Transient dynamics of storm surges and other forced long waves

Nielsen, Peter; Brye, Sébastien de; Callaghan, David P.; Guard, Paul

doi:10.1016/j.coastaleng.2008.02.006

Cited by 13 publications

(9 citation statements)

References 7 publications

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“…Furthermore, it is suggested that equation 2.12 is valid only for a mild transition from the undisturbed to the disturbed zone, while abrupt changes would lead to more complex solutions. This seems to corroborate Nielsen et al (2008), who showed that the gradual perturbation in the forced solution stretches and reduces the amplitude of the free waves. In other words, in the perturbation limit, the free long waves vanish (further discussion on the gradual changes in the forcing is in Section 3.5, Figure 3.17).…”

Section: Bound Waves -Steady and Transient Conceptssupporting

confidence: 76%

“…The bound wave release mechanism proposed by Nielsen et al (2008) has been numerically investigated. For a horizontal bottom it was demonstrated that by stretching the region of the forcing decay (similar to short wave dissipation in the surf zone) the amplitude of the released bound wave was reduced when compared to the same bound wave released during an abrupt removal of the forcing.…”

Section: Research 71 Summary Of Conclusionmentioning

confidence: 99%

“…Recently Nielsen et al (2008) taking the constant in equation 2.6 as zero, the bound wave becomes purely negative. Therefore, to conserve mass, any change in the non-homogeneous part is balanced by the homogeneous part, which propagates with ± √ gh, i.e.…”

Section: Bound Waves -Steady and Transient Conceptsmentioning

confidence: 99%

“…From the interpretation of the transient solution for linear long waves forced by the horizontal gradients of the radiation stress, Nielsen et al (2008) suggested a mechanism for the conversion of forced wave into free wave (an analogy to bound wave release). The same approach may also suggest a mechanism for bound wave decay in the surf zone without any dissipation term.…”

Section: Infragravity Wave Dissipation and Bound Wave Releasementioning

confidence: 99%

“…Three possible hypothesis for the observed infragravity wave decay, after short wave breaking, were analyzed. Nielsen et al (2008) proposed a mechanism for the conversion of a forced wave into free waves (an analogy to bound wave release). According to this approach, a reduction in the released wave amplitude is expected for a gradual forcing decay, as exemplified in Figure 3.17.…”

Section: Infragravity Wave Dissipation and Bound Wavementioning

confidence: 99%

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Infragravity wave forcing in the surf and swash zone

Moura¹,

Rolim²

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Infragravity waves, also known as surf beat, are important morphodynamic drivers in shallow water, especially inside the surf and swash zone where the short wave energy is dissipated due to breaking. In the past decades, great progress has been acquired in the understanding of surf beat and its implication in the coastal environments. However, many key features are still not fully understood, especially for complex natural systems. This thesis investigates infragravity wave dynamics in the surf and swash zone through a re-analysis of laboratory data, new numerical modelling and novel field measurements.The generation of infragravity waves in the surf zone is commonly associated with two individual mechanisms: release of second-order group-forced long waves and long waves generated by group-induced surf zone breakpoint oscillations. Both mechanisms are forced by radiation stress gradients, but due to their individual nature, different relationships between short and infragravity waves are expected.Determining these relationships, their effectiveness, and the governing hydrodynamic and morphodynamic conditions for each mechanism is complex. In the field, observations are still, to some extent, limited and generally restrained to small wave conditions. The first part of the thesis presents a comprehensive study of different infragravity wave generation mechanisms that includes a critical literature review, a re-analysis of previous laboratory data and an extensive numerical modelling investigation.This work provided new information about the implication of the different processes associated to bound wave shoaling, release and dissipation. In addition, key aspects related to the propagation patterns of infragravity waves have been identified. From the numerical investigation and the large amount of laboratory data re-analysed, clear and distinct relationships between the breakpoint and shoreline excursion have been established for each generation mechanism. The second part of the thesis presents a novel method to determine the dominant infragravity mechanism in the inner surf and swash zone in the field. In the field, the breakpoint oscillations and the shoreline motion are measured remotely via video and ii their relationship identified via cross-correlation. The identification of the dominant forcing mode, either bound wave or breakpoint, is interpreted based on the specific relationships previously determined.The results of thirteen field data sets collected from three different beaches indicate that, inside the surf zone, the dominance of bound wave or breakpoint forcing is strongly dependent on the surf zone width and the type of short wave breaking.Infragravity generation by bound wave release was stronger for conditions with relatively narrow surf zones and plunging waves; breakpoint forcing was dominant for wider surf zones and spilling breaker conditions, suggesting also that the bound waves remained forced inside the surf zone, being dissipated during short wave breaking. The numerical and laborato...

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Section: Bound Waves -Steady and Transient Conceptssupporting

confidence: 76%

Section: Research 71 Summary Of Conclusionmentioning

confidence: 99%

Section: Bound Waves -Steady and Transient Conceptsmentioning

confidence: 99%

Section: Infragravity Wave Dissipation and Bound Wave Releasementioning

confidence: 99%

Section: Infragravity Wave Dissipation and Bound Wavementioning

confidence: 99%

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Infragravity wave forcing in the surf and swash zone

Moura¹,

Rolim²

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Local amplification of storm surge by Super Typhoon Haiyan in Leyte Gulf

Mori

Kato

Kim

et al. 2014

Geophysical Research Letters

193

124

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Typhoon Haiyan, which struck the Philippines in November 2013, was an extremely intense tropical cyclone that had a catastrophic impact. The minimum central pressure of Typhoon Haiyan was 895 hPa, making it the strongest typhoon to make landfall on a major island in the western North Pacific Ocean. The characteristics of Typhoon Haiyan and its related storm surge are estimated by numerical experiments using numerical weather prediction models and a storm surge model. Based on the analysis of best hindcast results, the storm surge level was 5–6 m and local amplification of water surface elevation due to seiche was found to be significant inside Leyte Gulf. The numerical experiments show the coherent structure of the storm surge profile due to the specific bathymetry of Leyte Gulf and the Philippines Trench as a major contributor to the disaster in Tacloban. The numerical results also indicated the sensitivity of storm surge forecast.

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