Small discrete object tracking on beaches and foreshore slope effect on cross-shore sediment transport
| Author(s) | Laksanalamai, Jirat | |
| Date Accessioned | 2024-10-29T16:42:20Z | |
| Date Available | 2024-10-29T16:42:20Z | |
| Publication Date | 2024 | |
| SWORD Update | 2024-10-13T19:02:28Z | |
| Abstract | The significant part of this study was to conduct an experiment in a wave flume to measure the trajectories of 20 small objects (gravel and microplastics) in the surf and swash zones on an equilibrium beach and a nourished foreshore beach with erosion and accretion in the swash zone. To develop a tracking model based on a kinematic Lagrangian model, the trajectory of each of the 20 objects was measured in six tests consisting of 100 runs with each run lasting 400 s. From the measurement, gravel particles were mobile only in the swash zone and moved seaward under wave downrush. Large and small microplastics moved onshore from the surf zone and accumulated in the lower swash zone of wave rundown or in the upper swash or berm zone of wave runup. Plastic particles remained on the evolving sand surface despite the erosion and accretion of the nourished foreshore. A simple tracking model is developed to predict the measured trajectories of the 20 particles of gravel and microplastics. The model was calibrated to predict limited net displacements of hypothetical sand particles on the equilibrium profile beach. For future applications, the tracking model may eventually be applied to track and clean up microplastics on beaches as well as to predict the destinations of sand particles placed on eroding beaches in beach nourishment projects. ☐ In countries where coastal engineering is developing, there is growing tendency to employ beach nourishment as coastal protection, despite limited wave data. This part of study introduces a simple analytical model proposed to estimate cross-shore sediment transport on a measured beach profile when wave data is unavailable. The model predicts offshore (onshore) sediment transport on the foreshore slope which is steeper (milder) than the equilibrium foreshore slope. A wave flume experiment was conducted to assess the model. Equilibrium, steep, and mild foreshores were constructed on a beach consisting of fine sand and exposed to identical irregular waves. The steep foreshore experienced rapid erosion, quickly transitioning to equilibrium, while accretion and equilibration on the mild slope occurred gradually. ☐ The calibrated model is able to predict the sediment transport rates on both the initial steep and mild foreshores with clear deviations from the equilibrium foreshore profile. The analytical model is furthermore compared with the nourished beach data at Pattaya, Thailand. Over the period from 2019 to 2023, bathymetric and topographic measurements were conducted yearly but water level and wave data were not measured. The analytical model is subsequently used to interpret the cross-shore sediment transport rate per unit width of the order of 10 m2/y and to estimate the degree of alongshore sand loss or gain. The simple model may eventually be extended to account for alongshore variability and become applicable to beach fill design. | |
| Advisor | Kobayashi, Nobuhisa | |
| Degree | Ph.D. | |
| Department | University of Delaware, Department of Civil and Environmental Engineering | |
| DOI | https://doi.org/10.58088/zkf0-4y84 | |
| Unique Identifier | 1504404429 | |
| URL | https://udspace.udel.edu/handle/19716/35473 | |
| Language | en | |
| Publisher | University of Delaware | |
| URI | https://www.proquest.com/pqdtlocal1006271/dissertations-theses/small-discrete-object-tracking-on-beaches/docview/3116105254/sem-2?accountid=10457 | |
| Keywords | Equilibrium profile | |
| Keywords | Lagrangian model | |
| Keywords | Microplastics | |
| Keywords | Sand | |
| Keywords | Sediment transport | |
| Keywords | Surf | |
| Keywords | Gravel | |
| Keywords | Swash | |
| Title | Small discrete object tracking on beaches and foreshore slope effect on cross-shore sediment transport | |
| Type | Thesis |