Thirteen
counties dispersed over Illinois, Ohio, and western Pennsylvania were
declared Federal disaster areas because of flooding in mid-June.
Agriculture in Illinois and Indiana suffered substantially from the storms
and resulting floods.
On August 29, a tropical depression moved inland at Brownsville, Texas,
and continued to move up the Rio Grande Valley. By August 30, the
depression reached San Antonio and, during the evening, created a line of
thunderstorms that produced 8 to 12 in. of rain in the area. Water levels
on many rivers in the region were near record highs.
October brought excessive rains and flooding to Texas and Oklahoma. On
October 5, rainfall amounts totaling 8 in. caused severe urban flooding in
Houston. A storm produced 11 in. of rain in southern Texas on October 6
through 7. Record floods were produced in Oklahoma and Texas from a storm
that lasted from October 11 to 16. In a 3-day period from October 11 to
14, 17 to 20 in. of rain fell in south-central Oklahoma and north-central
Texas. As a result, floods that exceeded the 100-year recurrence interval
occurred in central Texas. The damage totals exceeded $115 million in
Texas and Oklahoma combined.