1. THREE-DIMENSIONAL MORPHOLOGY OF INTER- TIDAL BARS ON A MACRO- TIDAL BEACH Andrew Miles, Suzi Ilic and Alice Gent Funded by: Wyre Borough Council & Stena Line

2. Background  Find out about longshore sediment transport etc…

3. Background  This study is a part of the project looking into the feasibility of shoreface nourishment  Aim is to gain understanding of beach variability such as nearshore bar dynamic and sediment pathways  Relatively few field studies looked in 3D behaviour of intertidal bars in macro-tidal environment so called ridges  How does the bar system evolve over timescales of weeks to seasons?  Where and when do drainage channels form in the bar system? Are they persistent or ephemeral features?  What influence do coastal structures have on nearshore processes?

4. Study Site  Tidal Range 8-10m  Storm Surge > 1m  Waves  Mean Hs 0.5-1.0 m  Mean Tp 3-8 s  Multiple intertidal bars

5. Motivation for using Argus  Analysis of LiDAR images showed clear onshore movement of ridges  Field observations and numerical modelling suggest that the predominant sediment transport is longshore and northwards  Limitations of methods used for monitoring is the inability to monitor longshore sediment transport  Can evolution and longshore migration of drainage channels be monitored with Argus cameras?

6. Methodology

7. Drainage channel locations in 2012

8. Positions of the drainage channel (onshore mouth, middle and offshore mouth) within Argus FOV and Energy Flux

9. Bar dynamics from LiDAR images

10. Methodology  Wave breaking was used to identify bar locations  A number of states were identified  These were related to set of hydrodynamic conditions

21. Hydrodynamic conditions LLLD WWW WWDL o Little relationship was found between wave height and bar configuration o Stronger relationship was found with the predominant wave direction: the welding became more prevalent when there was a greater prevalence of oblique waves

22. Field measurements

23. 21/09 04/10 Bar is moving northwards Difference 21/09-04/10

24. Complex flow pattern as result of complex beach morphology The groyne system influence nearshore circulation Tides and waves influence sediment transport Hydrodynamic conditions

25. Discussion  Simple conceptual model of some of the key processes identified

26. Conclusion and further work  Three-dimensional nature of bar systems  Cross-shore and longshore processes need to be considered  Interaction of coastal structures, forming meandering and draining channels  Waves and tides have role in shaping nearshore morphology; tides are controlling the residence of breaking and shoaling waves  What about offshore conditions? How important are offshore changes? How important are tidal currents outside inter-tidal zone?

27. Study Site  Find out about longshore sediment transport etc…

28. Study Site  Find out about longshore sediment transport etc…

29. Migration of drainage channel and Energy Flux