REPORT OF INVESTIGATIONS No. 40


be different at any other point in the basin. Based on a flow measure-
ment of a tributary entering just below the gaging station, it is assumed
that the magnitude of flow at any point in the basin is proportional to
the size of the area drained above that point.
 The average flow from the Pine Barren Creek basin is estimated to
be 207 cfs, of which about 28 cfs comes from Alabama and 179 cfs from
the drainage area within Escambia County, Florida. About two-thirds of
the total streamflow is base flow or seepage, and one-third is direct run-
off from overland flow.


Su.r m.d. by d~plh
ncordr Au9.22,1961


-250- Chloride t ont oA. 2219
--250-- Chloride oltean!. in parts per inmocl


 Figure 23. Channel-bottom profile for lower Escambia River.

 The length of the Perdido River basin is about six times the width.
This elongated shape and the steep topography of the basin produce a
short time of concentration of runoff. Rain anywhere on the basin has to-
move only a short distance before reaching the main channel. The steep.
valley slope of the main channel allows this water to flow at high veloci-
ties to the Escambia River. The channel-bottom profile of Pine Barren
Creek is given in figure 24. This channel has an average slope of more
than 10 feet per mile.
 The fast-changing rates of flow during floods in this basin can be
visualized more clearly by comparing an average flow for a day with the
momentary peak flow. The mean daily flow for April 14, 1955, was 9,46(0