Wave Overtopping and Coastal Structures - Essay Example

Part Two: Wave Overtopping on Coastal Structures Introduction: In the earlier parts of the paper a set of formulae developed by separate groups of researchers have been used to compare results of wave overtopping discharge volumes and individual wave overtopping volumes to investigate how each of these formulae approach the overtopping problem that poses a threat to coastal structures. Wave structural parameters used had been acquired from Shao, 2006, and it had been found that those former parts that the Shao, 2006, turbulence model was the most appropriate as it took into consideration a larger number of parametric values pertaining to wave and coastal protection structures. Nevertheless, the other formulae, listed hereafter, also still merit some consideration and they have been used in this part of the paper, in conjunction with that of Shao, 2006. The motive this time is to use wave and structural data other than that of Shao, 2006, to investigate what wave parameters pose the maximum threats to coastal structures with given parameters. This, it is sincerely believed, will allow future researchers to better prepare for dangerous and possible wave overtopping real-time events. The formulae utilised in the former parts of the paper are as follows. 1. The Weggel (1976) Overtopping Volume Formula (Cui, 2004); 2. The Battjes Overtopping Volume (Source: Cui, 2004); 3. The Daemrich et al, 2006; Q = , where , where = deepwater wave height; = deepwater wavelength; = slope of seawall; , as per Daemrich et al, 2006, is the breaker parameter. 4. The HR Wallingford Ltd., 1999; The maximum individual overtopping volume per metre run of seawall for a sequence of waves is given by: = a (Eqn. 46, Box 4.5, p.31, Wallingford, 1999), where a, b are empirical coefficients and is the number of overtopping waves in the sequence . For sloped seawalls and for = 0.02 (= wave steepness) a = 0.85 and b = 0.76 (Box 4.5, p.31, Wallingford, 1999),. = mean individual overtopping discharge volume). (Eqn. 37, p.27, Wallingford, 1999). The Wallingford equation is valid for 5. Wave Overtopping Volume: It is significant that overtopping discharge and, in essence, individual overtopping volume in effect, are highly sensitive to even very small changes in seawall geometry, local bathemetry and wave climate (Wallingford, 1999). The strategy this paper adopts to investigate influence of wave parameters on seawall efficiencies is simple. A number of variant sets of parameters are used to test mean overtopping discharge possibilities. Mean Overtopping Discharge: 1. An initial seawall slope of 1:5 is taken with wall height (taken as the wall freeboard for crest above still water level) = 1m and wall length () = 5.6m. The significant wave height () is kept at 0.85m, while the wavelength is assumed to be 4.25m. The wave period (), though, is varied to 1.2s. With this configuration, the Wallingford overtopping volume model is applied. It is also assumed that there are 10 waves in a series. = .2888 (Equation valid as per Wallingford, Box 3.1, p. 10, 1999; for 0.05 Read More