Abstract
The effects of climate change with increased sea level and intensity of the extreme storms leads to an increase of the loads and of the expected overtopping at existing seawalls. The inclusion of bull-noses in the design of seawalls seems to significantly reduce the wave overtopping discharge q and may be an effective solution to face climate change while limiting the increase of the seawalls height and the costs. The experimental work by Van Doorslaer et al. (2015), VD hereinafter, is the only systematic study available so far about the effects of bull-noses on the reduction of q. They developed a number of formulae, adopted then by EurOtop (2016), in case the seawall is placed on a dike slope or at the end of a promenade. The work we are proposing here starts from these findings, to analyze a different case: dikes with a finite crest width and an inshore crown wall with and without a bull-nose. The aim is to verify whether the formulae developed by VD can still be used or require some modifications to complete the existing design formulae.
Highlights
The effects of climate change with increased sea level and intensity of the extreme storms lead to an increase of the loads and of the expected overtopping at existing seawalls
Focusing on the typical geometry of the Belgian coastlines, and on non-breaking waves conditions exclusively, they developed a number of formulae, adopted by EurOtop (2016), to parametrize the combined effect of wall, bullnose and berm, in case the crown wall is placed on the dike slope or at the end of a promenade
The work we are proposing here starts from these findings, to analyze a different case: dikes with a finite horizontal crest width and an inshore crown wall, with and without a bullnose, subjected to both breaking and non-breaking wave conditions
Summary
The effects of climate change with increased sea level and intensity of the extreme storms lead to an increase of the loads and of the expected overtopping at existing seawalls. The values of q derived from the reservoirs were compared to the values of q obtained by integrating the flow velocities (u) with the corresponding water depths (h) registered at 2 gauges placed at the off-shore and in-shore edges of the crown-walls (see Figure 2), obtaining a good agreement of the results from the 2 methods These estimations of q are conceptually comparable to the measurements of q from the weighing boxes by VD and to the results of the experimental investigations presented below in this contribution. The original set of structures tested by Formentin & Zanuttigh (2018), consisting of smooth dikes with different offshore slopes cotαd (4, 6), various wall freeboards Rc/Hs (in the range [-1.5; +1.5]) and constant berm width B (3 m), was enlarged and modified to include the presence of the crown walls with and without bn, see Figure 1.
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