Transient dynamics of storm surges and other forced long waves

Nielsen, P., Sebastien de Brye, Callaghan, D. and Guard, P. (2008) Transient dynamics of storm surges and other forced long waves. Coastal Engineering, 55 6: 499-505. doi:10.1016/j.coastaleng.2008.02.006


Author Nielsen, P.
Sebastien de Brye
Callaghan, D.
Guard, P.
Title Transient dynamics of storm surges and other forced long waves
Journal name Coastal Engineering   Check publisher's open access policy
ISSN 0378-3839
Publication date 2008-01-01
Year available 2008
Sub-type Article (original research)
DOI 10.1016/j.coastaleng.2008.02.006
Open Access Status
Volume 55
Issue 6
Start page 499
End page 505
Total pages 7
Editor Burcharth, H.F.
Place of publication Netherlands
Publisher Elsevier BV
Language eng
Subject C1
0905 Civil Engineering
960902 Coastal and Estuarine Land Management
Abstract The transient behaviour, i.e., the growth process of storm surges and other forced long waves is analysed through analytical solution to the small amplitude I D case. The growing long wave is modelled as the superposition of the asymptotic, steady forced solution and a pair of free waves which cancel it at time zero and subsequently move away from it, while perhaps decaying. This approach leads to useful new qualitative insights. First of all, it is clear that the timescale for the growth of a surge is L-surge/vertical bar root gh - c vertical bar, i.e., its length divided by the speed difference between the forcing and the free waves. Secondly, the surge landfall scenarios with fast versus slow moving low pressure systems are similar although the steady asymptotic responses are opposite. That is, even though the steady response to a fast (c>root gh) low pressure weather system is an ocean surface depression, the landfall scenario after a finite time is similar to that of a slow system, namely, a surface depression followed by a positive surge. Our superposition approach to the growth process also gives an understanding of the overshoot for multi-peaked or periodic surges. This phenomenon arises from the positive interference between the forced wave and free waves which have moved L/2 relative to each other after initially interfering negatively. The findings about landfall scenarios and overshooting are qualitatively valid for two horizontal dimensions as well. For unsteady forcing, e.g., a gradually intensifying low pressure system, the final forced wave still has the shape of the forcing, but the free waves end up with very different shapes which are generally flatter. The analytical solution also gives an understanding of the free-wave-pattern which remains after the forcing has disappeared. Finally, friction free, non-resonant surges grow initially as ? and maximum growth occurs at the points of maximum curvature of the forcing. For the resonant case, the initial growth of the surge is linear with time and the shape of the resonant surge corresponds to partial derivative f/partial derivative x where f(x-ct) is the shape of the forcing. (C) 2008 Elsevier B.V. All rights reserved.
Keyword Engineering, Civil
Engineering, Ocean
Engineering
ENGINEERING, CIVIL
ENGINEERING, OCEAN
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: 2009 Higher Education Research Data Collection
School of Civil Engineering Publications
 
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Citation counts: TR Web of Science Citation Count  Cited 7 times in Thomson Reuters Web of Science Article | Citations
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Created: Fri, 27 Mar 2009, 19:35:10 EST by Katherine Montagu on behalf of School of Civil Engineering