Remote Sensing of Wave Overtopping on Dynamic Coastal Structures
Abstract
:1. Introduction
2. Materials and Methods
2.1. Experimental Setup
2.2. Lidar Measurements of Wave Overtopping
- An air void fraction α = 0 is assumed, however for violent overtopping flows on an irregular stone surface this is unlikely to be the case and will lead to an overestimate of overtopping volume. Indeed, very rapid overtopping flows were occasionally observed to “jump” as they passed over the revetment crest during 2DR leading to a short-lived air cavity beneath the overtopping flow. This effect led to anomalously large maxima in the depth timeseries during initial overtopping which were removed by discounting volume peaks during the first 0.25 s of these events.
- Infiltration into the porous revetment structure will mean that the estimated peak swash volume is smaller than the total amount of water that overtopped the crest. However, from an engineering perspective, the volumes presented here represent the flow volume actually present landward of the structure crest that could lead to safety concerns or inundation risk.
- As with the peak volume method, an air void fraction α = 0 is assumed, however for violent overtopping flows on an irregular stone surface this is unlikely to be the case. The presence of air voids will increase hc and lead to an overestimate of overtopping volume. Note that the flow “jumps” described above occur landward of the structure crest and so the large depths associated with this effect were not measured at the crest location.
- The flow depth at the structure crest was sometimes observed to be noisy during energetic overtopping events due to splashing, potentially leading to overestimates of the depth and hence overtopping volume. The depth data was despiked to remove short-lived depth maxima in order to minimise this effect.
- The shoreline velocity us is assumed to be representative of the depth-averaged flow velocity at the barrier crest uc. Schüttrumpf and Oumeraci [27] demonstrated that bore front velocity compared well with flow velocity measurements (micro-propeller) for waves overtopping an impermeable sea dike in the laboratory. In the current experiment, the irregular and porous nature of the structure may be expected to lead to enhanced deceleration of the swash front after overtopping. As a result, us is expected to provide a reasonable estimate of uc during the initial stages of overtopping but underestimate uc as flow reversal is approached.
3. Results
3.1. Comparison of Overtopping Measurement Methods
3.2. Overtopping Discharge at the Revetment Crest
3.3. Spatial Distribution of Overtopping Discharge
Implications for Dynamic Cobble Berm Revetment Design
3.4. Infiltration of Overtopping Volume
4. Conclusions
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
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Blenkinsopp, C.E.; Baldock, T.E.; Bayle, P.M.; Foss, O.; Almeida, L.P.; Schimmels, S. Remote Sensing of Wave Overtopping on Dynamic Coastal Structures. Remote Sens. 2022, 14, 513. https://doi.org/10.3390/rs14030513
Blenkinsopp CE, Baldock TE, Bayle PM, Foss O, Almeida LP, Schimmels S. Remote Sensing of Wave Overtopping on Dynamic Coastal Structures. Remote Sensing. 2022; 14(3):513. https://doi.org/10.3390/rs14030513
Chicago/Turabian StyleBlenkinsopp, Chris E., Tom E. Baldock, Paul M. Bayle, Ollie Foss, Luis P. Almeida, and Stefan Schimmels. 2022. "Remote Sensing of Wave Overtopping on Dynamic Coastal Structures" Remote Sensing 14, no. 3: 513. https://doi.org/10.3390/rs14030513
APA StyleBlenkinsopp, C. E., Baldock, T. E., Bayle, P. M., Foss, O., Almeida, L. P., & Schimmels, S. (2022). Remote Sensing of Wave Overtopping on Dynamic Coastal Structures. Remote Sensing, 14(3), 513. https://doi.org/10.3390/rs14030513