scholarly journals BEACH PROFILE CHANGE UNDER VARYING WAVE CLIMATES

1988 ◽  
Vol 1 (21) ◽  
pp. 114
Author(s):  
Yen Kai ◽  
Ren Rushu ◽  
Wang Liang

In the present paper results of experimental study of two-dimensional transformation of sandy beach under varying wave climates are presented. The varying wave climates were composed of different systems of regular waves exerted one after another on the model beach. Through experiments it was found that sandy beach transformation within surf zone could be expressed by the changes of characteristic point A and characteristic slope tan 13, and that although the expression for beach erosion-accretion criteria is dimensionless, similitude scale effects should still be taken into consideration.

1986 ◽  
Vol 1 (20) ◽  
pp. 106
Author(s):  
Hitoshi Nishimura ◽  
Tsuguo Sunamura

This paper presents an overall numerical model for predicting beach profile changes due to waves. The local rate of net on/offshore sediment transport is empirically formulated as a function of the Ursell number and Hallermeier parameter. A sub-model of two-dimensional wave transformation includes the wave shoaling, breaking and damping in a surf zone. It is combined with another sub-model of beach profile change for the analyses of wave-profile interaction. The validity of the model is examined through hindcasting of profile changes observed in ordinary and prototype-scale flumes.


1986 ◽  
Vol 1 (20) ◽  
pp. 102 ◽  
Author(s):  
Nubuo Mimura ◽  
Yukinori Otsuka ◽  
Akira Watanabe

In the present study, effects of irregular waves on two-dimensional beach transformation and related phenomena were investigated through a series of laboratory experiments. Attempts were made to determine a representative wave of irregular wave trains which controlled individual phenomenon related to the two-dimensional beach profile change. It was found that the representative wave is different for each phenomenon. For the macroscopic beach profile change, it is the mean wave which represents whole incident waves. On the other hand, some of microscopic phenomena, such as initiation of sand movement and sand ripple formation, are controlled by larger waves in the wave train selectively, of which representative wave is the significant wave.


2001 ◽  
Vol 45 (03) ◽  
pp. 216-227
Author(s):  
R. Centeno ◽  
K. S. Varyani ◽  
C. Guedes Soares

An experimental program was performed with hard-chine catamaran models in regular waves. The distance between the demi-hulls of the models was changed to assess its effects on the wave-induced motions. The results allowed the study of some aspects related to catamaran motions, like the interference between the hulls and resonance frequencies. The experimental results are compared with calculations performed with a recently developed code based on a two-dimensional potential flow theory in which viscous forces are included through a cross-flow drag approach. The effect of the hull distance in the heave and pitch motion responses and the importance of the viscous forces in such hull configurations are shown.


1982 ◽  
Vol 1 (18) ◽  
pp. 85 ◽  
Author(s):  
Ryoichi Kajima ◽  
Takao Shimizu ◽  
Kohki Maruyama ◽  
Shozo Saito

Two-dimensional beach profile changes were investigated with a newly constructed prototype-scale wave flume. The flume is 205 m long, 3.4 m wide and 6 m deep. Sand of two grain sizes was used in the experiments. Analysis of the results was made through use of the parameter C, introduced by Sunamura and Horikawa (1974) to classify beaches as either erosional and accretionary. Beach profile changes obtained in the flume were similar to those in the prototype (field). Net sand transport rate distributions were classified into five types, two of which do not seem to have been observed in laboratory (smallscale) experiments. A simple model describing the five types was developed for evaluating two-dimensional beach profile changes.


1980 ◽  
Vol 1 (17) ◽  
pp. 71 ◽  
Author(s):  
Masataro Hattori ◽  
Ryoichi Kawamata

In this paper a model is presented to describe onshore-offshore sand transport in the surf zone. The model is based on the physical consideration that when the net transport attains a state of equilibrium, the power expended through gravitational force in suspending sand grains is balanced by that due to the uplifting force arising from the turbulence generated by breaking waves. Two important parameters controlling sand transport are the dimensionless fall-time parameter and bottom slope.


1986 ◽  
Vol 1 (20) ◽  
pp. 87 ◽  
Author(s):  
T.W. Hsu ◽  
S.R. Liaw ◽  
S.K. Wang ◽  
S.H. Ou

A two-dimensional empirical eigenfunction model is proposed for the analysis and the prediction of beach profile change due to longshore and cross-shore sediment transports. Beach profile data from Redhill coast, Taiwan, measured every two months at 150 meters interval along the detached breakwaters are analyzed and the relative importance from two directions is investigated. Furthermore, by employing the method of Markov process and linear regression, a prediction model is formulated which takes into account the effect of breaking waves, bottom sediment and radiation stress of waves. This 2-D model is shown to be effective in the analysis and the prediction of beach changes near the coastal structures.


1982 ◽  
Vol 1 (18) ◽  
pp. 88 ◽  
Author(s):  
Tomoya Shibayama ◽  
Kiyoshi Horikawa

Laboratory and field investigations were performed in order to formulate a predictive model of two-dimensional beach profile change. The observed transport was classified into six types, and transport formulas were deduced for each type based on a microscale description of sediment movement caused by wave action. A numerical model of two-dimensional beach transformation was then developed. Beach profile changes calculated with the model were then compared with the laboratory results. The model was found to give reasonable results except in the vicinity of the wave plunging point. The sediment transport calculation is based on a sinusoidal velocity profile. The model appeares to give good results as long as the wave motion can be reasonably approximated by linear wave theory.


1988 ◽  
Vol 1 (21) ◽  
pp. 96 ◽  
Author(s):  
Magnus Larson ◽  
Nicholas C. Kraus ◽  
Tsuguo Sunamura

An empirically based engineering numerical model is presented for simulating beach profile change in the surf zone produced by waveinduced cross-shore sand transport. The model simulates the dynamics of macroscale profile change, such as the growth and movement of berms and breakpoint bars. Model development was founded on two data sets from large wave tank experiments consisting of 42 cases with different incident wave conditions, median grain size, and initial beach shape. Model predictions are tested with field data, and reasonable agreement is found.


Author(s):  
Jie Zhang ◽  
Magnus Larson ◽  
Zhenpeng Ge

Beach profile change induced by storms is a common and complex process in coastal engineering. Storms often bring high water levels and large waves, which erode the berm and dune, carrying large quantities of sand offshore, often causing severe damage to coastal properties. Thus, considerable research has been carried out to determine storm impact. Early studies mainly focused on laboratory investigations and analysis of field data. Since the 1980’s, many engineering numerical models of beach profile change have been developed. Kriebel and Dean (1985) proposed a model (EBEACH) to simulate the beach profile evolution with focus on dune erosion during storms, using the concept of an equilibrium beach profile (EBP). However, features such as bars and berms are not described in this model. Larson and Kraus (1989) developed an empirically based model (SBEACH) for describing the formation of bars and berms, also applying the EBP concept. Steetzel (1990) developed a model for cross-shore transport during severe storms that focuses on offshore transport and erosion. Johnson et al. (2012) developed a CS profile evolution model, CSHORE, that is mainly used to predict beach erosion under the combined effect of waves and currents. Although the model provided satisfactory performance in simulating measured berm and dune erosion in field applications, further improvements in dealing with the sediment transport in the intermittently wet-dry areas are desirable. At present, XBeach proposed by Roelvink et al. (2009) is the most popular and widely used model together with SBEACH. Although the objective of the XBeach model is to predict the profile evolution along the entire profile, i.e., both in the subaerial and subaqueous regions, the processes in the former region are less well described from a physics point of view compared to the latter. The response of the subaerial region in XBeach, including the foreshore, berm, and dune, relies on rather ad-hoc empirical sediment transport formulations. This study presents a profile evolution model that is based on the work by Larson et al. (2015). The emphasis of the model development is physically based descriptions of the subaerial profile response induced by storms. Focus of the model validation here is the berm and foreshore region.


1984 ◽  
Vol 1 (19) ◽  
pp. 46 ◽  
Author(s):  
Masaur Mizuguchi

A field measurement was conducted in order to clarify the swash motion on a natural beach. It is found on this particular beach, which had a rather steep foreshore slope, that cross spectra calculated between the surface elevations, onshore velocities and the swash agree very well with those given by linear long two-dimensional standing wave theory in the lower frequency region than a certain value. This finding together with the observed f~ (f; frequency) high frequency saturation in swash spectra encourages a partial reflection model to describe the fluid motion in the inner surf zone, including the swash. The model developed shows a good agreement with the observed results, in which being employed an analogy to regular waves for the criticality of wave reflection. This model makes it possible to predict the swash spectrum for a given incident wave spectra and a given beach profile, as far as wave breaking takes place on a foreshore slope.


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