Shore Protection Research Articles

Transect based analysis versus area based analysis to quantify shoreline displacement: spatial resolution issues.

Field surveys, aerial photographs, and satellite images are the most commonly employed sources of data to analyze shoreline position, which are further compared by area based analysis (ABA) or transect based analysis (TBA) methods. The former is performed by computing the mean shoreline displacement for the identified coastal segments, i.e., dividing the beach area variation by the segment length; the latter is based on the measurement of the distance between each shoreline at set points along transects. The present study compares, by means of GIS tools, the ABA and TBA methods by computing shoreline displacements recorded on two stretches of the Tuscany coast (Italy): the beaches of Punta Ala, a linear coast without shore protection structures, and the one at Follonica, which is irregular due to the presence of groins and detached breakwaters. Surveys were carried out using a differential global positioning system (DGPS) in RTK mode. For each site, a 4800-m-long coastal segment was analyzed and divided into ninety-six 50-m-long sectors for which changes were computed using both the ABA and TBA methods. Sectors were progressively joined to have a length of 100, 200, 400, and 800m to examine how this influenced results. ABA and TBA results are highly correlated for transect distance and sector length up to 100m at both investigated locations. If longer transects are considered, the two methods still produce good correlated data on the smooth shoreline (i.e. at Punta Ala), but correlation became significantly lower on the irregular shoreline (i.e., at Follonica).

Economic evaluation of using marine dredged material for erosion control along the northeast coast of the Nile Delta, Egypt

The present study is the first attempt in Egypt to assess feasibility of using of dredging material from Damietta Harbor in the northwestern Nile Delta for erosion control. The study also provides an economic evaluation for the shoreline management alternatives selected to mitigate for the effects of coastal erosion at two pilot eroding areas (namely, A and B) located near the Damietta Harbor. Results of compatibility analysis reveal that the dredging material is fairly compatible with the native sand of the nearby eroding beaches. In addition to soft nourishment by dredged sand, other types of coastal engineering measures which are often used in erosion management area were also evaluated as alternatives for erosion control and mitigation solution. Economic feasibility assessment by means of cost-benefit analysis of direct and indirect items has been carried out to facilitate comparison between these alternatives. Analysis of alternatives has been also supported by other criteria to select the cost-effective and environmentally acceptable option to protect the eroding pilot areas. These criteria include the high total cost paid for maintenance of the Damietta Harbor channel with no use, anticipated impacts on the littoral system, sustainability, future plans for protection of the existing coastlines, and lessons learned from previous shore protection works in the Nile Delta. The final selection of the best viable alternative indicates that the procedure of beach nourishment is the most appropriate form for protection area A, while a combination of groins and sand nourishment is more relevant for area B. In any case, material dredged from the navigation approach of the Damietta Harbor should be utilized as a borrow material in the nourishment schemes and excluding use of the terrestrial sources.

Parameterization of Maximum Significant Wave Heights in Coastal Regions due to Hurricanes

AbstractA method for expedient characterization of maximum nearshore wave heights due to hurricanes is described. This method, referred to as the wave response function (WRF) method, relates hurricane parameters to maximum wave heights by fitting coefficients from the modified Shore Protection Manual (SPM) forecasting method to results from numerical surge-wave models. The method was applied to numerous locations along the U.S. Gulf Coast: Corpus Christi, Texas; Gulfport, Mississippi; and Panama City, Florida. The WRF method is shown to have the most skill of all similar methods tested. Similar accuracy levels were obtained across all test sites. Data from Hurricane Ike in 2008 provided validation for the method. Although not intended for forecasting, this approach can be applied to risk analysis and extreme value statistics with significantly less computational effort than the use of numerical models.

Ecological Consequences of Shoreline Hardening: A Meta-Analysis.

Protecting coastal communities has become increasingly important as their populations grow, resulting in increased demand for engineered shore protection and hardening of over 50% of many urban shorelines. Shoreline hardening is recognized to reduce ecosystem services that coastal populations rely on, but the amount of hardened coastline continues to grow in many ecologically important coastal regions. Therefore, to inform future management decisions, we conducted a meta-analysis of studies comparing the ecosystem services of biodiversity (richness or diversity) and habitat provisioning (organism abundance) along shorelines with versus without engineered-shore structures. Seawalls supported 23% lower biodiversity and 45% fewer organisms than natural shorelines. In contrast, biodiversity and abundance supported by riprap or breakwater shorelines were not different from natural shorelines; however, effect sizes were highly heterogeneous across organism groups and studies. As coastal development increases, the type and location of shoreline hardening could greatly affect the habitat value and functioning of nearshore ecosystems.

Facilitating landform migration by removing shore protection structures: Opportunities and constraints

Recent studies have identified the need to adapt to climate change by allowing landforms and habitats to migrate landward, although implementation of actual adaptation responses is limited. Removing the barriers that shore protection structures create between coastal and upland habitats can reestablish exchanges of sediment and the ecological functions of the natural ecotone. The potential for removing these structures was evaluated in 12 national parks managed by the U.S. National Park Service. Criteria for removal included condition of structures, influence of natural processes, environmental benefits, public safety, and visitor access and use.We found that 145 structures out of a total of 407 could be removed or allowed to deteriorate. We highlight three adaptation projects that are currently being conducted, two of which involve removing structures. Reasons for not taking a more pro-active approach to removing protection structures include (1) conflicting policy directives; (2) presence of key access roads and critical archaeological and historic sites; (3) lack of data; (4) lack of funds and human resources; (5) reluctance to replace known problems with an unknown set of problems; (6) consideration of visitor desires; and (7) reluctance to allow erosion to occur. Demonstration projects are needed to provide information about adaptation strategies that promote enhancement of ecosystem functions. Projects to remove protection structures are likely to be viewed as successful only if results are specified as a positive product, and the distinction between the concept of loss (erosion of existing landforms and habitats) and the concept of gain (evolution of new landforms and habitats) is made clear.

Shore protection for the coast of Mousuni Island in West Bengal, India

The Mousuni Island in West Bengal, India is wide-open to Bay of Bengal. This island by virtue of its location is exposed to river flow as well as wave action. It is thus subjected to severe erosion along its south-western coastal stretch and also significantly affecting agriculture due to seawater inundation. This is due to the lower level of bund crest elevation combined with high water levels during coastal flooding. The most suitable method to arrest the shore erosion and salt water intrusion is to divert the flow gradually toward the deeper section of the channel. To meet this requirement, after carrying out a comprehensive profiling of the existing bund, bank connected series of spurs with locally available construction materials and unskilled labor are proposed. In order to design these spurs, the magnitude and direction of sediment movement along the stretch is estimated. The layout of protection measures is proposed based on a detailed analysis of site conditions and the environmental conditions. The tranquility inside the proposed coastal protecting structure is substantiated with a two-dimensional horizontal flow model. Furthermore, the behavior of the shorelines has been studied numerically with the proposed coastal protection measure. The detailed analysis of the results from the numerical model and the protection measure are discussed in this article.

Practical application of life-cycle management system for shore protection facilities

Shore protection facilities have a long lifetime and must be expected to meet demands for providing people living coastlines with safety and security. The principal demands for those facilities seem to be simple but have not been practically so easy to be kept over the requirements. The reasons for those are that facilities are rather big and are exposed to severe environments for materials. Those facts may cause difficulties in even visual inspection. In addition, as it would be very important, rise of the seawater level, etc. due to global warming may affect the function and performance, which has to be taken into account rehabilitation planning. To overcome such difficulties, it is important to pursue coordination between design and maintenance based on the procedure of the life-cycle management through which sustainability indicators would be maximum/minimum. This paper presents the concept and the framework of the life-cycle management system for those facilities and introduces methodologies of the management system particularly feasible to practical maintenance.

Erosion and heavy mineral depletion of a placer mining beach along the south-west coast of India: part III—short- and long-term morphological changes

The Chavara coast of south-west India is well known for its rich beach placer deposits which are being commercially mined by two public sector firms. The erosion of the beach and innershelf and the depletion of heavy mineral content of this coast have attracted a lot of attention of late, and an investigation of the mechanisms that drive these changes was taken up recently. The results of the investigation are presented in three parts. This paper, which is the last in the series, presents a study of the morphological changes of the beach and innershelf and integrates the results from the other two papers with an analysis of multi-dated shoreline and bathymetry data. The analysis of the multi-dated data showed an overall retreat of the shoreline and a relative deepening of the innershelf. The shoreline retreat has been quite alarming at the mining sites with one of the mining sites showing a retreat of nearly 400 m. The sediment deposition adjacent to the breakwater (built during 2000–2007) at the northern inlet has defused to some extent the high erosion observed earlier in the northernmost sector, and the presence of well-maintained seawalls has nearly maintained the shoreline south of the mining site. The erosion of the beach is accompanied by a deepening of the innershelf which is more pronounced in the shallower portions up to 10 m depth. The observed changes in the beach–innershelf morphology are analysed with respect to the nearshore sediment transport regime and heavy mineral distribution of the coast. It is observed that the combined intake of sediments by the two firms during the past one and a half decade is much above the sustainable mining level. Another contributing factor is the 2004 tsunami which drained off a sizable quantity of innershelf sediments rich in heavy minerals to the hinterland regions. The breakwaters at the two inlets bordering this coast have virtually compartmentalized this coast from the rest of the south-west coast making it a sediment sub-cell. In addition, the breakwaters act as groins causing imbalances in the erosion/accretion pattern. The recent spate in construction of shore protection structures like groins and seawalls is another contributing factor to the morphological changes. The study points to the urgent need for regulating the mining volumes to the sustainable levels as well as controlling the introduction of hard structures without proper impact analysis.

Wave atlas for Swiss lakes: modeling design waves in mountainous lakes

The present study aims to provide a comprehensive wave atlas for Swiss lakes. The atlas is an adequate tool that contains wave characteristics of extreme events derived from numerical calculations. Swiss lakes are surrounded by mountains, and the wind field over the lakes is highly influenced by the region’s topography. Therefore, it is important to apply the winds with appropriate direction distribution. The numerical weather prediction model COSMO-2 is used for defining the wind directional distribution, whereas the spectral wave model SWAN is used for wave simulations. The evaluation results are ultimately published on a geographical information internet platform, where a wave rose correlates the wave height to the event frequency for each point on a lake. An accurate knowledge of wave parameters is essential for the design of new shore protection measures, beach erosion control and harbor silting studies.

Present-day use of an empirical wave prediction method

Knowledge of the offshore wave climate is key to the design of coastal engineering structures and to the study of shoreline evolution. To date, the available wave data have been limited both in time and space; even though there are several options for obtaining wave data calculated using complex numerical models at basin scale, design issues can in some cases be solved by means of simpler models. This paper shows whether, under certain conditions and in an enclosed basin, an old empirical model can provide results that are good enough to determine the design condition necessary for engineering purposes. The empirical model chosen to answer this question is called Sverdrup–Munk–Bretschneider modified (SMB-X) and was developed based on the indications of the Shore Protection Manual. The model was applied to an area off the northern coast of Sicily (Italy). The results were compared with measurements from a wave buoy. To evaluate whether the model is an efficient tool to calculate the ‘design wave’, a statistical analysis of extreme events is necessary. Such an analysis was performed on the measured wave parameters, on the wave parameters calculated by the empirical model and on those calculated by two spectral models that are as easy to use as the SMB-X.

Cyclone and monsoonal wave characteristics of northwestern Bay of Bengal: long-term observations and modeling

Long-term wave data play a crucial role in arriving the wave criteria for ports and harbors and shore protection structures. Seasonal and annual wave characteristics are studied based on wave data collected for the year 1994, 2008–2009 and 2013–2014 off Gopalpur, northwestern Bay of Bengal (BoB). The tropical cyclones ensued in BoB hit the coast frequently causing severe erosion due to extreme waves. The sea and swell waves are separated by wave steepness method, and the significant wave height (H s), zero-crossing period and mean wave direction are examined. The results indicate a distinct shift in sea direction by 90° during mid-November to mid-February compared with rest of the year. Throughout the year, predominant swell direction is 160°. In an annual cycle, the contribution of swells in wave height is slightly higher than that of the seas. Annual occurrences of single-, double- and multi-peaked spectra are 22, 40 and 38 %, respectively. The waves are predominant southerly during the southwest monsoon (June, July, August and September) and south-southeasterly for rest of the year, and the variations of wave parameters for three different years are trivial. The spectral wave model MIKE 21 is used to simulate wave characteristics using reanalyzed NCEP wind data for the period June 2008 to May 2009 which exhibits good agreement with a correlation coefficient (R) of 0.86 for H s. The design significant wave height of 7.1 m and 7.8 m is calculated for 10 and 100 years of return periods, respectively, by Weibull distribution.

Numerical simulations of wave propagation over a vegetated platform

Vegetated platforms have been constructed in recent years for the purpose of shore protection. This paper addresses some fundamental questions concerning the vegetated platform: (1) What is the difference in wave attenuation between a vegetated platform and a simple platform, and how much can vegetation increase the efficiency of reducing wave transmission? (2) Are there any differences between the effects of stems and roots on wave attenuation? (3) Does vegetation always reduce wave transmission? (4) Is it possible to develop an empirical formula for estimating the wave transmission of a vegetated platform? To answer the above questions, a numerical model solving the Navier–Stokes equations for wave propagation over a vegetated platform is established and validated by several existing laboratory experiments. A total of 244 numerical experiments based on this model have been carried out. The simulated results suggest that the platform plays a major role and the vegetation plays a supporting role in reducing wave transmission except for some special cases. Stems tend to have a larger influence than roots in reducing wave transmission with the same height. The roots always help reduce wave transmission, while the stems may increase wave transmission when the platform width is in the range of 37.5–62.5% of the incident wavelength. Based on our numerical experiments and existing laboratory data, the paper proposes a simple formula for predicting the wave transmission coefficient of a vegetated platform for engineering applications.

Relationship between high-frequency sediment-level oscillations in the swash zone and inner surf zone wave characteristics under calm wave conditions

AbstractSwash zone topography rapidly responds to the surf zone waves. Understanding how sandy beaches respond to wave action is critical for beach erosion research, and plays a critical role in the design and maintenance of shore protection structures. The main objectives of this study were to detect the relationship between high-frequency beachface oscillations and surf zone wave characteristics under plunging breakers by using Canonical Correlation Analysis (CCA). The study site is located in Houjiangwan Bay, eastern Guangdong. Topography data were sampled at 6 min intervals. The wave characteristic parameters were calculated by spectrum method. During the field work, the beach showed a reflective state and plunging breakers controlled the surf zone. The beach cusp topography was destructed gradually. The analysis provides 4 canonical correlation processes between the beachface variations and surf zone waves, which explained 95.28% of the overall variation in the data. The result shows wave steepness, the irregularity factor and spectral broadness factor had strong impacts on the topography. The wave steepness was the most important factor for beach profile variations. The results of the present study indicate that data-driven statistical analysis, such as CCA, is useful for analyzing profile response to waves if there is strong correlation between the two variables (beach profiles and wave).

Determination of Wave Reflection Formulae for Vertical and Sloped Seawalls Via Experimental Modelling

This paper presents and discusses the results of experimental investigations using both vertical and sloping seawalls configurations to determine the optimal wave reflection characteristics of seawalls for protecting beaches against erosion under a variety of hydrodynamic conditions. The different experiments include both of rectangular or triangular serrated blocks and slotted seawalls with or without triangular serrations as energy dissipaters. The linear wave theory is utilized. Moreover, the Dalrymple method is considered to predict the ordinates of the resultant standing wave due to the partial wave reflection. Using the dimensional analysis, lab measurements, and SPSS, predictive formulae are proposed to predict the reflection coefficient for the five tested models by using SPSS software. The findings of the present investigation could be applied to optimize the design criteria of shore protection structures.

Modeling of concrete mattress for shore protection by Plaxis 2D

Modeling of concrete mattress for shore protection by Plaxis 2D

Resilience from coastal protection.

Coastal areas are important residential, commercial and industrial areas; but coastal hazards can pose significant threats to these areas. Shoreline/coastal protection elements, both built structures such as breakwaters, seawalls and revetments, as well as natural features such as beaches, reefs and wetlands, are regular features of a coastal community and are important for community safety and development. These protection structures provide a range of resilience to coastal communities. During and after disasters, they help to minimize damages and support recovery; during non-disaster times, the values from shoreline elements shift from the narrow focus on protection. Most coastal communities have limited land and resources and few can dedicate scarce resources solely for protection. Values from shore protection can and should expand to include environmental, economic and social/cultural values. This paper discusses the key aspects of shoreline protection that influence effective community resilience and protection from disasters. This paper also presents ways that the economic, environmental and social/cultural values of shore protection can be evaluated and quantified. It presents the Coastal Community Hazard Protection Resilience (CCHPR) Index for evaluating the resilience capacity to coastal communities from various protection schemes and demonstrates the use of this Index for an urban beach in San Francisco, CA, USA.

LABORATORY SIMULATIONS OF WAVE ATTENUATION BY AN EMERGENT VEGETATION OF ARTIFICIAL PHRAGMITES AUSTRALIS: AN EXPERIMENTAL STUDY OF AN OPEN-CHANNEL WAVE FLUME

This paper presents a well-controlled laboratory experimental study to evaluate wave attenuation by artificial emergent plants (Phragmites australis) under different wave conditions and plant stem densities. Results showed substantial wave damping under investigated regular and irregular wave conditions and also the different rates of wave height and within canopy wave-induced flows as they travelled through the vegetated field under all tested conditions. The wave height decreased by 6%–25% at the insertion of the vegetation field and towards the downstream at a mean of 0.2 cm and 0.32 cm for regular and irregular waves respectively. The significant wave height along the vegetation field ranged from 0.89–1.76 cm and 0.8–1.28 cm with time mean height of 1.38 cm and 1.11 cm respectively for regular and irregular waves. This patterns as affected by plant density and also location from the leading edge of vegetation is investigated in the study. The wave energy attenuated by plant induced friction was predicted in terms of energy dissipation factor (fe) by Nielsen’s (1992) empirical model. Shear stress as a driving force of particle resuspension and the implication of the wave attenuation on near shore protection from erosion and sedimentation was discussed. The results and findings in this study will advance our understanding of wave attenuation by an emergent vegetation of Phragmites australis, in water system engineering like near shore and bank protection and restoration projects and also be employed for management purposes to reduce resuspension and erosion in shallow lakes.

Marine Ecological Assessment for LNG Terminal at Port Qasim

Multinational companies intend to develop a Liquefied Natural Gas (LNG) terminal with floating storage and regasification arrangement (FSRA) in the jurisdiction of Port Qasim. Approximately 500 MMSCFD or 3.5 million tons per annum of LNG would be transferred through a mooring arrangement, which would require marine works/structures such as a berth for docking and mooring of LNG Carriers and Floating Ship Regasification Arrangement (FSRA) i.e., unloading, storage and vapor recovery and return unit and pipelines to the delivery point for transport to off-takers. The FSRA will deliver the re-gasified liquefied natural gas (RLNG) via jetty and onshore associated facilities to the gas network operated by the in-country transmission pipeline providers SSGCL and SNGPL. The approach channel of Port Qasim is associated with Gharo Phitti Creek System consists of three creeks: Gharo Creek, Kadiro Creek and Phitti Creek has tidal creeks and are with associated mangrove and mudflats ecosystems that are linked with a network of creeks in the Indus Delta. Dredging will be required to create the berthing and the turning basin of diameter 400 to 700 m with a depth of -13.5 m below chart datum (CD). Approximate dredged material would be upto 5.5 Million cubic meters. The dredged material will be utilized for the reclamation and to construct shore protection structure. Land Area of 75-100 acres with water front of 1000 m has been allocated in the PQA for this project. This would be the first time that LNG terminals are being set up in PQA.

Aspects of coastal erosion and protection in Europe

The wide variety of physical, political, economic and cultural attributes along European coasts has led to different national management approaches to coastal protection. In all countries, this became problematic when the coast underwent anthropogenic impact and acquired relevant economic value for uses, such as, transport, military, tourism or conservation. However, common ground technology developed according to each country’s political traditions, technical restrictions and economic viability. This paper outlines the major management aspects of coastal erosion and defence in Europe and discusses the large spectrum of shore protection strategies used. It depicts the current coastal defence scene for 25 European countries, and points to the major trends and challenges faced by coastal managers, land owners and users of European coasts, as coastal management embraces both engineering as well as socio-economic aspects.

Coastal erosion along the Caribbean coast of Colombia: Magnitudes, causes and management

“Sun, Sea and Sand” tourism is one of the fastest increasing activities in Colombia. The coast, specifically the Caribbean coast, represents the favourite destination for national and foreign visitors. However, over the last 30 years while tourism activities increased, coastal erosion became a serious problem rising in magnitude and dominance. This paper deals with a historic overview of Colombian Caribbean coastal erosion, the calculus of associated magnitudes and deepens knowledge and understanding of the different factors that control this process in this location. Coastal change in terms of erosion-sedimentation was determined by comparatives analysis of satellite images for the 1980–2014 period, as well as field surveys. Results showed circa 50% of the Colombian Caribbean coast is undergoing serious erosion. In detail, 48.3% (1182 km) of the investigated coast is experiencing erosion; 33.2% (812.6 km) can be considered stable, and 18.4% (450.5 km) is accreting. Coastal erosion can be associated with a diversity of factors contrasting in their degree of magnitude and influence, such as, amongst others: sedimentary imbalance, extreme waves, ecosystem destruction and sea level rise. These processes are often multiplied by human activities e.g. inappropriate building of coastal infrastructures, e.g. groins, illegal mining of sand and destruction of mangroves. Currently, coastal erosion produces not only beach loss but also deterioration of scenic quality and further significant financial investments for hard shore protection structures (groins and breakwaters, principally). Therefore, coastal erosion has become an obstacle that hinders the economic growth of Colombia. Results obtained can be used in the correct application of coastal management policies in order to preserve socio-economic activities, such tourism. Specifically, stronger management laws in line with Marine Spatial Planning attributes need to be implemented and enforced; more sustainable funding found for legislation and a better support network for decision making with the over riding objective of increased sustainability.