A little more than one foot of modern sediment, derived from soil erosion since the country was settled, was found by borings on the flood plain of North Tippah Creek in 1939. Resurveys in 1969 show no further appreciable sediment accumulation. There has been further deposition in some places, but about an equal amount of erosion from other parts of the flood plain.
Lack of overbank sediment accumulation since 1939 suggests that the process had practically ceased by that date. The most likely explanation is reduced flooding following channel deepening in response to 1916 dredging of Tippah Creek, to which North Tippah is tributary. Subsequent extensive changes in land use, with reduced cultivation of steeper slopes and reforestation of eroded lands, and construction of many small dams, have undoubtedly reduced the rate of sediment delivery to the valley, but apparently not until after cessation of general flood plain aggradation.
After 1939 the stream channel apparently tended to fill until straightened in 1963. Subsequently it has been enlarged by erosion of the straightened channel, and headward erosion above the straightened reach. Channel erosion may now be the principal source of sediment production.
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1 Contribution from the USDA Sedimentation Laboratory, Southern Branch, Soil and Water Conservation Research Division, Agricultural Research Service, United States Department of Agriculture, Oxford, Mississippi.
2 Geologist, USDA Sedimentation Laboratory.