Beach Erosion of Kashimanada Coast and Prediction of Beach Changes
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Abstract:
On the Kashimanada coast, fine sand was selectively transported and deposited in the wave-shelter zone behind the offshore breakwater built on both ends of the coastline, whereas beach was eroded in the central part of the coastline. As a measure, artificial headlands have been constructed on this coast, but beach erosion is still severe. The contour-line-change model considering the effect of changes in grain size was applied to this coast, and the effect of the measure was evaluated. The differences between the total accreted and eroded volumes of sand in the condition with/without headlands became 7.4×106 and 8.1×106 m3. Thus, it was found that the movement of approximately 8.0×106 m3 of sand was controlled by headlands.Keywords:
Breakwater
Coastal erosion
Headland
Beach nourishment
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Since 2011, beach nourishment has become the preferred solution for mitigating coastal erosion along the Mediterranean coast of Israel, as it is considered “soft” and environmentally friendly. However, using fine sand for nourishment in Israel without supporting measures is problematic due to the high wave energy and strong longshore currents in the littoral zone that tend to drift the sand away. This would require ongoing, multiyear, costly, and never-ending maintenance. In the present study, we analyzed sand and pebble alternatives for nourishment of the eroded beach in front of Tel Ashkelon, an important coastal archaeological site in southern Israel that suffers from severe erosion. Based on Pranzini et al. (2018), we analyzed the alternatives, evaluated their cost and efficiency, and assessed their potential environmental impacts. The study concluded that for protecting the southern part of Tel Ashkelon beach, pebble nourishment is the optimal solution, mainly regarding durability and cost. Using this material for nourishment will better absorb the storm wave impact and protect the foot of the archaeological Tel from erosion, and require lower maintenance cost than using finer sand nourishment.
Beach nourishment
Coastal erosion
Pebble
Longshore drift
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Master project report. Picarras is one of the touristic beaches of Santa Catarina state in Brazil. Picarras beach is a headland bay beach. In the bay irregular features like an island, rocky outcrops and shoals are present influencing wave propagation. In the south Picarras is bounded by Picarras river. The river mouth has been fixated in 1970, after which erosion started. The part just a few hundred meters north of the river jetty has the most severe erosion. The erosion gradually decreases towards the north, where even some accretion has been measured. When the situation became critical a nourishment was executed in 1999, which has disappeared totally on some places. The decrease in beach width causes a devaluation of the houses and a decrease in tourism which consequently leads to a decrease of employment. It is therefore necessary to investigate the causes and the amount of the erosion and to generate measures to counteract the negative impact of the erosion. Prosul, a Brazilian engineering company, has designed a nourishment of which execution started in July 2008. The main goal of this study is investigate erosion at Picarras beach and to design a nourishment to counteract the effects of the current erosion. A model has been built to represent the situation at Picarras beach. With the model the evolution of the nourishment and the evolution of the existing plan of Prosul could be evaluated. The bathymetry has been composed of recent profile measurements and old nautical maps. They have all been related to the reference level of IBGE. To investigate the erosion at Picarras beach the wave climate has been schematised. The available wave data was given for four direction (NE, E, SE, S) in the form of wave heights and periods. To be able to compare what the results of the incoming wave energy from these four directions were on the erosion and accretion on the beach, a schematisation has been made. A representative average wave per direction has been determined, that supplied the same energy input from that direction as did all the different waves from that direction. Headland bay beaches are historically formed in such a way that the incoming waves and thereby the wave energy, arrive perpendicular at the beach, thus absorbing the incoming wave energy in the most efficient way. This theory formed the basis of this schematisation. The mean tidal variation is 0.6m, at spring tide this is 0.9m. Storm surges lead to a set-up in water level of approximately 1.0m. Currents and wind are not taken into account. The sediment present at the beach has a D50 of 0.285mm. The sand used in the nourishment of 1999 was coarser than the native sand, which had a D50 of 0.260mm. Erosion processes can take the sand either in cross-shore direction or in longshore direction. Without looking at the underlying process, just to get a realistic idea of the erosion and accretion patterns, the amount of eroded sediment has been calculated with shoreline changes and deduced erosion rates [2]. The erosion of the past nine years is calculated to be 395,000 m3. To find out where the sediment is transported to at Picarras beach a model has been build. First the nearshore wave conditions have been modelled with Delft3D (D3D) for the four wave scenarios. These conditions serve as input for Unibest (UB). This program is applied to model the shoreline changes.
Headland
Beach nourishment
Coastal erosion
Jetty
Coastal engineering
Breakwater
Plage
Seawall
Shoal
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Contemporary and near-future shoreline change is widely regarded as an issue on small tropical islands. While it is widely anticipated that sea-level rise will precipitate shoreline recession on tropical islands, studies to date record both accretion and recession at historical timescales. This study of Seven Mile Beach, Grand Cayman presents a case study of historical shoreline change in which the local geomorphic setting is shown to be an important influence on shoreline behaviour. Consistent with its leeside setting, historic shoreline analysis (1958–2019) reveals erosion on the margins and accretion in the central part of the headland-embayment beach where no beachrock is present. The beach comprises five discrete, but interlinked subcells delineated by low headlands of exposed beachrock. These headlands have emerged through shoreline recession post-1971 but once exposed have become loci of persistent erosion, suggesting a positive feedback between beachrock and waves. A Category 5 Hurricane generated waves directly opposed to long-term modes and throughout the beach, long-term patterns of shoreline change were temporarily reversed, however, the historic pattern of shoreline change was restored within 2 years. The contemporary patterns of erosion and cell development suggest a reduction in sediment supply leading to cannibalization of relict beachridges on the margins of the embayment and emergence of formerly buried beachrock. The effects of coastal structures and erosion abatement measures were assessed and recommendations for coastal management, including development setback lines are presented.
Coastal erosion
Headland
Longshore drift
Beach ridge
Plage
Beach nourishment
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Lee, H.; Kim, J.; Chang, S., and Kim, I., 2021. Analysis of beach changes after construction of submerged breakwaters. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 300–304. Coconut Creek (Florida), ISSN 0749-0208. This study presents seasonal investigations of submerged breakwaters constructed from 2013 to 2014 as part of a government erosion prevention project in the region of Samcheok-si, South Korea. Parameters, including wave-induced currents, wave heights, beach profiles, and shoreline changes, were investigated to monitor and analyze sand transport trends in the study area. The construction of Gungchon Harbor in 2006 led to the transport of sand from southern Wonpyeong Beach to northern Gungchon Beach, which resulted in an average shoreline retreat of greater than 50 m. However, despite the subsequent construction of the submerged breakwaters, beach erosion continued to occur in adjacent areas. Specifically, a tombolo was generated behind the submerged breakwaters, which led to beach erosion. Rip currents were also typically generated near submerged breakwaters, which play a role in the offshore transportation of sand. Wonpyeong Beach experienced erosion following the construction of Gungchon Harbor, whereas Gungchon Beach exhibited accretion. Moreover, evidence of further erosion was observed near the breakwater construction area. Therefore, this study indicates that detailed monitoring during and after the construction of breakwaters is required to predict potential secondary erosion and understand the erosion mechanism for an optimal breakwater design.
Breakwater
Coastal erosion
Beach nourishment
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The beach nourishment tentative projects of Beidaihe were analyzed,the beach nourishment function of submerged breakwater was simulated with physical model test in order to study the affect of submerged breakwater on wave reduction,the transmission coefficient of the submerged breakwater and the beach nourishment efficacy were discussed.The monitoring data of beach nourishment project approved using offshore submerged breakwater to keep beach is reasonable.And,the eco-friendly offshore submerged breakwater on the application is recommended.
Breakwater
Beach nourishment
Plage
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In Lake Kasumigaura, lakeshore vegetations and sandy beach have been devastated in recent years. To recover the sandy beach in Okisu Area in this lake, beach nourishment has been planned with coastal facilities to stabilize the beach, such as groins, detached breakwaters, artificial reefs and artificial headlands. To evaluate the effect of these facilities, BGmodel proposed by Serizawa et al.(2006) was applied for predicting the three dimensional topographic changes after the nourishment. It is concluded that the most appropriate method is to stabilize the beach using a headland.
Beach nourishment
Headland
Breakwater
Coastal erosion
Plage
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PROENÇA, B., OLIVEIRA, F.S.B.F and SANCHO, F., 2011. Coastal Erosion Management in Algarve (Portugal) — a Beach Nourishment Case Study. In: Micallef, A. (ed.), MCRR3-2010 Conference Proceedings, Journal of Coastal Research, Special Issue, No. 61, pp. 328–334. Grosseto, Tuscany, Italy, ISSN 0749-0208.In the Portuguese southern coast, national and international appeal turns it into a highly relevant area concerning the country's economy. Vale do Lobo is a resort located in the centre of this coast, where the beach has been suffering from erosion problems for several years now. Local interventions have been executed in order to prevent the erosion of the beach, yet the efficiency of such strategy has not been verified.This study's main purpose is to enable a better understanding of the evolutionary trends of the coastline between the Quarteira and Ancño inlet and to analyse the efficiency of the beach nourishment interventions as a protection technique for a coastal environment with the wave energy exposure and geomorphologic characteristics of the present one. The study focussed on a 10-year period, during which, 700×10 and 370×103 m3 of sand with D50=0.76 mm (slightly larger than the D50 of the native beach) were extracted from offshore, and deposited in the foreshore. The wave climate in the study area was processed, analysed and used as input for modelling the nearshore processes. In addition, beach profiles measured alongshore have been analysed to obtain the representative beach profile. Coastlines of different dates have been derived from aerial photographs. The longshore transport model Litdrift and the coastline model Litline were applied to study the sediment dynamics. Litdrift was used to estimate the longshore transport capacity of the beach for the hydrodynamic series considering the representative beach profile previously obtained. These results were then used to calculate the evolution of the coastline due to the incident wave climate with Litline model. Aerial photographs were used to verify the model. The analysis of the two beach nourishments performed allowed inference on the efficiency of this coastal protection technique to delay the erosion process.
Beach nourishment
Coastal erosion
Plage
Coastal Management
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This study documents that since 1923, approximately 350 million cubic yards of sand have been deposited on the US East Coast barrier island shoreline (from Long Island, New York to Fisher Island, Florida), by more than 573 beach nourishment episodes, at 154 locations. On East Coast barrier beaches, the use of beach nourishment to control coastal erosion has increased rapidly since the 1960's. Most of this volume (65%) has been placed by federally sponsored beach nourishment projects, either storm and erosion control projects or navigation projects with beach disposal of dredge spoil. However, the proportion of nourishment projects not involving federal funds (state/local and local/private nourishment projects) has been increasing.
Beach nourishment
Coastal erosion
Plage
East coast
Dredging
Erosion Control
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Beach erosion, a problem along most sandy shores, can be caused by man-induced interventions to the coast or natural processes. Remediation of beach erosion (i.e., beach restoration) along eroding developed beachfronts is commonly practiced in the United States by periodic beach renourishment with or without coastal structures. Rates of erosion within beach fills generally vary greatly, and areas that erode faster than the nourishment average are commonly termed erosional hot spots (EHSs). Delray Beach, located on the southeast coast of Florida, was renourished for the fourth time on December of 1992 with about 914,000 m3 of sand dredged from offshore and placed along 2.7 km of beach. About 448,000 m3 of the fill had eroded away by 2001, about eight and a half years after initial construction. Two beach segments with erosion rates higher than the nourishment average were identified based on analysis of annual beach profile data. About 40% of the eroded volume accrued from one of these beach segments, a 600-m long EHS located on the downdrift end of the nourishment. We evaluated hypotheses to explain EHS development; these included the influence of nearshore features (reefs and borrows) on nearshore wave propagation, variability of grain size alongshore, and changes in shoreline orientation induced by the placement of fill. The nearshore reefs have little to negligible influence on the nearshore waves and are not the cause of the EHSs. Borrow areas significantly influence nearshore waves along the beach. Grain-size differences alongshore were also not the cause of increased erosion of EHS segments since grain sizes are not persistently finer where higher erosion is observed or vice versa. Change in shoreline orientation in the south end of the fill (EHS segment) causes an acceleration of the alongshore currents and an increase in sediment transport potential. Shoreline orientation effects appear to play a relatively more significant role in the development of the EHS in the south end of the fill than the other processes evaluated.
Beach nourishment
Coastal erosion
Plage
Beach ridge
Dredging
Longshore drift
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Yoshida, J., Udo, K., Takeda, Y., Mano, A., 2014. Framework for proper beach nourishment as adaptation to beach erosion due to sea level rise. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 467–472, ISSN 0749-0208.Beach erosion caused by sea level rise is a serious problem for people over the world. Beaches play important roles in disaster prevention, recreational use, and nurturing unique ecosystems. Beach nourishment is capable of maintaining the position of the shoreline and the natural environment. However, applying artificial nourishment to the whole beach area is not a practical method due to high costs and the large quantity sand required. There has been no framework for effective adaptation of beach nourishment to solving coastal erosion issues. In this study, we focus on the beach nourishment as an adaptation to beach erosion due to sea level rise and attempt to construct a framework for proper beach nourishment. The framework for the adaptation proposal is as follows: (i) Prediction of shoreline changes and future beach width due to sea level rise; (ii) Determination of beach width to be protected in terms of disaster prevention, ecosystem conservation and recreation respectively; (iii) Specifying vulnerable areas where the area of and width of the beach Step; (iv) Estimation of sand volume and its cost applied only to the vulnerable area. This framework was applied to Japanese beaches where the determine beach width indicated that when a beach width of more than 10 m is needed for prevention against disasters, more than 20 m for ecosystem conservation, and more than 30 m for recreation use. The volume of sand required to maintain the beach width along the whole Japanese beach varies from 61× 106 to 2,300× 106 m3, and by the use of this framework, it is possible to estimate practical nourishment volume and its associated costs for disaster prevention, ecosystem conservation and recreation use.
Beach nourishment
Coastal erosion
Beach ridge
Coastal Management
Plage
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Citations (12)