Moisture content, bulk density, and organic content of surficial
sediments were estimated with a penetrometer in Navigation Pools
4 and 8 of the Upper Mississippi River during 1994 and 1995.
Mean moisture content of sediment was low in both Pool 4 (39%, SD
= 15.0%) and Pool 8 (34%, SD = 13.7%), suggesting that soft, fine
sediments are uncommon in these pools. Sediment in much of the
off-channel habitat was found to have similarly low moisture
content. Sediment in small backwaters was particularly low in
moisture content, although areas with sediment moisture content
greater than 70% were found in small backwaters. Sediment in the
large backwaters of Pool 4 was similar to sediment in the small
backwaters of Pools 4 and 8, while in Pool 8 the large backwaters
areas had sediment with a higher mean moisture content of 57% (SD
= 14.8%). Only deep, dredged areas in Pool 8 were dominated by
sediment with a high moisture content; here the mean moisture
content was 67% (SD = 21.1%). The large, open water off-channel
area in lower Pool 8 formed by impoundment had sediments similar
to those of channel habitats. As a whole, sediment in
off-channel habitats in Pools 4 and 8 had low moisture content,
which suggests either small inputs of fine sediment or efficient
transport of fine sediment through the off-channel habitats.
