Soichi Harikai

Bio: Soichi Harikai is an academic researcher. The author has contributed to research in topics: Breaking wave & Longshore drift. The author has an hindex of 2, co-authored 2 publications receiving 119 citations.

Shoreline Change at Oarai Beach: Past, Present and Future

Abstract: Large breakwaters and groins are being constructed at Oarai Harbor, Japan. As a result the beach is significantly deforming. The first part of this paper documents past and recent shoreline change at Oarai. The general characteristics of the offshore waves, breaking waves, and longshore current pattern are described and used to explain qualitative features of the observed shoreline change. The second part presents results of numerical simulations of shoreline change at the site which occurred over different time periods. The model includes three sources of wave diffraction, a rigorous formulation of the seawall boundary condition, and sand bypassing at groins. The modeling of historical shoreline change was reasonably successful. As an exercise in investigating problems associated with prediction, the model was used to forecast the shoreline position at the site five years from now. The prediction of the wave history was the main problem encountered. A simple intuitive method was devised to estimate the probable range in variation of the wave history, and the results are discussed in connection with the shoreline forecast.

Genesis-A Generalized Shoreline Change Numerical Model

Abstract: This report describes a numerical model called GENESIS ( GENE ralized model for SI mulating S horeline change), developed for calculating shoreline change as caused primarily by wave action. The modeI is based on the one line theory, for which it is assumed that the beach profile remains unchanged, thereby allowing beach change to be described uniquely in terms of the shoreline position. As opposed to previous models based on the same concept, GENESIS is generalized in the sense that a simple user Interface allows the system to be applied to a diverse variety of situations involving almost arbitrary numbers, locations, and combinations of groins, jetties, detached breakwaters, seawalls, and beach fills. Other features included in the system are wave shoaling, refraction, and diffraction; sand passing through and around groins, and sources and sinks of sand. An overview of the modeling system is presented, and comparisons to analytic solutions as well as prototype situations are presented to demonstrate the capabilities of the system.

Shorerise and bar-berm profiles on ocean beaches

Abstract: A beach equilibrium model is developed that treats the outer (shorerise) portion of the profile independently from that of the inner (bar-berm) portion. The two portions are matched at the breakpoint-bar. The partitioning of the profile in this way is consistent with the different forcing modes on either side of the breakpoint. This formulation utilizes beach profile data not previously available. It is shown that both portions of the profile are well fitted by curves of the form h = Axm, where h is positive downward and x is the positive offshore coordinate. Surprisingly, the value of m ≈ 0.4 is nearly the same for shorerise and bar-berm and does not change significantly with seasonal beach changes (summer/winter). The principal difference between seasonal profiles is that in winter (higher waves) the breakpoint-bar is deeper and farther offshore while the berm crest is displaced landward. Thus the changes in seasonal equilibria are manifested by simple, self-similar displacements of the bar-berm and shorerise curves as a consequence of changes in surf zone width and O(1) variations in the factor A.