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CHAPTER IV: WILDLIFE HABITATS FOR MISSISSIPPI’S SGCN,

THREATS AND CONSSERVATION ACTIONS^194

flood plains. Dams have been placed on numerous streams for flood control, water supply for
municipalities and industry, navigation and recreation. These dams restrict movement of animals and
alter hydrologic characteristics of the rivers on which they are built. The major tributaries of the upper
Yazoo River (Coldwater, Tallahatchie, Yocona and Yalobusha) have flood control dams. The Pearl
River system is now divided by Ross Barnett Dam which effectively restricts passage of fishes upstream
from the dam. Construction of the Tennessee-Tombigbee Waterway created an unnatural connection
between two separate drainages and altered the Tombigbee drainage. The Tombigbee River is now a
series of navigation pools impounded by multiple locks and dams, which bears little resemblance to the
original Tombigbee River. The only portion of the Tennessee River which borders Mississippi in the
northeast corner, is impounded by Pickwick Dam. Numerous smaller weirs and lowhead dams exist on
streams throughout the state.

Land use practices in forestry and agriculture have resulted in vast increases in sediment deposition in
streams as well as increasing erosion. Headcutting, which can be caused by stream channel alteration,
has resulted in long stretches of stream erosion and bank destabilization which move progressively
upstream. Many streams throughout the state show the effects of headcutting. Most of these streams
have broad, shallow channels with unstable substrate and little or no canopy cover. Drainage of
wetlands and removal of groundwater for irrigation has caused a decrease in the water table in some
areas, especially in the Delta region. This has caused extremely low flows in streams during dry
periods. Streams have been receptacles for sewage, industrial waste and agricultural runoff. The
Mississippi Department of Environmental Quality (2004) lists many factors which affect water quality in
streams, including organic enrichment, pesticide contamination, sedimentation and siltation, mercury
contamination and pathogens.

12.1 Mississippi River

„ Value to SGCN - 46

„ Rank - 11th of 18 Lotic and Lentic Systems

DESCRIPTION AND LOCATION
MSRAP
The Mississippi River is the largest river in the United States,
draining about one-third of the land mass in the lower 48
states. The upstream drainage area of the Mississippi at
Natchez is over 1,200,000 square miles. The Mississippi
River as it borders Mississippi is a large, deep river with primarily sand or sand and gravel substrate.
There are often large sand bars in the river bends. Many alterations have been made on the river,
including cutting off of bendways to shorten the channel, and extensive channel stabilization with rip
rap, articulated concrete mattress (ACM), wing dams and dikes. Channels have also been dredged, and