Coastal Erosion Problems Research Articles

Shoreline Change Analysis using Airborne LiDAR Bathymetry for Coastal Monitoring

ABSTRACT Kim, H.; Lee, S.B., and Min, K.S., 2017. Shoreline change analysis using airborne LiDAR bathymetry for coastal monitoring. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 269–273. Coconut Creek (Florida), ISSN 0749-0208. Shoreline is commonly defined as the boundary between land and sea. As a consequence of global climate changes and human interventions, shoreline is constantly changing by erosion and accretion. Korea is also faced with the coastal erosion problem. Therefore, the coastal monitoring method needs to quantitatively analyze the shoreline locations and differences in past and present. For this, our research for coastal monitoring is to adopt the quantitative analysis of shoreline change using airborne bathymetry LiDAR. Bathymetry data is useful for coastal monitoring, since the water depth provide geospatial information of 3D point cloud data, including the sha...

Considering the locals: coastal construction and destruction in times of climate change on Anjouan, Comoros

The current discussion of anticipated climate change impacts and future sea level rise is particularly relevant to small island states. An increase in natural hazards, such as floods and storm waves, is likely to have a devastating impact on small islands' coastlines, severely affecting targeted sustainable development. Coastal erosion, notably human‐induced erosion, has been an ongoing threat to small island biodiversity, resources, infrastructure, and settlements, as well as society at large. In the context of climate change, the problem of coastal erosion and the debate surrounding it is gaining momentum. Before attributing associated impacts to climate change, current human activities need to be analysed, focusing not only on geomorphological and climatological aspects, but also on political and traditional cultural frameworks. The objective of this paper is to demonstrate the importance of the social‐political‐ecological systems analysis for adaptation strategies, and thus for future sustainable development. Coastal use is based on human constructs of the coast, as well as local perceptions and values ascribed to the coast. We use the case study of Anjouan, Comoros to differentiate between constructive and destructive practices on the coast, from both a mental and technical perspective. Beach erosion is described as more than a resource problem that manifests itself locally rather than nationally. Divergent political scales of interest impact future development as much as local action. Local action is not least framed by mental contribution and attribution of coasts as places for living, recreation and resource use. The present case study demonstrates that mental constructs of coasts as valuable areas can, in some cases, lead to the protection and preservation of beaches by initiatives of collective action. At the same time, local communities see the negative impacts of sand mining as causes of coastal erosion and, therefore, it is difficult to mobilize them to adapt to climate change and sea level rise.

A combined DPSIR and SAF approach for the adaptive management of beach erosion in Monte Hermoso and Pehuen Co (Argentina)

Coastal areas experience multiple pressures from anthropogenic activities that negatively change the ecological and environmental status of beaches and impact human welfare. The focus of this paper is coastal erosion, an issue that is very relevant for Argentina, the second largest nation in Latin America with an extensive coastline of nearly 5000 km. Coastal erosion decreases the attractiveness of coastal areas for tourism development, leading to considerable economic impacts. In this paper, two complementary approaches, the Driver-Pressure-State-Impact-Response (DPSIR) and the Systems Approach Framework (SAF), were used to analyse two beach resorts in Argentina: Monte Hermoso and Pehuen Co. Application of the SAF included stakeholder mapping, governance (institutional) mapping and issue identification. During the participatory meetings with stakeholders and decision makers, the problem of coastal erosion was identified as the most important in the region. The joint approach of DPSIR and SAF contributed to: (i) the determination and description of the economic drivers of coastal erosion; (ii) the identification of the associated activities and pressures; (iii) the assessment of the ecological and environmental state of coastal areas; (iv) the assessment of impacts of environmental changes on human wellbeing; and finally (v) a proposal of the possible management responses for mitigating the coastal erosion problem and the sustainable development of the region to the responsible authorities.

Coastal erosion problem, modelling and protection

Goksu Delta, located in the south of Silifke County of Mersin on the coastal plain formed by Goksu River, is one of the Specially Protected Areas in Turkey. Along the coastal area of the Delta, coastline changes at significant rates are observed, concentrating especially at four regions; headland of Incekum, coast of Paradeniz Lagoon, river mouth of Goksu and coast of Altinkum. The coast of Paradeniz Lagoon is suffering significantly from erosion and the consequent coastal retreating problem. Therefore, the narrow barrier beach which separates Paradeniz Lagoon from the Mediterranean Sea is getting narrower, creating a risk of uniting with the sea, thus causing the disappearance of the Lagoon. The aim of this study was to understand the coastal transport processes along the coastal area of Goksu Delta to determine the coastal sediment transport rates, and accordingly, to propose solutions to prevent the loss of coastal lands in the Delta. To this end, field measurements of currents and sediment grain sizes were carried out, and wind climate, wave climate, circulation patterns and longshore sediment transport rates were numerically modeled by HYDROTAM-3D, which is a three dimensional hydrodynamic transport model. Finally, considering its special importance as an environmentally protected region, some coastal structures of gabions were proposed as solutions against the coastal erosion problems of the Delta. The effects of proposed structures on future coastline changes were also modeled, and the coastlines predicted for the year 2017 are presented and discussed in the paper.

Coastal protection measures, case study (Mediterranean zone, Egypt)

The rapid erosion in most coastlines is considered a major problem not only in Egypt, but also around the world. The main causes are due to anthropogenic activities and/or coastal hydrodynamics. The coastal zone suffers from sedimentation, accretion, and pollution problems as well as the side effect of climate change. The climate change will increase sea level rise, salt water intrusions, and storm surge. Major efforts has been exerted to manage coastal erosion problems and to restore coastal capacity in order to protect housing, infrastructure and the cultivated land. These problems were encountered with various types of hard structures, but most of these methods response were limited due to lack in evaluation of the entire ecological situation. This encouraged the coastal engineers to think about new types of environmental friendly structures work better with ecological situation. In this study, the protection measures worldwide is reviewed and divided mainly into four groups, hard, soft, combined, innovative measures. The usage and side effect of each type is mentioned briefly. It is clear that there is a predominant approach towards the soft engineering, the eco-engineering techniques, or combination between them in order to enhance the ecological situation. Recently, there are several efforts to apply these new technologies to protect the coastal zone as well as the environment by taking into consideration the effect of climate change. These new approaches in coastal protection are multi used, environmentally friendly, easy to modify and maintain, and efficient from an economic perspective. Previous efforts in solving coastal problems in Egypt are analyzed and discussed taking into consideration the experience of similar cases worldwide. It is clear that the environmental friendly coastal structure is more suitable to solve most of our coastal problems with saving our ecosystem and reduce the protection cost.

Siltation and Coastal Erosion at Shoreline Harbours

One of the major maintenance problems encountered by the shoreline harbours along east coast of India is siltation of approach channels due to huge longshore sediment movement by wave action along the coast. Wave induced longshore sediment transport rates along east coast of India at selected major shoreline harbours Chennai, Visakhapatnam and Paradip have been estimated using an energy flux method. The direction of littoral drift is generally from south to north during the period March to October when southwest monsoon blows over Bay of Bengal and reverses its direction from north to south during the period November to February during northeast monsoon season. The rates of sediment transport however vary from one shoreline harbour to another depending upon the wave climate and other near shore features. While the littoral drift rates are high during south west monsoon season from March to October at Visakhapatnam and Paradip harbours, the Chennai harbour on the other hand experiences high rates of littoral drifts during north east monsoon months particularly from November to January due to storm waves along the coast. The estimated sediment transport rates have been compared with the available dredging quantities to know their accuracies. The problems of siltation and coastal erosion have become severe over the years due to deepening of the harbour channels as a part of expansion and modernization of ports. Hence, a detailed study on siltation problems faced by the shoreline harbours will definitely useful not only for dredging management plan for existing ports but also for planning new port locations along the coast. The historical problems of the shoreline harbours due to construction of harbour installations at selected important ports along east coast of India have been discussed briefly.

Beach Profile Changes Due to Low Crested Breakwaters at Sigandu Beach, Central Java

Sigandu is a coastal tourism area, which is located in the coastal zone of Batang District. Central Java Province. This coastal area faces severe coastal erosion problem. It is indicated that erosion processes are occurred due to the jetty construction of Batang Commercial Port. This construction cause disturbance of longshore transport equilibrium. The objective of jetty construction is to trap the sediment, however, the classical problem of erosion and accration take place in a short time, soon after the jetty construction finished. The local government of Batang District becomes aware because of this erosion problem. Commenced on September 2014, the Marine and Fisheries Affair initiates the solution by applying low-crested breakwaters structures using geotextile tube. One month after the tube installation, rapid sedimentation occurred by the formation of salients and tombolos behind the structures. Beach profile calculation have been carried out through the series of monitoring and cross section measurement as well as visual observation. This paper presents results of monitoring beach activities. The case study is expected to be an example and applied for other coastal areas having similar coastal problems.

Shoreline Response to Coastal Structures

The coastal erosion has become a critical problem for states which are facing acute shortage of land due to high density of population and narrow width available for the state. With this in mind, different protection methods have been used over time, most on the basis of the artificial nourishment of beaches and building coastal structures such as groins and detached breakwaters. The decision to build a coastal structure should be based on a thorough analysis of the shoreline developments in the past and estimated developments in the future. The physical processes causing erosion should be properly identified, otherwise erroneous decisions may be taken. In the present paper an attempt is made to design series of groins and series of detached breakwaters for shore protection taking into account both alongshore sediment transport and cross-shore sediment transport. A mathematical model was used, which takes into account wave parameters, detached breakwater configuration, groins configurations, initial shoreline and bathymetry as input and provides shoreline changes. Shoreline response was obtained by varying various parameters of detached breakwaters and groins, such as detached distance of breakwaters, gap width between the breakwaters, width of breakwater, length of groins, gap width between groins and length of groins. With detached breakwaters it was seen that coastline is subjected to less erosion as compared to the groins because detached breakwater does not block the littoral drift completely and allows passage of some drift material. Therefore detached breakwaters used in combination with beach nourishment offer a better and environmentally suitable solution to combat coastal erosion problems.

Rip Current Monitoring Using Video Analysis

Shin, B.S. and Kim, K.H., 2014. Rip current monitoring using video analysis.The coast of South Korea is increasingly exposed to serious coastal erosion problems. It is vital to develop scientific and systematic approaches for a quantitative review of the problem so that appropriate countermeasures can be established. Recently, a research method employing video images has become significant in field investigation and real-time monitoring. The proposed approach of this study is to measure the sea surface rather than to measure specific sea spots. Using the collected video images, each images are extracted an hourly basis in a specific time zone. Also, the extracted images are calibrated using geometrics and then the mechanism of wave-induced current occurrence and its moving path are investigated. Using dyes, the flow conditions of wave-induced current were filmed on a regular basis. As a result, the paths of longshore current and strong rip current were found. It is expected that the Video Metric System employed in this study will be effectively utilized in field tests in near future to further study the mechanism of wave induced current occurrence and its paths.

LONG-TERM SEDIMENT TRANSPORT IN KUZURYU RIVER AND KAETSU COAST UNDER HOLOCENE SEA LEVEL VARIATION

The Kaetsu Coast has been facing problems of coastal erosion and accumulation of sediments in dams and harbors. This study aims to investigate sediment transport and its long-term changes considering sea level variation in the Holocene. Numerical calculation of waves and nearshore currents, together with analysis of physical properties of sand particles such as diameter, color and thermo-luminescence were conducted to estimate the source and transport direction of sediment over geological time scale. It is found that the changes in the nearshore currents around the Kuzuryu River mouth and sediment supply from old dunes onto the coast north of the Kuzuryu River mouth are essential in understanding the sediment movement in the watershed scale.

TEMPORAL SHORELINE SERIES ANALYSIS USING GNSS

In recent decades, Boa Viagem beach located in the city of Recife-PE and Piedade in Jaboatão dos Guararapes-PE (Brazil) has seen urbanization near the coastline causing changes in social, economic and morphological aspects, where coastal erosion problems are observed. This study uses GNSS (global navigation satellite system) shoreline monitoring approach, which is quicker, and provides continuously updatable data at cm-level accuracy to analyze and determine temporal positional shifts of the shoreline as well as annual average rates through EPR (end point rate). To achieve this, kinematic GNSS survey data for the years 2007, 2009, 2010 and 2012 were used. The results show sectorial trends over the years, with the highest annual retreat rate of 8.16 m /year occurring during the period 2007-2009. Variety of differents patterns over the shoreline was also observed. These findings could be essential for decision making in coastal environments.

Sediment Characteristics of an Impacted Coastal Bay: Baía de Guanabara, Rio de Janeiro, Brazil

Araruna Júnior, J.T.; de Campos, T.M.P., and Pires, P.J.M., 2014. Sediment characteristiscs of an impacted coastal bay: Baía de Guanabara, Rio de Janeiro, Brazil.Baía de Guanabara is one of the largest and most important bays of the Brazilian coastline. Over recent years coastal erosion problems have been registered there, mainly due to increasing urbanization and industrial development related to the oil and gas industry. This paper presents the results of an experimental program aimed at obtaining the rheological and sedimentation properties of the sediments that are on the pipeline routes in the bay. With this information it is possible to assist the municipality in reducing beach erosion and implementing sustainable measures for better coastal development. It was found that the sediments from Baía de Guanabara have sedimentation rates ranging from 0.63 to 13.25 cm/min. Solid content is relatively low, consistent with the fact that they are unconsolidated sediments. The particle size distribution of the sediments reflects the depth of the water column of Baía de Guanabara; the deeper the water column, the coarser the sediment. However, the sediment shows plasticity, suggesting the presence of organic matter derived from the 20 m3s−1 raw sewage discharged into the bay. Fine sediments are found near shore; these are fluvial in origin or come from diffuse pollution sources. Their activity is high, indicating that it might be correlated to the presence of clay minerals. Regarding physical indices, it was found that the finer sediments have higher water contents and porosities but lower particle densities; total and dry. The coarser sediments present grains of spheroidal format, composed mainly of quartz, feldspar and amethyst.

Behind the increasing erosion problem: The role of local institutions and social capital on coastal management in Argentina

Coastal ecosystems are one of the most impacted and altered regions worldwide, both because of natural reasons and because of the large population that is concentrated along the coasts. In Argentina, the problem of coastal erosion is very important as these areas represent the 18.33% of the whole territory with 36% of population living in this area. The objective of the present article is to characterize the main problems related to the use of resources and coastal management, leading to coastal erosion, from the perceptions of stakeholders and decision makers in the coastal zone of Pehuén Co and Monte Hermoso, Argentina. The fieldwork was performed by participative methodologies, while the results were analyzed under the institutional and social capital theoretical framework. One of the main results of the paper is that the lack of a strong social capital in the region and the existence of formal monitoring and sanctioning procedures developed by distant governmental institutions have increased the overexploitation of coast and beaches. Notwithstanding, the current and future relevance of coastal erosion for the region will demand the elaboration of bottom-up policies to reduce the vulnerability of the region and the performance of the adaptation policies.

Comparison of observation and laboratory slaking tests in the assessment of coastal erosion in Cheju Island, Korea

This study reports on the main problems of coastal erosion around Cheju Island, Korea. Field surveys showed that main causes of severe cliff erosion is the differential weathering of geological strata, for instance, alternating bands of durable sandstone and less durable shale. Experimental work showed that such durability against coastal erosion can be expressed in terms of slake durability. It is suggested that the slake durability test is a good tool for the quantitative assessment of the sensitivity of rock to coastal erosion.

The Impact of Makeshift Sandbag Groynes on Coastal Geomorphology: A Case Study at Columbus Bay, Trinidad

Coastal erosion threatens coastal land which is an invaluable limited resource to Small Island Developing States (SIDS). Columbus Bay, located on the south-western peninsula of Trinidad, experiences high rates of coastal erosion which has resulted in the loss of millions of dollars to coconut estate owners. Owing to this, three makeshift sandbag groynes were installed in the northern region of Columbus Bay to arrest the coastal erosion problem. Beach profiles were conducted at eight stations from October 2009 to April 2011 to determine the change in beach widths and beach volumes along the bay. Beach width and volume changes were determined from the baseline in October 2009. Additionally, a generalized shoreline response model (GENESIS) was applied to Columbus Bay and simulated a 4 year model run. Results indicate that there was an increase in beach width and volume at five stations located within or adjacent to the groyne field. The GENESIS model confirmed accretion within the groyne field and indicated a reduction in transport rates between groynes when compared to the rest of the bay to within 77.56 % accuracy. This study revealed that the makeshift groynes though improperly engineered, has reduced coastal erosion by encouraging accretion. The GENESIS model can be a helpful tool to inform management decisions at Columbus Bay and other beaches and bays inTrinidad and Tobago.

Two-Dimensional Depth-Averaged Beach Evolution Modeling: Case Study of the Kızılırmak River Mouth, Turkey

This study presents an application of a two-dimensional beach evolution model to a shoreline change problem at the Kızılırmak River mouth, which has been facing severe coastal erosion problems for more than 20 years. The shoreline changes at the Kızılırmak River mouth have been thus far investigated by satellite images, physical model tests, and one-dimensional numerical models. The current study uses a two-dimensional depth-averaged numerical beach evolution model, developed based on existing methodologies. This model is mainly composed of four main submodels: a phase-averaged spectral wave transformation model, a two-dimensional depth-averaged numerical wave-induced circulation model, a sediment transport model, and a bottom evolution model. To validate and verify the numerical model, it is applied to several cases of laboratory experiments. Later, the model is applied to a shoreline change problem at the groin field to the east of the Kızılırmak River mouth at the Bafra alluvial plain. The results of the numerical model agree with the existing laboratory and field measurements.

An Ensemble of Geostatistical Simulated Realizations Using a Clustering Algorithm to Reproduce Model-Based Statistics: Case Study of a Gravel Reserve at Kivalina, Alaska

This paper demonstrates the convergence of model-based statistics from multiple simulated realizations. Theoretically, the convergence of realization statistics is guaranteed over the number of realizations that are independent among themselves. The rate at which realization-based statistics converges with model-based statistics is important and must be assessed. However, due to poor selection of the random number generator, the generated realization might be far from mutual independence. We use the k-means clustering algorithm to select nearly independent realizations from a set of realization models. We apply the proposed algorithm to a coastal erosion problem in Alaska to estimate the amount of gravel.

Sensitivity analysis of the methodology for quantifying cliff erosion using airborne LiDAR – examples from Cornwall, UK.

Earlie, C.S., Masselink, G., Russell, P.A., and Shail, R.K., 2013. Sensitivity analysis of the methodology for quantifying cliff erosion using airborne LiDAR – examples from Cornwall, UK.The widespread problem of coastal cliff erosion and the management of the risk to infrastructure and property calls for robust quantification of cliff erosion rates. Quantification of sea-cliff rates of retreat on an annual to decadal time scale has typically been limited to rapidly eroding soft rock coastlines. This study uses airborne LiDAR technology to estimate cliff volume changes in hard rock environments to determine linear retreat rates. One epoch of LiDAR data was analysed (2007/2008–2010/2011) for ten sites around the coast of the southwest of England (Cornwall), selected due to the spatial variability in regional morphological processes, lithology and wave climate. Quantifying cliff recession rates using two LiDAR-derived Digital Elevation Models (DEM) requires selection of an elevation change threshold, below which the morphology is assumed to have undergone no significant change, referred to as the ‘vertical change threshold'. The errors inherent in using LiDAR and the various thresholds at which the data could be evaluated were tested. Linear rates of retreat were found to vary according to the threshold of error chosen, providing decreasing rates with an increase in threshold above 0.2–0.3 m. The rates of retreat observed at some low energy sites was of the same magnitude and in some cases lower (0.01–0.03 m yr−1) than the threshold of error inherent in the LiDAR data (0.03–0.1 m). The results were compared with the rates of retreat obtained from analysis of historic maps in Shoreline Management Plans which are non-statutory strategic assessments of the risks associated with coastal erosion that ultimately inform local and regional policy. Analysis of coastal erosion using LiDAR data tended to highlight the localised failures that occur episodically and which are averaged out in the rates derived from longer term analysis of historic maps.

The role of sediment characterization in environmental studies to assess the effect of relict sand dredging for beach nourishment: the example of offshore sand deposits in Lazio (Tyrrhenian Sea)

Paganelli D., Nonnis O., Finoia M.G. and Gabellini M., 2013. The role of sediment characterization in environmental studies to assess the effect of relict sand dredging for beach nourishment: the example of offshore sand deposits in Lazio (Tyrrhenian Sea) In: Conley, D.C., Masselink, G., Russell, P.E. and O’Hare, T.J. (eds.), Proceedings 12 th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 10151020, ISSN 0749-0208. Beach nourishment with relict sands has been carried out for several years as a way to counter coastal erosion problems, and it has proven to be a successful beach protection method and one of the most important coastal management tools available. It is however known that relict sand dredging may have significant physical and biological effects on the marine environment, especially in highly biodiverse environments and sensitive habitats such as the Mediterranean marine and coastal system. Within this framework, the Regione Lazio (Italy) local Authority has financed and implemented some research projects aimed at identifying marine sand deposits along the Latium continental shelf. The research brought to the identification of five areas suitable for the exploitation of relict sands along the Tyrrhenian continental shelf. ISPRA was commissioned to carry out environmental characterization studies to evaluate the effects of dredging nourishment-aimed relict sand on the marine environment. This paper presents the results of the grain-size characterization study carried out in the areas identified as suitable for dredging of relict sands; the study allows the identification of the main sedimentological features of the investigated areas, providing some of the necessary information to assess the potential environmental effects of relict sand dredging.

海水準変動を踏まえた九頭竜川・加越海岸流砂系における土砂移動実態の解明

Kaetsu region has been facing problems of coastal erosion and accumulation of sediments in dams and harbors. This study aims to investigate sediment transport and its long-term changes considering sea level variation. Numerical calculation of waves and nearshore currents, together with analysis of physical properties of sand particles such as thermoluminessence, color and size were conducted to estimate the source and transport direction of sediment over geological time scale. It is found that the changes in the nearshore currents around the Kuzuryu River mouth and sediment supply from old dunes onto the coast north of the Kuzuryu River mouth are essential in understanding the sediment movement in the watershed scale.