Concept Of Equilibrium Beach Profile Research Articles

A MODEL TO SIMULATE BEACH PROFILE EVOLUTION INDUCED BY STORMS

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.

Local Wave Energy Dissipation and Morphological Beach Characteristics along a Northernmost Segment of the Polish Coast

Abstract This paper analyses cross-shore bathymetric profiles between Władysławowo (km 125 of the Polish coastal chainage) and Lake Sarbsko (km 174) done in 2005 and 2011. Spaced every 500 m, they cover beach topography from dune/cliff crests to a seabed depth of about 15 m. They were decomposed by signal processing techniques to extract the monotonic component of beach topography and to perform a straightforward assessment of wave energy dissipation rates. Three characteristic dissipation patterns were identified: one associated with large nearshore bars and 2–3 zones of wave breaking; a second, to which the equilibrium beach profile concept can be applied; and a third, characterized by mixed behaviour. An attempt was then made to interpret these types of wave energy dissipation in terms of local coastal morphological features and the underlying sedimentary characteristics.

Empirical Equilibrium Beach Profiles Along the Eastern Tombolo of Giens

Beaches along the eastern branch of the Giens double tombolo are subject to coastal erosion. Prediction of the behavior of the beach profile configuration in response to natural and anthropogenic changes using the concept of equilibrium beach profile (EBP) could be useful in finding the most suitable measure to address the erosion problem. Field investigation data of 11 beaches along the eastern tombolo were supplied for this study, and a nonlinear fitting technique was applied to estimate the best parameter values of seven empirical formulations of the relevant EBP. All of the observed beach profiles could be described by a single function, but a single EBP was inadequate to represent all of the beach profiles observed. The variation found could be explained in terms of longshore variation of bathymetry, sediment size, and wave parameters. Analysis of the validity of the EBPs revealed that a representative EBP of each beach is governed by different equilibrium parameters.

Analysis of Shoreline Response due to Wave Energy Incidence Using Equilibrium Beach Profile Concept

Analysis of Shoreline Response due to Wave Energy Incidence Using Equilibrium Beach Profile Concept

Some characteristic wave energy dissipation patterns along the Polish coast

Summary The paper analyses cross-shore bathymetric profiles between Wladyslawowo (km 125 of the national coastal chainage) and Lake Sarbsko (km 174) commissioned in 2005 and 2011 by coastal authorities for monitoring purposes. The profiles, spaced every 500 m, cover beach topography from dune/cliff tops through the emerged beach to a seabed depth of about 15 m. They were decomposed by signal processing techniques to extract their monotonic components containing all major modes of the variability of beach topography. They are termed empirical equilibrium profiles and can be used for straightforward assessment of wave energy dissipation rates. Three characteristic patterns of wave energy dissipation were thus identified: one associated with large nearshore bars and several zones of wave breaking; a second, to which the equilibrium beach profile concept can be applied; and a third, characterized by mixed behaviour. Interestingly, most profiles showed significant seabed variations beyond the nearshore depth of closure – this phenomenon requires comprehensive studies in future.

Quantification of changes in the beach volume by the application of an inverse of the Bruun Rule and laser scanning technology

We address the possibilities of combining terrestrial (TLS) and airborne laser scanning (ALS) techniques with the classical concept of equilibrium beach profile to quantify the changes in the total sand volume of slowly evolving sandy beaches. The changes in the subaerial beach are determined from a succession of ALS surveys that were reduced to the same absolute height using a TLS survey of a large horizontal surface of constant elevation. The changes in the underwater sand volume from the waterline down to the closure depth are evaluated using an inverse of the Bruun Rule. The relocation of the waterline is extracted from the ALS scanning of elevation isolines of 0.4-0.7 m. The method is applied to an about 200 m long test area in the central part of Pirita Beach (Tallinn Bay, north-eastern Baltic Sea). The sand volume in this area exhibits extensive interannual variations. The annual gain of sand in the entire beach was about 2000 m 3 /y in 2008-2010 and the annual loss was about 1100 m 3 /y in 2010-2014. The changes in the underwater part of the beach are by a factor of 2-2.5 larger than the changes in the

Equilibrium shoreline modelling of a high-energy meso-macrotidal multiple-barred beach

Abstract 8-year time series of incident wave energy and monthly alongshore-averaged beach surveys at the high-energy meso-macrotidal multiple-barred Truc Vert beach are analysed. We apply two behaviour-oriented equilibrium shoreline models that relate the rate of cross-shore shoreline displacement to the wave energy and the wave energy disequilibrium between the wave energy and the equilibrium wave energy that would cause no change to the present shoreline location. The two models show similar skill. Results show that the equilibrium shoreline model concept works on meso-macrotidal multiple-barred beaches, with similar skill when applied to non-barred and/or micro-mesotidal beaches, provided that a relevant shoreline proxy is used. Simulations show that Truc Vert beach responds predominantly at seasonal timescales rather than at individual storm frequency. The first winter storms drive the most pronounced erosion events because both the wave energy disequilibrium and erosion change potential are large. The best shoreline proxy at Truc Vert beach is the mean high water level, where the inner-bar and berm dynamics have little influence on the shoreline cross-shore displacement. Implications for shoreline monitoring through video imagery on this type of beach are discussed. Results also reveal that the equilibrium shoreline concept can be extended to an equilibrium beach profile concept pending further improvements.

Physical modeling of intermediate cross‐shore beach morphology: Transients and equilibrium states

Laboratory experiments on cross‐shore beach morphodynamics are presented. A lightweight sediment (density ρs = 1.19 g cm−3) model is used in order to fulfill a Shields number and Rouse number scaling. This choice aims at correctly reproducing bed load transport as well as suspension dynamics. Terraces and barred beach profiles obtained in the experiments also present close similarities with profiles observed in the field. In order to question the concept of equilibrium beach profile, wave forcings conforming to a JONSWAP spectrum were imposed over long periods (up to more than a hundred hours). An average bottom evolution velocity is defined and used to determine when the profile reaches equilibrium. Usually, beach profiles are characterized according to the Wright and Short (1984) classification based on the Dean number Ω. This well‐known classification is investigated and refined in the intermediate range, that is, for 1 ≤ Ω < 5. For Ω close to 1, a typical reflective profile is obtained. Terraces are obtained for the Ω = 2.5 cases. For Ω ≈ 3.7, the profiles exhibit two parts: a mild dissipative offshore slope producing low reflection and a steeper beach face with slightly higher reflection. The wave dissipation, velocity skewness, and acceleration skewness are computed from the free surface elevation time series. The dissipation and wave nonlinearities patterns are similar for similar equilibrium beach profiles, that is, with the same Dean number. Dissipation peaks coincide with bottom slope transitions as higher energy dissipation occurs with milder bottom slope sections. Besides, the uniformity of volumetric wave energy dissipation seems to concern only a limited zone of beaches with a widely developed surf zone.

Equilibrium Beach Profile Concept for Delaware Beaches

We utilize beach profile data from 37 profile locations on the Atlantic coast of Delaware that were surveyed an average of 12 times between 1964 and 1993 to assess the validity of several equilibrium beach profile (EBP) formulations. Under consideration are (1) a power law formulation; (2) a formulation including the effects of downslope transport; and (3) a modified form of the latter model suggested herein. We perform a least-square fit of these models to the individual observed profiles, the mean profiles at the 37 locations, as well as regionally averaged profiles over eight geographically distinct regions. The analysis results in best-fit values for the model coefficients. The results indicate that the first model is robust and predicts observed mean and regionally averaged profiles with an estimated normalized error of 26 and 15%, respectively. However, the predicted beach slopes near the shoreline are infinite and, hence, unphysical. The second model includes the effects of downslope transport and ...

Review of Coastal Processes with Engineering Applications by Robert G. Dean and Robert A. Dalrymple

Being a specialist in wave dynamics, I was a little bit surprised to find the names of Professors Dean and Dalrymple as the authors of the new book Coastal Processes with Engineering Applications. Professor Dean as the great developer of the stream function theory and the nonlinear spectral interactions, and Professor Dalrymple as the highly elaborated wave transformation analyst; they are the joint authors of the famous textbook Water Wave Mechanics for Engineers and Scientists. However, my small bewilderment turned out to be a reflection of my ignorance of their innumerable contributions to the study of coastal processes, as I learned by reading this book. The present review is a report of my learning of coastal processes with this book rather than a critical review by a peer in the field of littoral transport and beach morphology. Professor Dean is the promoter of the equilibrium beach profile concept, which refers to a mean equilibrium defined by averaging beach profiles over a long period. The equilibrium beach profile concept was initially conceived and proposed by Bruun in 1954 and 1962, but Professor Dean expanded the concept by correlating the proportionality parameter with the mean sediment diameter and demonstrated its usefulness with many applications. The equilibrium profile concept is now serving as the indispensable tool of American coastal engineers in analysis, planning, and design of shoreline protection projects. Part III of the Coastal Engineering Manual ~draft! by the U.S. Army Corps of Engineers attests the power of the equilibrium profile concept. Coastal Processes with Engineering Applications comprises four parts. Part I, ‘‘Introduction to Coastal Processes,’’ has three chapters and provides the reader with access to various examples of coastal engineering problems, description of sediment characteristics, and several shoreline planforms such as spits, tombolos, barrier islands, etc. that evolve in the long-term coastal processes. This part is quite readable even for nontechnical people and may serve as a means of communications with them. Part II, ‘‘Hydrodynamics of the Coastal Zone,’’ is made up of two chapters: one on tides and storm surges and another on waves and wave-induced hydrodynamics. This part is a summary of the subject listed above, but a detailed review is given on the lowfrequency motions at the shoreline. Swash zone dynamics is also discussed in detail over six pages, starting from the balance of forces acting on elemental swash particle. Part III, ‘‘Coastal Responses,’’ is the core of this book, covering 210 pages with five chapters. The first chapter in Part III introduces the techniques of field measurements and analysis. The next chapter elaborates the concept of equilibrium beach profiles over 48 pages. Anyone unfamiliar with this concept can gain a good idea of this concept and its applications by studying this chapter. The third chapter discusses the longshore and cross-shore