Perdido River and Bay - Florida Department of Environmental ...

Water Quality Status Report: Perdido River and Bay
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Elevenmile Creek southwest to a constriction in the bay created by Grassy
and Double Points. Bayou Marcus discharges into the upper bay. The
lower limit of the middle bay is at the bay constriction created by Manuel
and Dupont Points. The main bay is bounded at the lower end by a line
from Mill Point to Inerarity Point and another line south across the Gulf
Intracoastal Waterway from Hatchet Point. Tarkiln Bayou, Soldier Creek,
and Palmetto Creek drain to the main bay. The lower bay connects the
main bay to the Gulf of Mexico through Perdido Pass and includes Bayou
St. John. This segment extends east to join the Big Lagoon at the State
Road 292 Bridge. The Big Lagoon and Intracoastal Waterway connect
Perdido Bay to Pensacola Bay. The last segment is the west bay defi ned as
the open expense of water from Hatchett Point west to the Alabama Canal.
Wolf Bay enters the west bay segment. Mobile Bay is connected to Perdido
Bay by way of Bay La Launch, Wolf Bay, and the Intracoastal Canal.
Circulation and water elevations within the bay are controlled by
wind speed, wind direction, tidal fluctuation, and freshwater discharges
from tributaries. Lowest streamflows occur during the fall and highest
streamflows occur in winter and spring. Tides are typically diurnal though
they can be semidiurnal (Grubbs and Pittman, 1997). NOAA tide tables
estimate that the tidal range is 0.5 feet, but it was observed by the USGS
during a 1994–95 water flow and loading study to have a range of 0.8 feet
(USGS Web Site). Other observers have noted that strong winds when
aligned with the north to south orientation of the bay can induce up to a
0.5 feet change in water level ([Niedoroda, 1992] as referenced in Grubbs
and Pittman, 1997).
Physiographic and Soil Features
The Perdido River and Bay Basin lays within the Western Highlands
and Gulf Coastal Lowlands physiographic provinces (Figure 2.3). The
Perdido River Basin has well-defined topographic relief with land surface
elevations in its northern portion of 300 feet or more above mean
sea level (Figure 2.4). Much of the Perdido River and its tributary
streams drain the hilly terrain of the Western Highlands. Soils that have
formed across the northern reaches of the basin originated from the Plio-
Pleistocene Citronelle Formation. This formation consists of quartz sand
with beds of clay, gravel, hardpans, fossil woods, and kaolinitic burrows
of aquatic animals. Karst topography is not evident because of the depth
of the Citronelle Formation and older impermeable clastic layers. Soils
are unconsolidated sands, silts, and clays deposited from prehistoric
seas and Appalachian deposits. Soils can be easily eroded and, coupled
with the hilly terrain, contribute to fairly severe soil erosion and stream
sedimentation problems.
The sediments within Perdido Bay are largely terrigenous clastics originating
from freshwater inflows to the bay. Finer particles have settled in
the deeper portions and more central areas of the bay resulting in accumulation
of clayey silt and silty clay sediments. Coarser sands are deposited
closer to the shoreline. Sediment grain size generally increases moving
seaward (Schropp et al., 1991).