Coastal Development, Conservation and Sustainability

Hangzhou Bay is a world-famous strong tidal estuary with an irregular coastline, unique topography, numerous human activities, and complex hydro-sedimentological environment. The Daishan-Yangshan Sea-Crossing Transport Corridor (DSTC) project is located at the mouth of Hangzhou Bay, which is composed of multiple sea-crossing bridges, an underground tube tunnel, and several man-made islands. The large-scale engineering of DSTC fully connects the cities of Shanghai, Yangshan, Daishan, Zhoushan, and Ningbo. This article discusses the morphodynamic responses due to the construction of the DSTC based on a state-of-art numerical model system from the perspective of its impacts on the hydro-sedimentological environment of Hangzhou Bay, as well as on adjacent projects. This study proved that the variation range of tide level in Hangzhou Bay is mostly within 2 cm after the implementation of the DSTC, while that of the man-made island and piers is only within 6 cm. The tidal prism decrease percentage of Hangzhou Bay is less than 0.5%. It does not significantly change the current field and underwater topography in Hangzhou Bay, except near the man-made islands and the bridge. The effect of the DSTC on surrounding ports and channels is small and limited. That is, the proposed DSTC engineering is feasible from the perspective of morphodynamic responses. The conclusions provide a useful reference for similar large-scale estuary construction projects. Full article

Low-crested and submerged breakwaters are frequently employed as coastal defence structures. Their efficiency is governed by wave energy dissipation, and the wave transmission coefficient can evaluate this parameter. The current study conducts experimental investigations on both low-crested and submerged breakwaters exposed to different wave conditions to compare their performance with that of emerged breakwaters. The current study provides a comprehensive review of existing formulae and highlights the impact of design variables. To evaluate the reliability of each existing formula, four “reference” configurations are used. Having these structures at the same overall volume, the results also provide a useful tool for engineers involved in the lowering operation of existing breakwaters. Nature and magnitude of governing parameters are investigated, and some points of criticism are outlined. The comparison results show that few of the existing equations give reliable estimates of the transmission coefficient for all the models tested in this study. Higher values of root mean square error are related to the emerged breakwater rather than the submerged ones. To obtain information about the transmitted wave energy, spectral analysis is applied as well. Different behaviours of the transmitted spectrum, n terms of shape and peak frequency, are highlighted. The results improve the overall knowledge on formulae that are in the literature, in order to make the user more aware. Full article

Novel strategies in coastal protection are needed to cope with climate change-induced sea level rise. They aim at the sustainable development of coastal areas in light of intensification and land use changes. A promising approach is the design of nature-based solutions (NbS), complementing the safety levels of technical infrastructure. However, NbS lack a widespread and large-scale implementation. To address this deficit, co-design concepts are needed that combine experiences from science and practice. This work presents and discusses the approach of a coast-specific real-world laboratory (RwL) addressing the inclusive design of ecosystem-based coastal protection. Strategies of RwLs are applied for the first time in a coastal context along the North Sea coastline in Germany. We found the concept of RwLs suitable for coastal transdisciplinary research, although adaptions in the spatial reference level or flexibility in location and time of experimentation are necessary. A profound actor analysis is indispensable to specify participatory processes and interaction levels. A criteria-based cooperative selection of RwL sites helps to reveal and solve conflicting interests to achieve trust between science and practice. Addressing site-specific characteristics and practitioners’ needs, our coastal RwL provides a mutual learning space to develop and test NbS to complement technical coastal protection. Full article

Climate change and relative sea-level rise (RSLR) will increasingly expose coastal cities to coastal flooding, erosion, pluvial and fluvial flooding, episodic storm-tide flooding and eventually, permanent inundation. Tools are needed to support adaptive management approaches that allow society to adapt incrementally by making decisions now without creating path dependency and compromising decision-making options in the future. We developed an agent-based model that integrates climate-related physical hazard drivers and socio-economic drivers. We used it to explore how adaptive actions might be sequentially triggered within a low-elevation coastal city in New Zealand, in response to various climate change and socio-economic scenarios. We found that different adaptive actions are triggered at about the same RSLR level regardless of shared socio-economic pathway/representative concentration pathway scenario. The timing of actions within each pathway is dictated mainly by the rate of RSLR and the timing and severity of storm events. For the representative study site, the model suggests that the limits for soft and hard protection will occur around 30 cm RSLR, fully-pumped water systems are viable to around 35 cm RSLR and infrastructure upgrades and policy mechanisms are feasible until between 40 cm and 75 cm RSLR. After 75 cm RSLR, active retreat is the only remaining adaptation pathway. Full article

Artificial beaches have made a significant contribution to the expansion of coastal tourism. Obtaining information on tourists’ preferences for artificial beach tourism can help managers to better balance the relationship between the satisfaction of recreational needs and environmental protection. The Meishan Bay Beach Park in Ningbo, Zhejiang Province, China was used as the study site, and the tourists’ preferences for the artificial beach park development and management were evaluated using the choice experiment method. The results revealed that tourists were generally more interested in improving the governance level of the existing landscape than in further expanding the scale of artificial beach development. Among all attributes, significantly reducing the amount of garbage was the most preferred attribute, with a willingness to pay of 39.75 CNY, while willingness to increase beach area was the lowest attribute. The result of the preference heterogeneity analysis showed that tourists with higher education levels were more willing to pay to obtain a better recreational experience, while local tourists were more concerned about reducing congestion. Moreover, we found a clear and relevant segmentation of tourists’ choice behavior, with the strong sensitivity for raising the ticket price being driven by the smallest group of the sample. Full article

Soda residue soil (SRS) is a man-made engineering foundation soil formed by soda residue; it is mainly distributed in coastal areas in China. SRS is rich in a variety of corrosive salts, among which the concentrations of chloride ions are about 2–3 times that of seawater. These highly concentrated chloride ions migrate and diffuse in reinforced concrete (RC) structures built on coastal SRS through multiple transport mechanisms. However, current research on the durability of RC structures exposed to the coastal SRS environment has not led to the publication of any reports in the literature. SRS may be classified by analyzing the quantitative relationships among the corrosive ions it contains. In this paper, the deterioration of RC structures due to the corrosive saline-soil environment in China is discussed, and advances in RC structure durability under such circumstances are reviewed. Our findings show that a corrosive environment, especially when this is a result of coastal SRS, has a significant influence on the deterioration of RC structures, greatly threatening such buildings. A series of effective measures for enhancing the durability of RC structures in saline soil, including improvements in concrete strength, reductions in the water–binder ratio, the addition of mineral admixtures and fiber-reinforcing agents, etc., could provide a vital foundation for enhancing the durability of RC structures which are at risk due to coastal SRS. Vital issues that must be investigated regarding the durability of RC structures are proposed, including the transport mechanism and a prediction model of corrosive ions, dominated by chloride ions (Cl⁻), in SRS and RC structures, the deterioration mechanism of RC materials, a long-term performance deduction process of RC components, durability design theory, and effective performance enhancement measures. The findings of this paper provide some clear exploration directions for the development of basic theories regarding RC structure durability in coastal SRS environments and go some way to making up for the research gap regarding RC structure durability under corrosive soil environments. Full article

Inundation shifts plant growth, species diversity and ecosystem stability, but it remains unclear how inundation depth shapes the phenotypic variability of clonal plants in an estuary wetland. To reveal the response of clonal plant populations to inundation depth, we calculated the variation of Phragmites australis using shoot height, leaf length, leaf width, leaf biomass and panicle length in the Liaohe estuary wetland. Reproductive allocation was defined by the ratio of panicle length to shoot height. Linear regression showed that shoot height, leaf length, leaf width, leaf biomass and panicle length were negatively correlated with inundation depth, while the ratio of panicle length to shoot height was negatively correlated with inundation depth (p < 0.0001). Based on data regarding the statistical differences of plant phenotypic traits among P. australis, we recognized populations had generated variation differentiation. Compared with other functional traits, the coefficient of variation of leaf-related traits were at a high level. Therefore, leaf parameters would be the most suitable, and they increased the area and weight to support the action of plants during floods. Multivariate statistical analysis suggested that P. australis populations in the Liaohe estuary wetland were divided into two phenotypic clusters, consistent with geographical distance and morphological similarity. Our results provide a novel perspective on the ecological strategy of cloned plants under inundation change and offer theories for the conservation and restoration of estuarine wetland ecosystems. Full article

Marine sediments may easily accumulate contaminants, posing a high risk to human health and biota. Beneficial use applications exist for natural sediments and sediments contaminated with organic and inorganic pollutants. In this research, the term marine sediments (MSs) was used to refer to all marine sediments, which could be clean, natural marine sediments, as well as contaminated marine sediments and dredged materials, as the main focus of this research. Sediment remediation often involves costly and time-consuming processes. Assessment frameworks are essential for selecting suitable remediation alternatives for MSs. This research aims to provide regulatory frameworks for the sustainable beneficial use of all marine sediments. No studies have been reported on this issue in Colombia until now. The current states of marine sediments on the Colombian Caribbean Coast were mainly investigated. Concentrations of specific harmful heavy metals (HHMs) in Colombia’s sediments were higher than the environmental standards of various nations. Ex situ remediation technologies were evaluated through cost–benefit analysis and environmental feasibility to be adopted in Colombia. The results identified solidification/stabilization (S/S) as promising technologies. Sustainable remediation of MSs may offer ample opportunities for environmental enhancement and economic benefits. Continuous research and adopting appropriate environmental regulations, such as the London Protocol 1996, would contribute to effectively managing all marine sediments in Colombia. More innovative and cost-effective remediation technologies with beneficial uses would still be needed. Decision makers may use the proposed frameworks to select optimal remediation alternatives and implement sustainable MSs management by achieving their beneficial uses. Full article

Most of the cities of Bengkulu are coastal areas (71.87%) under substantial pressure due to infrastructure development. This condition has affected the mangrove ecosystem and ecological degradation and has induced abrasion. In this study, we aimed to analyze the existing conditions of the mangrove ecosystems in the city of Bengkulu, particularly the composition and distribution of the mangrove species and the determination of the water quality. We collected vegetation data using exploratory methods and direct observation at 13 research sites. We measured the water quality in situ in terms of the temperature, salinity, pH, and dissolved oxygen (DO) at the sites, performed a vegetation analysis, and analyzed the turbidity, total dissolved solids (TDSs), biochemical oxygen demand (BOD), chemical oxygen demand (COD), nitrate, nitrite content, ammonia, and phosphate concentrations ex situ in the laboratory. We found 52 vegetation species in the research sites, which included 11 true mangrove species, 9 associated mangrove species, and 31 coastal and land flora. A total of 24 species are categorized under the least-concern (LC) category of the IUCN (International Union for Conservation of Nature) Red List, and one species is in the data-deficient (DD) category. We categorized the water quality of the mangrove ecosystems in the city of Bengkulu as relatively good, with all the parameters below the national water quality threshold, except for the nitrite concentration in the Bengkulu River estuary. Proper management needs to be developed for the conservation and restoration of mangrove ecosystems to sustain their functions. Full article

During the last decade, growing demand has prevailed for environmental protection and the application of sustainability principles toward the coastal environment. As the coastal zone constitutes one of the first recipients of the impacts of climate change due to the rise in sea level, integrated coastal zone management arises as a significant tool for the study of vulnerable coastal ecosystems. In combination with ICZM, the use of indicators and ecosystem services analysis couples all of the information, leading to an integrated approach and opportunities for a sustainable blue economy in coastal ecosystems. The aim of the present study is to form a protocol for a sustainable blue economy in the coastal zone, which will investigate and define the current capacity and the boundaries of a coastal ecosystem with specific characteristics of industrial activity, cultural heritage, and a protected natural environment. The case study for this research is the Gulf of Elefsis, a special sea basin in the eastern Mediterranean, located a short distance from the Athens metropolitan area. The Gulf of Elefsis is characterized by a developed coastal zone, which includes intense industrial activity, the ancient historical sights of Elefsis, the environmentally protected wetland of lake Koumoundourou, the town of Elefsis, a trade port, and growing shipbuilding activity. Full article