profile (Okayasu and Katayama 1992). However, the other important factors: runup
flow, which determines the dynamics of periodically drained part of the beach and
fluctuating transport by infragravity and wind waves are poorly studied, but their
contribution is significant. This hampers quantitative description of the sediment
dynamics in this region. As a result, investigators use various interpolations in
modeling the evolution of the submarine slope profile without considering realistic
mechanisms of sediment transport.
While considering the morphodynamic problems in the conditions of
non-uniform bottom topography there is a need to calculate horizontal circulation
of water in the zone of transformation of breaking waves. At present, modern
numerical models of the coastal circulation have been developed based on the
concept of the radiation stress (Van Dongeren et al. 1994; Pechon and Teisson
1994), and Boussinesq equations (Sorensen et al. 1994). Unfortunately, these
models do not take into account the group structure of the waves approaching the
shore. In addition, these models are quite expensive in the sense of the consumption
of computer time. Their application for specific practical problems related to a large
number of time iterations is frequently inconvenient and not efficient. Therefore,
the problem remains pressing of selecting an economical hydrodynamic model,
which takes into account the influence of the group structure of waves adjusted to
the conditions of morphodynamic simulations and provides the acceptable accuracy
at minimum expenses.
In recent years, a number of investigations, related to the analysis of the
influence of frequency distribution of surface wave energy on the dynamics of the
bottom material, have been carried out (Kosyan et al. 2009; Divinsky et al. 2014). In
particular, it was found that under equal characteristics of irregular surface waves
the specific features of the wave forcing applied to the sandy bottom are determined
precisely by the peculiarities of the frequency distribution of wave energy. Concentration of the wave energy in the region of the frequency of the spectral
maximum facilitates a transition from irregular to regular waves and to the general
regulation of the dynamic impact on the solid bottom. In the physical sense, this
mechanism leads to the realization of more stable external conditions for the
development of microforms of bottom topography. These data are, of course, not
final, but nevertheless they allow us to formulate the general vector of future
research.
7.6 Conclusions
The coastal zone is the most dynamic part of seas and oceans. The enormous wave
power obtained from wind is damped precisely here. Formation of strong currents
and complex water exchange systems, formation and displacement of underwater
ridges, suspension and transport of large masses of sediments, etc. are the results of
energy dissipation. All these processes are interrelated in various combinations.
The state of shores and especially the state of beaches and coastal bottom
7 Lithodynamics of the Coastal Zone
129
flow, which determines the dynamics of periodically drained part of the beach and
fluctuating transport by infragravity and wind waves are poorly studied, but their
contribution is significant. This hampers quantitative description of the sediment
dynamics in this region. As a result, investigators use various interpolations in
modeling the evolution of the submarine slope profile without considering realistic
mechanisms of sediment transport.
While considering the morphodynamic problems in the conditions of
non-uniform bottom topography there is a need to calculate horizontal circulation
of water in the zone of transformation of breaking waves. At present, modern
numerical models of the coastal circulation have been developed based on the
concept of the radiation stress (Van Dongeren et al. 1994; Pechon and Teisson
1994), and Boussinesq equations (Sorensen et al. 1994). Unfortunately, these
models do not take into account the group structure of the waves approaching the
shore. In addition, these models are quite expensive in the sense of the consumption
of computer time. Their application for specific practical problems related to a large
number of time iterations is frequently inconvenient and not efficient. Therefore,
the problem remains pressing of selecting an economical hydrodynamic model,
which takes into account the influence of the group structure of waves adjusted to
the conditions of morphodynamic simulations and provides the acceptable accuracy
at minimum expenses.
In recent years, a number of investigations, related to the analysis of the
influence of frequency distribution of surface wave energy on the dynamics of the
bottom material, have been carried out (Kosyan et al. 2009; Divinsky et al. 2014). In
particular, it was found that under equal characteristics of irregular surface waves
the specific features of the wave forcing applied to the sandy bottom are determined
precisely by the peculiarities of the frequency distribution of wave energy. Concentration of the wave energy in the region of the frequency of the spectral
maximum facilitates a transition from irregular to regular waves and to the general
regulation of the dynamic impact on the solid bottom. In the physical sense, this
mechanism leads to the realization of more stable external conditions for the
development of microforms of bottom topography. These data are, of course, not
final, but nevertheless they allow us to formulate the general vector of future
research.
7.6 Conclusions
The coastal zone is the most dynamic part of seas and oceans. The enormous wave
power obtained from wind is damped precisely here. Formation of strong currents
and complex water exchange systems, formation and displacement of underwater
ridges, suspension and transport of large masses of sediments, etc. are the results of
energy dissipation. All these processes are interrelated in various combinations.
The state of shores and especially the state of beaches and coastal bottom
7 Lithodynamics of the Coastal Zone
129