Coastal Protection Strategies Research Articles

Erosion protection by winter state of salt marsh vegetation

The inclusion of coastal ecosystems in coastal protection strategies is highly desired, but for temperate regions it is hampered by uncertainty about the provision of relevant ecosystem services over the annual growth cycle. This flume study compared winter stages of the two salt marsh species Spartina anglica and Elymus athericus with and without above ground biomass to bare soil to assess their protection service against vertical bed erosion in the surf and swash zone. Results yielded no effect of the above ground biomass on mean erosion, even though the species responded differently with E. athericus buckling and S. anglica withstanding the hydrodynamic forcing. Equally, no significant differences were observed between species which is attributed to the comparable dry root biomass and soil bulk density of the used vegetated patches. While this similarity does not allow for establishment of quantitative relationships, the results suggest a species independent erosion protection efficiency persisting throughout the year. This has the potential to simplify the consideration of erosion protection by salt marsh in coastal protection strategies, as it alleviates the need for detailed differentiation on species or seasonal level of this ecosystem service.

Fine Spatial Scale, Frequent Morphological Monitoring of Urbanised Beaches to Improve Coastal Management

Between 1959 and 2010, a coastline retreat of 2.4 m/year and erosion of up to 174 m were recorded around Turbo, in northern Colombia. This degraded coastal system is the result of a poorly planned coastal defence scheme, combined with a lack of formal technical methodologies for diagnosis and monitoring. The coastal system cannot provide the protection services required by the local community. From 2017 to 2019, the group monitored urban beach profiles in a small area close to the town of Turbo, in the wet and the dry seasons, as part of a coastline analysis to identify morphodynamic trends in the area. The results show a net shoreline accretion of up to 30 m and positive sedimentary accumulation of up to 45.8 m3/m. To the north of the study area, sediment accumulation is evident at the Turbo River Delta. The 34 coastal protection structures in the study area have a high k index (~0.7), suggesting that they are the main drivers controlling the trend of sediment accumulation. The correlation of geomorphological, oceanographic, and anthropic variables related to the presence of coastal structures, is necessary in order to set up efficient coastal protection schemes.

Can we enhance ecosystem-based coastal defense by connecting oysters to marsh edges? Analyzing the limits of oyster reef establishment

Nature-based coastal defense schemes commonly value bivalve reefs for i) reducing coastal erosion in the intertidal and for ii) forming fringing reefs near salt marsh edges to protect them against lateral retreat. The capacity for a reef to reduce erosion increases at a higher position in the tidal frame as the lower over-lying water level magnifies the influence of the reef on wave attenuation. Unfortunately, ecological constraints on reef development typically limit their practical application in coastal protection schemes to the lower intertidal, as bivalves grow best with long inundation times. In micro-tidal areas this is a lesser problem, given the close proximity of lower and upper intertidal ecosystems in space. By contrast, in meso- and macro-tidal estuaries, bivalve reefs tend to form hundreds of meters away from existing marshes, nullifying any wave-protective benefits. In this study, we produce evidence that with the assistance of management measures, widespread reef formation is possible on open mudflats, including bordering the marsh edge in meso- and macro-tidal estuaries, where natural reef formation is normally strongly limited.In four locations throughout the meso- to macro-tidal Dutch Scheldt estuary, we observed the presence of individuals of two major intertidal reef-forming bivalves, Pacific oysters (Crassostrea gigas) and blue mussels (Mytilus edulis), within low-lying Spartina anglica-dominated marshes. As these communities lie well outside of the expected range of reef formation, this observation suggests the existence of mechanisms that extend the habitable range of these bivalves. In a series of field experiments, we first demonstrate how the stabilization of shell-substrate within the marsh promotes successful establishment and adult survival. Secondly, by placing artificial stable substrate in transects from the subtidal up to the marsh edge, we demonstrate that bivalve establishment is possible throughout a much larger range of the intertidal than where natural reefs occur. The effectiveness of stable substrate in stimulating bivalve establishment is likely a consequence of bridging size-dependent thresholds that limit the effective range for natural reef formation on tidal flats. The success of this approach is tempered by a consistent decrease in reef size and growth at higher elevations, suggesting that the optimal reef position for utility in coastal defense lies at an intermediate tidal position, well above the observed range of natural occurrence, but below the maximum achievable upper limit of reef formation. Together this work provides a pathway forward concerning how artificial reefs may be fostered to increase their utility as a nature-based flood defense measure.

A methodological framework for determining an optimal coastal protection strategy against storm surges and sea level rise

Interdependent critical infrastructures in coastal regions, including transportation, electrical grid, and emergency services, are continually threatened by storm-induced flooding. This has been demonstrated a number of times, most recently by hurricanes such as Harvey and Maria, as well as Sandy and Katrina. The need to protect these infrastructures with robust protection mechanisms is critical for our continued existence along the world’s coastlines. Planning these protections is non-trivial given the rare-event nature of strong storms and climate change manifested through sea level rise. This article proposes a framework for a methodology that combines multiple computational models, stakeholder interviews, and optimization to find an optimal protective strategy over time for critical coastal infrastructure while being constrained by budgetary considerations.

Regional economic analysis of flood defence heights at the German Baltic Sea coast: A multi-method cost-benefit approach for flood prevention

Mean and extreme sea-level uncertainties, as well as uncertainty about future flood exposure, hinder the risk-based optimisation of flood protection investments. To deal with these uncertainties, cost-benefit analysis (CBA) and methods for robust decision-making can be combined. This paper sequentially applies CBA, robust optimisation methods and info-gap analysis to find efficient and robust coastal flood protection strategies for the German Baltic Sea coast. The CBA results suggest that – under flood risk assumptions – a share of the coast of Schleswig-Holstein (9.3–10.1%; 60–65 km) and Mecklenburg-Vorpommern (4.1–10.0%; 78–189 km) with relatively high flood exposure, might currently be under-protected from a social welfare perspective. Present Value estimates of regional investment costs of five regret or loss minimising strategies range from 1.7 to 4.8 billion Euro across robustness metrics at 3% discounting. The info-gap analysis suggests that some of these strategies will fail to prevent large-scale damages under high-end scenarios. We conclude that a multi-method cost-benefit approach can be used to narrow down the number of solutions that are both potentially efficient and sufficiently robust by investigating strategy performance within, across and beyond predefined scenarios.

滨海湿地消浪服务空间分布特征——以上海市崇明岛为例

全球气候变化增加了滨海地区遭受侵蚀、风暴潮等灾害的风险，利用自然湿地的消浪功能增强海岸防护是当前研究的热点，但目前对消浪服务的空间分布评估研究相对匮乏。以上海市崇明岛环岛滨海湿地为例，结合GIS与Kobayashi指数形式波高衰减模型评估常规状态下湿地消浪服务的空间分布特征。结果显示，大、小潮升条件下，崇明环岛湿地消波的平均高度分别为0.94、0.54 m与效度分别为83.6%、60.4%，消波高度的空间分布表现为南岸小于北岸，消波效度的空间分布在小潮升时与消波高度相似，而大潮升时南岸的消波效度有明显提升。物理环境与生物因素空间分布及其相互作用的异质性，导致消浪服务的空间分布也具有空间异质性。实际参与消波的断面宽度与不同景观消波服务的评估结果表明，一个断面的所有景观并非都参与到消浪过程中，即使在大潮升时期，不同岸段景观的平均参与度不足71%。潮高与波高的增加并不会使参与消波的景观规模成对应比例的增加，说明消波服务在空间上具有明显的非线性特征。研究可为滨海湿地生态修复空间规划、基于生态系统的海岸带管理、自然资本核算提供科技支撑。;Global coastal zone is faced with the challenge of increasing threats from sea level rise, coastal erosion and storm surge as the result of climate change. To improve the adaptability of the coastal area to climate change, many scientists proposed to incorporate wetlands wave attenuation service into conventional coastal protection schemes, despite the knowledge gap of the spatial distribution of such service. In this study, we incorporated an exponential wave propagation model into GIS, and simulated the spatial distribution of the wave attenuation service of the coastal wetlands in Chongming island, Yangtze Estuary, under two normal scenarios (spring rise and neap rise). The results showed that coastal wetlands could reduce average significant wave heights up to 0.94 m and 0.54 m, accounting for 83.6% and 60.4% of their incoming wave heights under spring rise and neap rise, respectively. In either case, wave height reduced by the wetlands on the southern coast of Chongming island was lower than that on the northern coast. The spatial characteristics of wave attenuation rate was similar to that of the reduced wave height under neap rise. Compared to the neap rise scenario, wave attenuation rate of the wetlands along the southern coast of Chongming island showed a significant improvement under spring rise. The spatial heterogeneity of the wave attenuation service can be explained by the spatial patterns of coastal physical and biotic factors as well as their interactions. Not the whole transects of vegetation contributed to wave attenuation, even under spring rise scenario. Only a part of the transects, 70.8% in average, were engaged in wave attenuation under spring rise. This result indicates that the increased height of tide and wave may not induce the corresponding proportion increase in the width of ecosystem involved in dissipating waves due to the non-linear feature of ecosystems' wave attenuation service in space. This study can provide important support for coastal wetland restoration, ecosystem-based coastal management, and natural capital accounting.

GUIDELINES FOR DESIGNING SAND NOURISHMENT ON LOW TO VERY EXPOSED COASTS

Danish law establishes a common right of passage on foot along the Danish shoreline, even though beaches are often privately owned. The law also states that coastal protection must not hinder this. Therefore, sand nourishment should be part of every coastal protection scheme against erosion. Sand nourishments can be designed in numerous ways depending on their objectives. As part of the European Interreg project, Building With Nature (BWN), guidelines will be developed by the Danish Coastal Authority (DCA) in end-2020. This abstract presents these guidelines with special focus on the coasts of Denmark. Special emphasis will be on insight into the natural variation of the coasts, as this is vital both when designing effective coastal protection schemes and when evaluating the impact of the nourishment. In this project, the pathway along which sediment is being transported spans from offshore at the outer bar to the coastal cliff. The aim is to be able to determine the along- and cross-shore paths, along which the nourishment sand is transported, the diffusion velocity of the nourishment and the impact on the surrounding coasts. Based on the results of the multiple analysis, the primary objective is to produce guidelines on how to use sand nourishment to counteract erosion in a sustainable and socioeconomic way.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/nIrFFmH98V8

Multimodal transportation system protection against sea level rise

Transportation infrastructure resilience is an important component of a region’s ability to recover from natural disasters. While Sea Level Rise (SLR) is becoming inevitable with climate change, little is known of the impact of protection strategies on multiple modes of transport. The present paper proposes a framework where a range of coastal protection strategies are undertaken in the case of one meter of SLR (expected by the year 2100). The methodology incorporates high-resolution hydrodynamic simulations using the Coastal Storm Modeling System (CoSMoS) and traffic simulations using the Multi-Agent Transport Simulation (MATSim) to quantify the potential impact of SLR and protection strategies on both the highway and public transit systems in the San Francisco Bay Area.The results of the traffic simulations are analyzed at the regional and Transportation Analysis Zone (TAZ) levels. Modeling results show that coastal protection of one area will affect the transportation system (sometimes negatively) in areas beyond its vicinity. The improved spatial resolution, and the integration of highway and transit networks in a unified model, reveal transportation phenomena that were not identified in previous studies. By quantifying the impacts on commuters’ mobility in different TAZs, the methodology can be used to develop effective and inclusive strategies against SLR for a given region of interest.

Long-term Changes of Waves at the German Baltic Sea Coast: Are There Trends from the Past?

Dreier, N.; Mannikus, R., and Frohle, P., 2020. Long-term changes of waves at the German Baltic Sea Coast: Are there trends from the past? In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020.JournalofCoastalResearch,SpecialIssueNo.95,pp.1416–1421.CoconutCreek(Florida),ISSN0749-0208.For the development of future coastal and flood protection strategies and methods as well as the adaptation of today's existing protection structures, possible impacts of climate change on the long-term changes of the local wave conditions in the future and the past need to be analysed and assessed. In this study, two main research questions are raised: (i) Are there any long-term changes of the waves derived from numerical model data?, (ii) How well can the COSMO model reproduce the wave climate for the past? To answer those questions, two reanalysis wind data sets (COSMO-REA6 and coastDat2) for the past based on the COSMO model are used for the calculation of long-term time series of hourly wave parameters (SWAN) at the German Baltic Sea Coast. The long-term changes of the average wave conditions in the past are analysed and assessed for the coastDat2 data set for both average values and the frequency of occurrence of significant wave height and mean wave direction over time periods of 30 years. Moreover, the statistical significance of the changes of the frequency is assessed based on statistical hypothesis tests. In agreement with previous analysis of the future long-term changes of the wave climate, a large multi-(decadal), spatial and seasonal variability of the changes exist and the changes depend on the exposition of the coast towards the prevailing westerly winds. At westerly wind exposed locations, trends towards an increase of the 30 year annual averages of significant wave height up to 5 % were found, with possible larger changes of the 30 year seasonal averages, and trends towards more waves coming from westerly directions. The long-term changes of extreme wave conditions in the past are analysed based on extreme value statistics and over time periods of 30 years. Slightly increasing respectively decreasing trends between -5 % and +9 % (-0.16 m/+0.27 m) of significant wave heights with a return period of 200 years have been found at westerly respectively easterly wind exposed locations.

Using Historical Responses to Shoreline Change on Australia’s Gold Coast to Estimate Costs of Coastal Adaptation to Sea Level Rise

Climate change impacts, sea level rise, and changes to the frequency and intensity of storms, in particular, are projected to increase the coastal land and assets exposed to coastal erosion. The selection of appropriate adaptation strategies requires an understanding of the costs and how such costs will vary by the magnitude and timing of climate change impacts. By drawing comparisons between past events and climate change projections, it is possible to use experience of the way societies have responded to changes to coastal erosion to inform the costs and selection of adaptation strategies at the coastal settlement scale. The experience of implementing a coastal protection strategy for the Gold Coast’s southern beaches between 1964 and 1999 is compiled into a database of the timing, units, and cost of coastal protection works. Records of the change to shoreline position and characteristics of local beaches are analysed through the Bruun model to determine the implied sea level rise at the time each of the projects was completed. Finally, an economic model updates the project costs for the point in the future based on the projected timing of sea level rise and calculates a net present value (NPV) for implementing a protection strategy, per km, of sandy beach shoreline against each of the four representative concentration pathways (RCP) of the Intergovernmental Panel on Climate Change (IPCC) to 2100. A key finding of our study is the significant step-up in expected costs of implementing coastal protection between RCP 2.6 and RCP 8.5—from $573,792/km to $1.7 million/km, or a factor of nearly 3, using a social discount rate of 3%. This step-up is by a factor of more than 6 at a social discount rate of 1%. This step-up in projected costs should be of particular interest to agencies responsible for funding and building coastal defences.

On the Natural and Anthropogenic Drivers of the Senegalese (West Africa) Low Coast Evolution: Saint Louis Beach 2016 COASTVAR Experiment and 3D Modeling of Short Term Coastal Protection Measures

Ndour, A.; Ba, K.; Almar, A.; Almeida, P.; Sall, M.; Diedhiou; P.M., Floc'h, F.; Daly, C.; Grandjean, P.; Boivin, J-P; Castelle, B.; Marieu, V.; Biausque, M.; Detandt, G.; Tomety Folly, S.; Bonou, F.; Capet, X.; Garlan, T., Marchesiello, P.; Benshila, R.; Diaz, H.; Bergsma, E.; Sadio, M.; Sakho, I., and Sy, B.A., 2020. On the natural and anthropogenic drivers of the Senegalese (West Africa) low coast evolution: Saint Louis Beach 2016 COASTVAR experiment and 3D modeling of short term coastal protection measures. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 583-587. Coconut Creek (Florida), ISSN 0749-0208.West Africa's low and densely populated coasts crystallize most of the environmental and societal problems and resulting vulnerability. It is becoming urgent to document this coast and the natural and anthropogenic forces to understand its evolution. Saint Louis is a historic (World Heritage) city located on the Langue de Barbarie, a 10 km sandspit at the mouth of the Senegal River. Because of its location, it is vulnerable (erosion, flooding) to river and ocean variability. This intermediate barred microtidal beach is located in a storm-free intertropical environment, but is exposed to distant oblique energetic waves from high latitudes, causing one of the highest coastal drifts in the world (∼800,000 m3/year). As part of the COASTVAR project, an intensive international field experiment was conducted in Saint Louis from 4 to 13 December 2016 to quantify the natural protective role played by the sandbar, coastal currents and transient exchanges with the inner shelf. Many instruments have been deployed to measure waves, currents, bathymetry and topography. This article provides an overview on the objectives of the experiment, the deployment and the first results of the modeling of coastal protection strategy.

Beach nourishment practice in mainland Portugal (1950–2017): Overview and retrospective

A compilation of all beach nourishment projects conducted along mainland Portugal was made, totalizing 134 interventions up until 2017. The objectives, type of deposition, borrow area, responsible entities and geographic distribution of each intervention were identified and are herein briefly presented and discussed. Beach nourishments were mostly carried out to improve the stability of the coastline, as a mitigation measure for coastal erosion, and to increase beach width for recreational use, as a tool for adding value to the coast. Operations concentrated in: 1) urban areas where erosion can pose risks to people and assets, 2) close to river mouth/inlets where port structures are established, and 3) touristic areas with high recreational value. Port Administrations contributed most (in number and volume) for the nourishment operations (62% of all operations), favouring the placement of the dredged sediments on the nearshore, and, more recently, providing the sediment of opportunity for subaerial beach fills and/or dune reinforcement carried out in cooperation with the State Environment/Coastal Authorities. The increase in the number of beach nourishments was accompanied by a decrease in the number of "hard" coastal structures, concurring to the optimization of an integrated coastal sediment management policy, in a clear paradigm shift that started in the 90s in regard to the coastal protection/defence strategy. There is a growing awareness regarding the beneficial use of sediments dredged by Ports to counter the coastal sediment deficit, making coastal nourishments mainly supply-driven in mainland Portugal. Beach nourishment practice has evolved to be the major contributor to a regional and national-scale coastal protection strategy focused on coastal sediment management.

An assessment of measured and computed depth of closure around Japan

The development of effective coastal adaptation strategies and protection schemes is a major challenge for coastal zone managers and engineers, not only because the coastal zone is the most populated and developed land zone in the world, but also due to projected climate change impacts. A priori knowledge of the so called depth of closure (DoC) is, more often than not, a pre-requisite to understand and model coastal morphological response to wave forcing, which in turn enables the design of appropriate coastal adaption/protection measures. In the absence of long term measurements of coastal profile data, the DoC is often computed using Hallermeier’s formulations or derivatives thereof, for applications around the world. However, there are two major unresolved issues associated with computing the DoC in this way: the accuracy of the wave data required for reliable DoC computations, and the generic applicability of the coefficients used in DoC equations. This study exploits the availability of DoCs derived from multiple measurements of coastal profiles and wave data along the Japanese coast together with wave reanalysis products to evaluate the validity of DoC calculation approaches. Results show that the accuracy of computed DoC values determined using wave reanalysis data is limited, particularly when the spatial resolution of the wave reanalysis data is lower. Furthermore, coefficients of DoC equations proposed in previous and present studies appear to be location specific and points toward the need for a concerted worldwide meta-analysis that compares observed and derived DoC in order to derive a globally applicable formulation for DoC computations.

Monitoring underwater nourishments using multibeam bathymetric and backscatter time series

Natural and man-induced coastal erosion endanger life and environment in coastal areas worldwide. For sedimentary barrier coasts, beach and underwater nourishments are an efficient coastal protection strategy. To optimize nourishments and to understand their impact on the marine environment, monitoring strategies are required. In this study, we investigate the potential of multibeam echosounder (MBES) data, providing both bathymetry and backscatter (BS), for monitoring the evolution of the nourished sediment and morphodynamics over time. A time series of seven MBES measurements, as well as two sets of box cores, vibrocores and seismic data were acquired of a channel-side nourishment near the Wadden Sea island Ameland (The Netherlands), between April 2017 and May 2019. In general, a high confidence of the acoustic reliability of the BS time series measurements is demonstrated. The unsupervised Bayesian classification method, supported by ground-truthing, is employed to produce a time series of sediment maps, revealing sediments ranging from sandy mud to sand with varying amounts of shell fragments. Based on the sediment maps, the nourished sediment could be distinguished from the natural sediment. Within one year, the shell-rich pre-nourishment seabed is recreated by washing out finer sediments, which are deposited towards the main tidal channel. Using the seismic data and vibrocores, the shell-rich pre-nourishment seabed could be identified in the subsurface after being buried by the nourishments, supporting the general findings. Furthermore, a rapid development of steep bedforms with increasing sediment sorting is observed in parts of the nourished areas. This study shows that high-resolution sediment maps obtained from a time series of MBES BS together with bathymetry reveal morphodynamic and sedimentary processes of nourishment evolution and can advance underwater nourishment strategies.

Promises and perils of sand exploitation in Greenland

Ice flow dynamics of the Greenland ice sheet control the production of sediment. Future acceleration in glacial flow and ice sheet melt will amplify Greenland’s supply of sediment to the coastal zone. Globally, sand and gravel reserves are rapidly depleting while the demand is increasing, largely due to urban expansion, infrastructural improvements and the enhancement of coastal protection in response to climate change. Here, we show that an abundance of sand and gravel provides an opportunity for Greenland to become a global exporter of aggregates and relieve the increasing global demand. The changing Arctic conditions help pave a sustainable way for the country towards economic independence. This way, Greenland could benefit from the challenges brought by climate change. Such exploitation of sand requires careful assessment of the environmental impact and must be implemented in collaboration with the Greenlandic society. Sand and gravel have become important commodities due to infrastructure and coastal protection schemes, leading to shortages on a global level. This Perspective looks at how Greenland could diversify its economy towards export of its sand resources and the potential impacts on the environment and local way of life.

Erosion processes driven by monsoon events after a beach nourishment and breakwater construction at Uswetakeiyawa beach, Sri Lanka

The first beach nourishment project in Sri Lanka was carried out in 2012 over a 1.8-km stretch in the Uswetakeiyawa area by the Coast Conservation Department. About 300,000 m3 of offshore sand in the Indian Ocean was pumped using a dredging vessel for the nourishment. Three breakwaters were constructed nearly 1 year after the beach nourishment. This research was carried out to analyze the performance of the above soft and hard engineering coastal protection strategies. Beach profiles and grain size data were collected over a 1-year period. This monitoring program covered entire seasonal cycles with a comparison to the pre-nourishment beach profiles. Satellite images were also analyzed spanning much larger time periods from 2010 to 2015. Beach profile data indicated both sand accretion and erosion in the nourished area. However, the variations of sand deposition showed enhancement of the sand volume. Satellite images indicated the irregular changes of the beach profiles after the construction of breakwaters. The field observations and calculated relationships of the breakwaters demonstrated either subdued salient or gap erosion at the specific locations of the nourished beach. In this study, no permanent or periodic tombolo formations were observed at Uswetakeiyawa beach. The lack of sediment supply from longshore currents and the high-energy cross-shore monsoon currents can enhance coastal erosion related to the presence of the breakwater.

Longshore wave variability along non-straight coastlines

The present paper demonstrates the role of wave direction and shoreline alignment on wave attenuation along a non-straight coastline. A numerical model was calibrated against measured data at six locations along a non-straight coastline and a hybrid method composed by wave case selection/simulation and nearshore time series reconstruction was applied to transfer 20 years of wave time series from offshore to nearshore. The results highlight the importance of the orientation of the coastline to different degrees of wave exposure to the wave attenuation process. The varying orientation of the coastline, at each of the six sites, resulted in non-uniform wave attenuation alongshore under different wave directions. The extreme wave conditions at each of the sites were also shown to vary significantly along the coast, e.g. ∼18% alongshore (at −17 m Australian Height Datum - AHD) and as much as 34% from offshore (−70 m AHD) to nearshore (−17 m AHD). The results presented here reinforce the importance of assessing variations in wave attenuation along the coast as opposed to simply using the closest offshore wave dataset available. Improved understanding of nearshore wave attenuation along non-straight coastlines aids in better informing future coastal protection and management strategies.

Developing a Sustainable Strategy for Coastal Lands: Case Study Taiwan

All countries are addressing the drastic climate changes as high priority issues. The impact of climate change on coastal land use in Taiwan has been especially severe due to the country's long coastline. As such, developing strategies to promote the protection of coastal land is critical for the sustainable development of the land. At present, even though the central government has developed the relevant adaptation strategies and implementation plans in response to climate change. Due to the limited resources, determining which protection strategy should be implemented as a top priority will require a strategic evaluation for planning and reference purposes.While most of the existing literature on coastal land use has been focused on the establishment of a vulnerability index along with an analysis of adaptation strategies very little of the existing literature discusses research that has been conducted in relation to an in-depth analysis of climate change and coastal land use. Therefore, this study uses the fuzzy analytic hierarchy process to conduct an exploration of coastal land use and protection strategy. The study compiled the literature and related data to establish five major assessment dimensions and 16 protection strategy evaluation indicators. After the empirical investigation and analysis, the findings demonstrated that the designation of coastal conservation areas is the most important aspect in terms of strategies to protect coastal land, followed by land subsidence control and the establishment of land disaster warning systems.

Evaluation of the new coastal protection scheme at Mamaia Bay in the nearshore of the Black Sea

The target area of the proposed study, Mamaia beach, is a narrow stretch of sand barrier island that sits between the Siutghiol Lake and the Black Sea. In the northern part of the bay, is located the Midia Port, where between 1966 and 1971 a long extension of 5 km of the offshore was built. Because of this extension, the natural flow of sediments has been significantly changed. Thus, the southern part of the Mamaia Bay had less sand nourishment which meant that the coast was eroding and to prevent it a protection of six dikes was built. After approximately forty years of coastal erosion, the south of the Mamaia Bay had in 2016 a new protection scheme, which includes first of all the beach nourishment and a new dike structure (groins scheme for protection) to protect it. From this perspective, the objective of the proposed study is to evaluate the effectiveness of the old Master plan against the new one by modeling the outcome of the two scenarios and to perform a comparison with a third one, in which the protection dikes do not exist and only the artificial nourishment has been done. In order to assess the wave processes and the current patterns along the shoreline, a complex computational framework has been applied in the target area. This joins the SWAN spectral phase averaged model with the 1D surf model. Furthermore, new UAV technology was also used to map out, chart and validate the numerical model outputs within the target zone for a better evaluation of the trends expected in the shoreline dynamics.

Is ecosystem-based coastal defense a realistic alternative? Exploring the evidence

Low Elevation Coastal Zones (LECZ) are located at less than 10 m above sea level. Because of human encroachment, combined with sea level rise and increased storminess, LECZ are at an increasing risk of flooding and erosion. In consequence, there is a growing need for shoreline protection. Traditionally, hard infrastructure was used, with positive local results, but negative regional impacts when flows were not maintained. Therefore, ecosystem-based coastal protection has been considered as an alternative. We explored the scientific literature to look for evidence that proves the effectiveness of natural ecosystems for protection against flooding and erosion, when these events are a problem to society. We found that although the protective role of vegetation has been mentioned for over 50 years, most of the studies date from the last decade and have been performed in the USA and the Netherlands. Mangroves, saltmarshes and coastal dunes are the ecosystems most frequently studied. The evidence we found includes anecdotal observations, experimental tests, mathematical analyses, models and projections, economic valuations and field observations. Although mostly effective, there are limitations of an ecosystem-based approach and probably, different strategies can be combined so that protection is improved while additional ecosystem services are maintained. We conclude that, besides improving coastal protection strategies, it is fundamental to reduce human pressure by mobilizing populations inland (or at least promoting new developments further inland), and minimizing the negative impact of human activities. We need to be better prepared to deal with the climate change challenges that will affect LECZ in the not very distant future.