Conclusions. What else do we need to know about wave breaking? - Breaking and Dissipation of Ocean Surface Waves - page 418

Many more breaking-related topics can be mentioned, but were not included in this topic.
One set of such applications is the breaking in finite water depths and shallow waters.
These topics are depth-limited wave development, i.e. forecast of waves in finite-depth
environments, surf-zone breaking (we mention it here, separately from the finite-depth
conditions, for obvious reasons), and wave-bottom interactions, including sediment sus-
pension and transport, among many others. While the ultimate criteria for wave breaking,
i.e. the conditions (steepness) of the water surface when it loses stability and starts col-
lapsing, should be similar in deep and finite waters, the physics of the processes leading
to the breaking onset and of the outcomes of the breaking event can be very different. In
many regards, the wave breaking and certainly the dissipation in finite and shallow depths
is another research field rather than an extension of the deep-water topic into a new envi-
ronment (e.g. Thornton & Guza , 1983 ; Herbers et al. , 2000 , 2003 ; Lowe et al. , 2005 , 2007 ;
Rogers &Holland , 2009 ). In the present topic, the issue of the limiting steepness and break-
ing probability in finite depths is discussed in Section 5.3 , but the overall topic is left to
other topics.
Among many more wave-breaking-related research areas, which are not addressed in
this topic, or not addressed in any detail, we can mention wave breaking in the presence of
currents, remote sensing applications of wave breaking, and engineering tasks. The latter
set deals with a variety of problems, whose solutions have to be different to those research
products sought after in this topic and whose significance covers the needs of marine trans-
port, including underwater pipelines, navigation, ship design, coastal and offshore indus-
tries, maritime safety issues, pollution mitigation, naval exercises, fishery, recreational
activities at sea, and many others. Typical engineering problems are the impacts of the
breaking waves on structures or on the bottom in shallow areas, and suspension of the sed-
iment and generating currents to carry out long-shore and cross-shore sediment transport,
among many others.
With this, we finish the summary of what we know about the breaking and open the
discussion. The topic of the discussion is the sub-title of the current Chapter 10 : “What
else do we need to know about wave breaking?”
In terms of wave breaking as such, much essential progress has been made lately in
understanding what is the breaking onset and in describing the breaking probability. That
is we can, with reasonable confidence, answer the question of why waves break. Hand in
hand with that, the breaking probability is sufficiently well described and even quantita-
tively parameterised both for monochromatic two-dimensional wave trains and for oceanic
directional wind-forced waves with a continuous spectrum, even for those in finite depths.
In this regard, it is worth mentioning again that field investigations of the breaking
onset and of micro-breaking, which seem quite difficult because these are features where
whitecapping-related properties cannot be employed, can be approached by radar moni-
toring of sea spikes. As discussed in Section 3.6 , the radar measurements do detect the
incipient breakers rather than breakers in progress and are one of the oldest experimental
means of wave-breaking investigations, but for some reason they are essentially under-used
in wave-breaking research. This is particularly surprising as they can even estimate orbital