CHANNEL AND BANK STABILITY OF OSBORNE CREEK AT U.S. HIGHWAY 45 NEAR WHEELER, PRENTISS COUNTY, MISSISSIPPI by K. Van Wilson, Jr. and D. Phil Turnipseed Prepared in cooperation with the MISSISSIPPI STATE HIGHWAY DEPARTMENT Jackson, Mississippi 1989 Open-File Report 89-581 TABLE OF CONTENTS Definition of terms Abstract Introduction     Purpose and scope     General description of Osborne Creek     Channel modifications to Osborne and Twentymile Creeks     Acknowledgments Channel-bed stability     Botanical evidence of gradation     Gradation analyses Channel-bank stability     Botanical evidence of widening     Stability analyes     Widening analyses Summary References ILLUSTRATIONS 1. Map showing the location of Osborne Creek at existing U.S. Highway 45 and proposed U.S. Highway 45 relocation near Wheeler, MS 2. Graph showing estimated patterns of channel-bed gradation processes on Osborne Creek at existing U.S. Highway 45 near Wheeler, MS 3. Cross section showing critical failure surfaces for channel banks on Osborne Creek about 50 feet downstream from the proposed U.S. Highway 45 relocation near Wheeler, MS 4. Graph showing estimated patterns of channel widening on Osborne Creek at existing U.S. Highway 45 near Wheeler, MS TABLES 1. Channel-bed elevation and degradation on Osborne Creek at existing U.S. Highway 45 near Wheeler, MS 2. Dry bulk-unit weight and shear-strength properties of soil as determined on the right (south) bank of Osborne Creek, about 50 feet downstream from the proposed U.S. Highway 45 relocation near Wheeler, MS 3. Bankfull channel width and widening on Osborne Creek at existing U.S. Highway 45 near Wheeler, MS ABSTRACT The channel of Osborne Creek at existing U.S. Highway 45 near Wheeler, Mississippi, has degraded about 8 feet and widened about 33 feet since 1936. Channel degradation has totaled about 6 feet in the channel reach in the vicinity of the proposed U.S. Highway 45 relocation. Botanical evidence indicates that several bank failures downstream of the proposed relocation occurred during floods in 1983 and 1987-88. Rates of channel gradation and widening--as determined from channel descriptions and botanical evidence along the banks--were used in conjunction with soil properties to estimate probable future channel degradation and widening at the proposed relocation through the year 2010. By assuming that channel-bed elevations can be expressed as a power function with time, additional channel degradation through the year 2010 could approach 1 to 2 feet at the existing and proposed crossing of Osborne Creek. By comparison of projections of slough lines and temporary angles of stability with bankfull channel widths as a power function with time, about 10 feet of additional widening could reasonably be expected through the year 2010. 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. LizardTech's Djvu plug-in is needed to view these reports. CLICK HERE TO VIEW THE ENTIRE REPORT For questions or comments, contact K. Van Wilson.