Ferrell’s Bridge Reservoir is located in the northwestern part of the
Gulf Coastal Plain (Fenneman, 1938: 109-110), which is characterized
topographically by rounded hills sculptured from the superficial clays
and sands of the region. The subsoil—a sandy clay in various shades of
yellow, orange, and red—is capped by a thin mantle of gray sand which
evidently derived by differential erosion from the sandy clay. The
exposed geological formations recognized in the general region are clays
and sands of the Eocene Claiborne group (Sellards _et al._, 1958:
606-666).
The reservoir is situated in the Austroriparian Biotic Province (Blair,
1950: 93-117). The uplands are thickly timbered, principally with pines,
while the stream valleys sustain heavy stands of mixed hardwoods (oaks,
cypress, gum, walnut, hickory, holly, and others) in addition to some
pines. All the virgin forests were completely timbered out years ago.
Bear and panther, which were formerly common, have long since
disappeared from the area, but a large population of deer, raccoon,
opossum, fox, rabbit, beaver, and other small mammals survives to the
present day. The streams abound with several varieties of fish.
The climate is relatively humid, the annual rainfall at the Gilmer
station averaging 43.5 inches (U.S. Dept. of Commerce, _Climatological
Data, Texas_, V. 63, No. 13: 361). The mean annual temperature for
Upshur County is 65 degrees (_Ibid._: 357).