FLORIDA GEOLOGICAL SURVEY


This depth-profile graph was obtained from a sonic depth-recorder mov-
ing along the centerline of the channel. The water-surface elevation in
the lower reach of the river during low stages fluctuates with tide from
about 0.5 to 1.5 feet above mean sea level.
 Throughout its length the Perdido River channel is tortuous. The
low-water channel in the vicinity of Barrineau Park is about 150 feet
wide and winds through a thickly wooded flood plain that is half a mile
wide. The streambed is composed of sand and gravel and characterized
by alternate sandbars and holes.
 The steep slope of the drainage basin causes high rates of direct run-
off. Consequently, floods in this basin are usually of short duration. A rise
in water level of 15 feet is not uncommon at Barrineau Park. The highest
flood of record reached an elevation of 51.5 feet above sea level in
March 1929. The usual low-water stage is 28 feet above sea level. Dur-
ing the flood of April 1955, which was the highest in the 20-year period
ending in 1961, the river reached a peak flow of 39,000 cfs at an eleva-
tion of 49.7 feet above sea level at the Barrineau Park gaging station.
Three days after this flood peak the stage had receded 17 feet and the
river was within its banks.
 The consideration of floods and their effects on the area is an essen-
tial item in planning developments adjacent to the stream channel. The
probability of future floods can be predicted on the basis of floods that
have occurred in the past. From a study of the magnitude and frequency
of past floods, a means of estimating the frequency of floods has been
developed for Florida (Pride, 1958). Regional flood-frequency curves
applicable to this area have been developed from this report and are
presented in figure 20.
 The sustained low-flow yield of the streams should be examined in
considering an area for development. If the minimum flow of a stream
during a reasonably long period of time is known to be above the an-
ticipated demand, the supply is adequate without storage. However, if
the minimum flow falls below the anticipated demand, either of two
measures can be undertaken. Storage reservoirs can be built to store
water during periods of excess flow for use during periods of deficient
flow; or, if the deficient flow is of short duration and occurs infrequently,
the use of water might be geared to the available supply.
 The low-flow frequency curves given in figure 21 for Perdido River
at Barrineau Park, Florida, show the frequency of average flows for the
indicated periods. For example, a discharge of 250 cfs will occur as a
1-day average once in 2.4 years, or as a 30-day average once in 6.5 years.
 The Perdido River basin yields copious quantities of water. The av-