FLOOD03485

• County: Denver
• Community: All
• Stream Name: All
• Basin: South Platte
• Title: Comparison of Estimated Flood Peaks with Historic Floods
• Date: 1/1/1986
• Prepared For: State of Colorado
• Prepared By: USDOI
• Floodplain - Doc Type: Educational/Technical/Reference Information

The values in table 21 compare favorabl\ with the reponed storm tolal In the Immediate area of
10 to 12 inches in about 4 h,

Tab'f;; :: 1 - BcSI.l averaged PMF' tor Dark Gulcn and
North Fort, TriDLJTaneS to BIg Thompson River, CO.

Duration, Depth,
h In
1 122
6 19.3
24 28,3
72 35,0

Based on the above assumptions and data, PMF hydrographs were prepared for both basins, The
Dark Gulch Basin PMF peak is 12,900 ft3!s and the North Fork tributary PMF peak is 16,100
ft3!s. These figures result in percentage estimates of 56 percent and 60 percent, respectively,
for the recorded flood peak discharges in this disastrous 1976 Colorado event. Plates 29 and 30
show a comparison of the computed PMF hydro9raph peaks with the historic flood peaks for
these two small basins.

27. Tye River near Norwood, Virginia

At the time of its occurrence in August 1969, Hurricane Camille, was the most intense hurricane
of record ever to have entered the U.s. mainland. As it passed over central Virginia on the night
of August 19 and on the morning of August 20, recordbreaking flooding occurred. The floods,
rain-induced landslides, property damage, and deaths that resulted make this hurricane event the
worst natural disaster ever to strike Virginia, Flows on the Tye River and the Upper James River
are still the highest ever recorded, even larger than the flooding later produced by Hurricane Agnes
in 1972 [46]

,

1
l'
"
r'

On the evening of August 19, Camille intensified rapidly as she passed eastward over the Ap-
palachian Mountain ridge, By late in the night of August 19, the hurricane had merged with heavy
showers and thunderstorms already in the mountains. This merger resulted in a very intense band
of rain approximately 50 mi wide, which extended from White Sulphur Springs, West Virginia, to
Fredericksburg, Virginia, In Nelson County, spot measurements of as much as 27 to 28 in of rainfall
in 8 h were reported. These amounts were more than triple the previous record Virginia rainfall
of 8A inches in 12 h during a 1942 hurricane.

Record floods occurred along streams in Camille's path, Many had recurrence intervals much
greater than the established 50-yr floods, and some had return periods in excess of 100 yr, The
flood at station 02028000, Tye River near Norwood, Virginia, with a stage of 41 ft and a maximum
discharge of 200,000 ft3!s from 360 mi', had a discharge 5 Y2 times the 50-yr flood estimated
from data at the gauge, It far exceeded the stream's previous record floods of 33,500 ft3!S
recorded in 1942, and again in 1944, Two stations on the James River reported peaks of 1.2

59