Channel and bank stability of Twentymile Creek at U.S. Highway 45 near Wheeler, Prentiss County, Mississippi

Abstract

The channel of Twentymile Creek at existing U.S. Highway 45 near Wheeler, Mississippi, has degraded about 8 feet and widened about 73 feet since it was channelized in about 1912. No recent (at least since 1968) channel degradation or widening is evident on Twentymile Creek near the proposed U.S. Highway 45 relocation. Botanical evidence indicates that both banks in the vicinity of the proposed relocation are fairly stable, but the removal of mature riparian vegetation from channel banks could result in near-future instability. Rates of channel gradation and widening as determined from channel descriptions, discussions with local residents, and botanical evidence along the banks were used in conjunction with soil properties to estimate probable future channel degradation and widening through the year 2010. No additional channel degradation through the year 2010 is expected at the existing and proposed crossing of Twentymile Creek. At existing U.S. Highway 45, the channel width could increase about 15 feet through the year 2010; at the proposed relocation, the channel width could increase about 20 feet in the next 10 to 20 years if mature riparian vegetation is removed from the channel banks. These projections are based on the assumption that no additional channel modifications and no unusually large and destructive flooding will occur by the year 2010.

Channel and bank stability of Wolf Creek, and a tributary at U.S. Highway 45 near Wheeler, Prentiss County, Mississippi

“…The width ratios were 1.59, 1.73, 1.42, 1.41, and 1.50 for 19361.73, 1.42, 1.41, and 1.50 for ,19381.73, 1.42, 1.41, and 1.50 for , 19541.73, 1.42, 1.41, and 1.50 for , 19801.73, 1.42, 1.41, and 1.50 for , and 1988 Twentymile Creek, 15 ft of additional widening was estimated to occur by the year 2010, producing a channel width of about 113ft (Turnipseed and Wilson, 1990). Multiplying the channel width of 113 ft by 1.5, the width of Wolf Creek at existing U.S. Highway 45 is estimated to be about 170 ft by the year 2010 (23 ft wider than the 1988 width).…”