1. River Meanders Outline Primary flow characteristics within a meander bend Flow and sediment transport within meander bend Controls on meander wavelength Meander migration and shift

2. Red River, near Aubigny, southern Manitoba

3. Turkey River, Clayton County, IA

4. Pecatonica River near Mineral Point, WI

6. (Bridge, 2003) Plan Cross section

7. Primary Flow Characteristics Flow-transverse component of water surface slope towards the inner bank Secondary flow pattern (spiral or helical flow) due to –(a) curvature-induced centrifugal forces and –(b) pressure gradient of the transverse sloping water surface –Effects proportional to velocity and inversely proportional to radius of curvature Flow field is stage-dependent

8. (Hey and Rainbard, 1996) Point bar (inner bank)Outer bank Secondary flow pattern in a meander bed

9. Balance between centrifugal force and pressure gradient

10. (Bridge, 2003) Observed for River South Esk Simulated Mean Flow Velocity Predicted

11. (Bridge, 2003) Outside Inside Simulated

12. (Bridge, 2003) Observed for River South Esk Simulated Water Surface Topography Predicted

13. (Bridge, 2003) Observed for River South Esk Simulated Flow Depth Predicted

14. (Bridge, 2003) Observed for River South Esk Simulated Relative Bedload Transport Rate Predicted

15. (Bridge, 2003) Observed for River South Esk Simulated Bedload Grain Size Predicted

17. (Knighton, 1998) Maximum shear stress Flow field Secondary flow Flow structure

18. (Julien, 2002) Controls on Meander Wavelength   W  12.34W  r c  4.59r c 0.98 Combining:  r c ~2 to 3W

19. (Julien, 2002) Controls on Meander Wavelength  Q b b ; b~0.5

20. (Knighton, 1998) Meander Movement

22. (Knighton, 1998) Types of Meander Growth and Shift

23. (Julien, 2002) Shear Stress and Meanders  t0  hU 2 /r c  t0 00  t max   m    t high  when r c ~2.5W

24. Meanders and River Restoration Links channel process with form Designing or creating meandering rivers appears to be optimal channel form used in river restoration Provides the boundary conditions for the hydraulic stability of a meandering planform

25. River Meanders Conclusions Spiral or helical flow in meander bend is a balance of centrifugal and pressure gradient forces All flow, bed, and sediment parameters then are modified by this flow pattern Meander wavelength can be determined from width and discharge relations