The determination of design parameters for coastal structures has historically often involved the definition of maximum water levels, the highest significant wave height and the longest wave periods The design then proceeds with these values using numerical models, direct design methods or physical model studies Design studies have often been conducted with maximum water levels, using random seas with previously determined parameters, a chosen wave spectrum and a sufficiently large number of waves Joint probability analysis methods using multiple parameters have identified that different combinations of water level; wave condition; perhaps fluvial discharge; or sea bed condition; may all influence the response
Recent research into the most important responses of vertical structures (plunging wave impact, toe scouring, overtopping and overtopping induced loading) indicates that these mechanisms are all linked to the occurrence of violent wave impacts Wave breaking is a depth-limited phenomenon, with plunging breakers occurring only for a limited range of wave height to water depth ratios For given storm wave heights, but tidally varying water levels, this wave breaking regime will often only prevail for a limited amount of time, leading to the conclusion that the duration of maximum exposure, ie the length of time that a coastal structure is exposed to the most important wave induced damage mechanisms, is a function of the combined probability of (at least) water level (tidal + storm surge) and wave height / storm profile characteristics This may have significant consequences for the definition of critical design parameters and the parameter variations employed in model tests

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The occurrence and effects of wave impacts

Effect of wave storm representation on damage measurements of breakwaters

Any stretch of a coastline warrants protection measure when it experiences an erosion rate beyond a threshold value, and when the seasonal littoral drift changes fail to restore equilibrium. The ca...

Sustainable hard and soft measures for coastal protection – Case studies along the Indian Coast

The effect of variations in water level on wave overtopping discharge over a dike: An experimental model study

In general, the groyne sections are made of rubble stones of different sizes. To conserve the ecosystem and also due to the scarcity of natural rocks around certain locations, the reliance on these hard materials for the construction of groyne sections becomes questionable forcing us to look for alternate eco-friendly soft materials, for example, geo systems. In order to evaluate the feasibility and advantages of geo systems for groyne construction and to test their hydrodynamic stability, the core section of rubble stones was replaced by geo-bags filled with sand. The objective of this study is to assess the wave transmission, hydrodynamic stability and wave overtopping of a groyne section with a geo-bags filled core section through physical model studies. The tests were conducted in a wave flume in Department of Ocean Engineering, Indian Institute of Technology Madras, India. A model scale of 1:15 is adopted based on Froude’s scaling law and dimensional limitations of the testing facility. The aforementioned cross sections were tested simultaneously in a wave flume that was partitioned longitudinally. The transmission and hydrodynamic stability of both the sections have been analysed by subjecting the corresponding sections to the action of random waves defined by JONSWAP spectrum through a well-controlled experimental programme. The details of test set-up, testing facility, parameters of model, test procedure, analysis of results and discussion will be reported in this chapter.

N. W. H. Allsop

Papers

6 Hydraulic modelling of rubble mound breakwaters