GEOMORPHIC RESPONSE TO CHANNEL MODIFICATIONS OF SKUNA RIVER AT THE STATE HIGHWAY 9 CROSSING AT BRUCE, CALHOUN COUNTY, MISSISSIPPI by K. Van Wilson, Jr. and D. Phil Turnipseed U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 94-4000 Prepared in cooperation with the MISSISSIPPI DEPARTMENT OF TRANSPORTATION Jackson, Mississippi 1994 DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Robert M. Hirsch, Acting Director For additional information Copies of this report can be write to: purchased from: District Chief U.S. Geological Survey U.S. Geological Survey Earth Science Information Center 100 W. Capitol St., Suite 710 Open-File Reports Section Jackson, Mississippi 39269 Box 25286, MS 517, Federal Center Denver, Colorado 80225 CONTENTS Page Abstract..................................................................................................................... 1 Introduction ........................................................................................................... 2 Background.................................................................................................. 2 Purpose and scope...................................................................................... 4 Approach...................................................................................................... 4 General description of Skuna River......................................................... 4 Channel-bed material properties.................................................. 5 Channel-bank material properties................................................ 5 Channel modifications of Skuna River.................................................... 5 Acknowledgments...................................................................................... 7 Geomorphic response to channel modifications................................................ 7 Cross sectional evidence............................................................................ 7 Botanical evidence...................................................................................... 8 Channel-bed elevation............................................................................... 11 Channel shape............................................................................................. 20 Channel pattern........................................................................................... 29 Bankfull discharge...................................................................................... 29 Channel slope.............................................................................................. 33 Bankfull stream power............................................................................... 34 Channel-bank stability............................................................................... 34 Summary and conclusions..................................................................................... 41 References................................................................................................................ 42 ILLUSTRATIONS Figure 1. Map showing location of Skuna River at State Highway 9 at Bruce, Mississippi........................................................................... 3 Figures 2-4. Graphs showing: 2. Channel cross sections at the State Highway 9 bridges crossing Old Skuna River, Skuna River Canal, and Skuna River Canal tributary at Bruce, Mississippi.................... 9 3. Channel-bed elevation for Skuna River Canal at Federal Aid Secondary Route 794, State Highway 9, and State Highway 341.................................................................................... 15 4. Annual minimum daily stage and minimum bed elevation for Skuna River Canal at State Highway 9 at Bruce, Mississippi....................................................................................... 16 in ILLUSTRATIONS-Continued Page Figures 5-8. Graphs showing: 5. Annual minimum daily stage and discharge for Skuna River Canal at State Highway 9 at Bruce, Mississippi......................... 18 6. Estimated patterns of channel-bed degradation on Skuna River Canal at State Highway 9 at Bruce, Mississippi............... 19 7. Estimated patterns of channel deepening on Skuna River Canal at State Highway 9 at Bruce, Mississippi......................... 21 8. Estimated patterns of channel-widening on Skuna River Canal at State Highway 9 at Bruce, Mississippi......................... 22 9. Photographs showing old car bodies on the upstream left (south) bank of Skuna River Canal at State Highway 9 at Bruce, Mississippi........................................................................... 24 10. Graph showing bankfull channel width divided by channel depth for Skuna River Canal at State Highway 9 at Bruce, Mississippi........................................................................... 25 11. Photographs showing views upstream and downstream of the State Highway 9 crossing of Skuna River Canal at Bruce, Mississippi, February 20,1992.......................................... 28 12. Map showing historical changes in channel pattern of Skuna River Canal in the vicinity of State Highway 9 at Bruce, Mississippi....................................................................................... 30 Figures 13-16. Graphs showing: 13. Bankfull discharge from annual stage-discharge relations for Skuna River Canal at State Highway 9 at Bruce, Mississippi....................................................................................... 31 14. Annual peak stage and discharge for Skuna River at State Highway 9 at Bruce, Mississippi.................................................. 32 15. Average channel slope of Skuna River Canal between State Highway 341 and Federal Aid Secondary Route 794............... 35 16. Bankfull stream power for Skuna River Canal at State Highway 9 at Bruce, Mississippi.................................................. 36 IV ILLUSTRATIONS-Continued Page 17. Cross sections showing critical failure surfaces for saturated channel banks on Skuna River Canal in the vicinity of State Highway 9 at Bruce, Mississippi, 1989............................... 39 18. Cross section showing critical failure surfaces for saturated channel banks on Old Skuna River about 130 feet upstream from State Highway 9 at Bruce, Mississippi, 1989................................................................................................... 40 TABLES Table 1. Bulk-unit weight and shear-strength properties of channel- bank material from borehole tests in 1989 on the left (south) banks of Skuna River Canal and Old Skuna River about 70 and 100 feet, respectively, upstream from State Highway 9 at Bruce, Mississippi.................................................. 6 2. Botanical and geomorphic evidence of channel-bed degradation collected in 1989 on Old Skuna River and Skuna River Canal tributary in the vicinity of State Highway 9 at Bruce, Mississippi.................................................. 10 3. Botanical and geomorphic evidence of channel-bank widening collected in 1989 on Old Skuna River, Skuna River Canal, and Skuna River Canal tributary in the vicinity of State Highway 9 at Bruce, Mississippi...................... 12 4. Estimates of near-future (10 to 20 years) channel-bank widening for Old Skuna River, Skuna River Canal, and Skuna River Canal tributary in the vicinity of State Highway 9 at Bruce, Mississippi.................................................. 27 5. Factor of safety and failure-block width for critical channel- bank failures on Skuna River Canal and Old Skuna River in the vicinity of State Highway 9 at Bruce, Mississippi........... 38 CONVERSION FACTORS AND VERTICAL DATUM Multiply By To obtain cubic foot per second (ft3/s) 0.02832 cubic meter per second feet per year (ft/yr) 0.3048 meter per year foot (ft) 0.3048 meter foot per mile (ft/mi) 0.1894 meter per kilometer foot per second (ft/s) 0.3048 meter per second inch (in.) 0.0254 meter mile (mi) 1.609 kilometer pound per cubic foot (lb/ft3) 157.1 newton per cubic meter pound per square foot (lb/ft2) 47.88 newton per square meter ry square mile (mi ) 2.590 square kilometer Mississippi Department of Transportation Datum: In this report, elevations are referenced to Mississippi Department of Transportation Datum (MDOTD)--a site- specific datum. At this site, elevations referenced to MDOTD are also to the National Geodetic Vertical Datum of 1929 a datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level Datum of 1929 and referred to in this report as sea level. VI DEFINITION OF TERMS Terms used in this report are defined below. Angle of internal friction -angle of the plane of Moisture content -ratio of the weight of the water contact of soil particles with the horizontal present to the weight of the soil solids (Das, at the point of sliding (shearing); angle whose 1984). tangent is the coefficient of friction between the soil particles (Cernica, 1982). Planar failure -slides along a surface of rupture whereby the mass progresses down and out Bulk-unit weight -ratio of the weight of the soil to along a planar or gently-undulatory surface the volume of the soil sample (Das, 1984). and has little rotational movement or backward tilting characteristics (Huang, Channel-bed aggradation -filling in of the 1983). channel because streamflows are not sufficient to transport the material delivered Rotational failure -landslide along a surface