FLORIDA GEOLOGICAL SURVEY


square mile. The average unit runoff from gaged tributaries in Florida
(Pine Barren Creek and Moore Creek) is 2.1 cfs per square mile.
 The lower part of the Escambia River exerts a major influence on
the two-county area, not only because it serves as a source of water sup-
ply but also because of its size and location with respect to the fast de-
veloping industrial area around Pensacola. The lower basin is about 9
miles wide. The river channel is tortuous and winds through a low,
swampy flood plain about 3 miles wide. Several estuarine channels ex-
tend into the flood plain from Escambia Bay. Farther upstream two
islands within the flood plain are exposed during periods of low river
stages.
 Flow in the lower river basin is affected by tide to a point north of
Brosnaham Island. The change in stage due to tide effect at the north
end of the island was 1.8 feet during a series of flow measurements
made on August 24, 1954, but the direction of flow does not reverse at
that point. A tide range of 2.5 feet is not uncommon near the nylon plant
of the Chemstrand Corporation. An observation of flow conditions made
near the Chemstrand plant on October 22, 1952, showed the flow to re-
verse at that point.
 Soundings along the centerline of the lower channel, made by use of
 a sonic depth-recorder, showed the deepest part of the channel to be
 about 50 feet at a point 5 miles upstream from Escambia Bay. A depth-
 profile graph made from these soundings is given in figure 23. Deep
 holes in the channel, such as that 5 miles upstream from the river mouth,
 trap salt water that can be a source of contamination of surrounding
 ground-water supplies if heavy pumping from wells near the river is
 carried on for long periods of time.
 The tributaries below Pine Barren Creek are short and drain small
 areas. The ridges forming the drainage divides vary in elevation from
 150 to 200 feet above sea level. The Escambia River flood plain slopes
 from about 15 feet above sea level near the mouth of Pine Barren Creek
 to sea level at Escambia Bay.
 The larger streams in the Escambia River basin with watersheds in
 Florida are Pine Barren Creek, Canoe Creek, and Moore Creek.
 Pine Barren Creek drains an area of 98.1 square miles, 85 square
 miles of which is in Escambia County, Florida. The headwaters of the
 creek are near the town of Atmore, Alabama, 2 miles north of the state
 line. The average yield of Pine Barren Creek is 28.6 inches per year,
 which is about 45 percent of the rainfall on the basin. A very substantial
 base flow of 60 cfs (38.8 mgd) has been measured from the area of
 75.3 square miles above the gaging station. The magnitude of flow will