Coastal Land Reclamation Research Articles

Salt marsh restoration: an overview of techniques and success indicators.

Coastal wetlands including salt marshes are among the most productive ecosystems on Earth. They are known for improving the quality of coastal water and provisioning coastal fisheries. However, this ecosystem is under potential threat due to urban coastal land reclamation, limited sediment supply, increased nutrient/eutrophication, and sea level rise. Therefore, restoration efforts to protect the degraded salt marsh habitat are considerably increasing worldwide. In this paper, we present an overview of salt marsh restoration techniques and success indicators. Published scientific literature in English language was collected by searching the most relevant keywords from popular search engines, namely, Google Scholar, Scopus, and Mendeley to get the information about salt marsh restoration techniques and success indicators. This study comprehensively reviewed data from 78 peer-reviewed papers. Results indicated that much of the salt marsh was restored through assisted abiotic strategies (e.g., recovery of tidal exchange, managed realignment, and sediment level amendment). A total of 214 indicators were found, spanning over six major ecological attributes such as structural diversity, ecosystem functions, physical conditions, species composition, external exchange, and absence of threat. Author keywords analysis revealed several hotspots for recent research (e.g., 16s rRNA, fungi, microbial communities, carbon accumulation, and blue carbon). This paper proposes a model for restoring degraded salt marsh, as well as tracking their success.The information presented here will assist the marine ecosystem restoration practitioners in getting a comprehensive understanding of salt marsh restoration success evaluation.

A quantitative approach for offsetting the coastal reclamation impacts on multiple ecosystem services in the Yellow River Delta

Reclamation of coastal wetlands causes the loss of multiple ecosystem services, necessitating that measures to address these impacts be taken. Offset ratios are commonly used to determine the extent of habitat areas that need to be restored elsewhere to achieve no net loss in wetlands; however, most calculation methods focus on individual impacts. In this study, a mathematical model accounting for multiple ecosystem services and their synergies or trade-offs relationships was developed to determine the required allocation of compensation area, and optimal amount of offsetting based on calculated ratios between damaged and compensated habitat areas. We took the Yellow River Delta in China as a case study, calculated the impacts on ecosystem services of different coastal reclamation types, and quantified the offset ratios for restoration based on different compensation scenarios accounting for time lags. We estimated that the offset ratios for the conversion of coastal wetlands into mariculture were smallest among all the reclamation types. We showed that compensating for carbon storage and water regulation with trade-offs will require higher offset ratios than those based on biodiversity only, and will also be more flexible. Our findings suggested that trade-offs and synergetic relationships should be prioritized when making decisions regarding the restoration of multiple ecosystem services. The findings presented herein will facilitate design of biodiversity offsets for coastal land reclamation based on their different impacts on ecosystem services. Overall, the results of this study have important implications for the ecological restoration and compensation of coastal wetlands in the face of coastal land reclamation.

Land reclamation pattern and environmental regulation guidelines for port clusters in the Bohai Sea, China.

Coastal land reclamation (CLR), particularly port reclamation, is a common approach to alleviating land shortages. However, the spatial extent, percentages, and processes of these newly reclaimed ports are largely unknown. The Bohai Sea is the most concentrated area of port reclamation worldwide. Thus, this study addresses the changes in the different coastline types and port reclamation process in the area. The reclamation area of the 13 ports in the Bohai Sea in 2002-2018 was 2,300 km2, which decreased the area of the sea by 3%. The natural coastline length in Tianjin decreased by 47.5 km, whereas the artificial coastline length increased by 46.6 km. Based on the port boundary, however, only 26.3% of the reclaimed areas have been used for port construction, which concentrates in the Tianjin and Tangshan ports. The ratio of built-up area within the ports is only 32.5%, and approximately 48.3% of the reclaimed areas have no construction projects. The port land reclamation in the Bohai Sea has been undergoing periods of acceleration, peak, deceleration, and stagnation since 2002. Hence, future port reclamation should not be totally prohibited, and fine management should be conducted based on the optimization of the reclaimed port area. The innovation of this research is its analysis of the port internal land use pattern, the percentage of built-up area in the ports, and the sustainability of port reclamation policies. The findings have vital implications for scientifically regulating the spatial pattern and exploring the utility of port reclamation.

Nitrogen cycling in plant and soil subsystems is driven by changes in soil salinity following coastal embankment in typical coastal saltmarsh ecosystems of Eastern China

Recently, coastal land reclamation through the use of embankments has increased worldwide, and its impacts on ecosystem processes and functionality have been widely reported. However, the ecosystem nitrogen (N) cycling turnover processes following the establishment of coastal embankments remain unknown. For this study, we investigated stocks of various types of N in soils, N storage in plant subsystems, the microbial immobilization and mineralization of N, as well as soil physiochemical properties in embanked and adjacent unembanked Spartina alterniflora, Suaeda salsa, and Phragmites australis saltmarshes in the coastal wetlands of China. Coastal embankments in a S. alterniflora saltmarsh significantly decreased the total plant N storage by 50.24%, concentrations of total soil organic N (SON) by 55.16%, ammonia nitrogen (NH4-N) by 32.33%, nitrite nitrogen (NO2-N) by 41.23%, nitrate nitrogen (NO3-N) by 13.38%, and the value of soil net ammonification (RA) by 83.49%. However, in P. australis saltmarshes they significantly increased the total plant N storage by 160.24%, concentrations of SON by 57.28%, NH4-N by 7.89%, NO2-N by 101.76%, NO3-N by 32.05%, and the value of RA by 392.95%. Nevertheless, there were no significant differences in N cycling following the establishment of coastal embankments in S. salsa saltmarshes. Significant changes in the organic and inorganic soil N pools of S. alterniflora and P. australis saltmarshes were driven by plant residue inputs, which were significantly affected by decreasing soil salinity in these coastal wetlands. Furthermore, our results indicated that coastal embankments altered the immobilization of soil N and mineralization of microorganisms by influencing the growth and activities of soil microbes, which were primarily associated with changes in soil organic and inorganic N pools following the development of coastal embankments. In summary, alterations in the organic N inputs of plants were initiated by the dramatically decreased soil salinity, which was the main determinant that drove N cycling in the soil subsystems of coastal wetlands subsequent to the establishment of coastal embankments.

Satellite derived coastal reclamation expansion in China since the 21st century

Since 2000, many coastal land reclamation projects have been implemented in China to alleviate the shortage of coastal land resources with rapid urban sprawl and economic growth. As a result, both the length and proportion of artificial shoreline increased significantly. Meanwhile, coastal reclamation inevitably brings some negative environmental and ecological issues, such as biodiversity loss, water pollution, and wetland degradation. In this study, based on the GlobeLand30 product and the OpenStreetMap based coastline data, we tracked the coastal reclamation expansion in China in the 21st century. Specifically, we analyzed the coastal reclamation intensity and coastal reclamation types of all coastal provinces in China, and explored the relationship between reclamation intensity and GDP growth to understand the reclamation status of coastal areas during 2000–2020. Our results showed that the total area of reclaimed land along the coast in China was 5135.31 km2, of which artificial land and aquaculture were two main land-use/land-cover (LULC) types, accounting for 71.89% of the total reclamation area. Among all coastal provinces, Tianjin exhibited the greatest reclamation intensity (i.e., 7.16 km2 km−1) and Zhejiang Province had the largest reclamation area (i.e., 1304.65 km2). We also found the positive correlation between economic development and coastal reclamation. In addition, the progress of coastal reclamation activities has been greatly slowed down owing to national policies released in recent years.

Simulation of the climatic changes around the coastal land reclamation areas using artificial neural networks

For the last 20 years, Istanbul has intensely experienced land use/cover change (LUCC) as a result of both the direction of investment strategies to the construction sector and urban transformation works. Within this process, the demand for the disposal of debris from building demolitions with minimum cost has made the creation of land reclamation areas a current issue. Land reclamation areas that pose a threat to the marine ecosystem also have effects on the local climate, depending on the LUCC experienced on the urban surface. In this study, two coastal reclamation areas of Istanbul (Yenikapı, Maltepe) were addressed, and the predictability of changes in the thermal environment after the landfill was examined using Artificial Neural Networks (ANN). When the relationship between the simulation data and the actual changes was statistically tested, correlations between the original and the simulated images of Maltepe and Yenikapı are 0.650 and 0.710 respectively were obtained. Also, it was determined that the simulations provided exact results in the range of 37–55%, and accurate results in the range of 66–87% with a sensitivity of 100 m. These results revealed that the simulations performed by the ANN have sufficient sensitivity for monitoring the thermal changes in urban areas.

Tracking changes in aquaculture ponds on the China coast using 30 years of Landsat images

Although coastal aquaculture ponds provide high-quality fish protein for billions of people, they are threatened by urbanization, pollution, and climate change. Moreover, colossal aquaculture ponds pose damages such as natural wetland shrinkage and water quality deterioration. However, understanding the trends and drivers of coastal aquaculture ponds on a national scale remains a challenge. In this study, a decision-tree classifier was used to quantify the spatiotemporal distribution of aquaculture ponds over last 30 years in 12 provinces located on the coast of China. Moreover, we analyzed their trends and drivers, including geographical conditions, socioeconomic factors, and development policies. The key results of the study include the following: (1) from 1990 to 2020, the cumulative area and holding area of aquaculture ponds reached 21997.90 km2 and 9613.66 km2, representing 3.7-fold and 1.6-fold increase, respectively, than the 1990 values. Based on geographical conditions, most aquaculture ponds tend to be located in coastal plains and bays following the distribution of low-lying land. (2) Influenced by different levels of socioeconomic development and changed policies, the holding area of aquaculture ponds experienced a “rapidly increasing period” from 1990 to 2011, growing by 246 km2 per year; “stable period” between 2011 and 2017; and “sharply shrinking period” after 2017 declining by 417 km2/year. (3) Coastal land reclamation played a critical role in the expansion of aquaculture ponds by cumulatively contributing approximately 22% of the land resource in the past 30 years. In the future, as a result of increasing land competition, the extent of aquaculture ponds on the China coast tends to decrease continually.

Impacts of Agricultural Land Reclamation on Soil Nutrient Contents, Pools, Stoichiometry, and Their Relationship to Oat Growth on the East China Coast

Agricultural land reclamation of coastal tidal land (CTL) with organic amendments may modulate the soil properties, and therefore promote crop growth. However, the linkages between soil nutrient contents, pools, stoichiometry, and crop growth under the supplement of organic amendments in CTL is limited. In this study, six treatments including the control (CK), organic manure (OM), polyacrylamide plus organic manure (PAM + OM), straw mulching plus organic manure (SM + OM), buried straw plus organic manure (BS + OM), and bio-organic manure plus organic manure (BM + OM) were conducted to explore these linkages in newly reclaimed CTL in Jiangsu Province, eastern China. The results showed that the application of different soil reclamation treatments increased soil nutrient contents, pools, and modulated their stoichiometric ratio, which thus promoted the growth of oat. Soil under all reclamation treatments increased the contents of surface soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP), and the BM + OM treatment had the highest increase, which increased by 11.7–182.4%, 24.3–85.7%, 3.2–29.4%, respectively. The highest soil C pools were observed in the oat heading stage (36.67–41.34 Mg C ha−1), whereas the soil N and P pools were more stable during the oat growth period. Similarly, the highest surface soil C/N and C/P were observed in the oat heading stage (11.23–14.67 and 8.97–14.21), whereas the N/P in surface soil increased compared with the CK treatment during the oat growth period, with the exception of the filling stage. Land reclamation treatments significantly promoted oat growth by changing soil C, N, and P contents, pools, and stoichiometry, among which soil SOC, TN, TP, C/P, and N/P are more closely related to oat growth (p < 0.05).

Protecting Coastal Reclamation Area in Johor, Malaysia Through the Provision of Planning Documents

In Malaysia, the extension of coastal land relieves the pressure of demands for housing, commercial and industries despite the issues concerning development projects, including the inconsistency of provisions in statutory and non-statutory planning documents, jurisdiction area of Local Planning Authority and the role of Planning Authority. This study aims at investigating the application of statutory and non-statutory planning documents for coastal land reclamation projects through a local plan and a Comprehensive Development Plan. It employs a case study method using the Forest City in Johor as the study area. Expert Interviews provided primary data whilst secondary data encompassed various development plans, legal documents and policies related to coastal reclamation and planning. Results revealed the lack of provision for coastal reclamation area development plans notwithstanding the important roles of the Planning Authority. The study, therefore, suggests a revision of legislation and a review of development plans for the reclamation area.

Differential effects of various reclamation treatments on soil characteristics: an experimental study of newly reclaimed tidal mudflats on the east China coast

Reclamation of coastal land is increasingly being used as a means of raising agricultural productivity and improving food security in China. Applications of organic and inorganic supplements on reclaimed soils can significantly adjust a range of soil properties, C, N, P content and stoichiometry, and extracellular enzyme activities. However, the linkages between soil C꞉N꞉P stoichiometry and extracellular enzyme activities following reclamation of coastal saline soil remain largely unclear. In this experimental study, treatments included control (CK), chicken manure (OM), polyacrylamide plus chicken manure (PAM+OM), straw mulching plus chicken manure (SM + OM), buried straw plus chicken manure (BS + OM), and bio-organic manure plus chicken manure (BM + OM) were conducted to explore the linkages between soil physicochemical characteristics in reclaimed soils under different treatments and to evaluate their impact on oat yield. Soils under all reclamation treatments exhibited higher moisture content and, with the exception of SM + OM, lower soil pH compared to the control. The reclamation treatments also significantly decreased soil bulk density (BD) and soil salt content (SSC), and increased soil organic carbon (SOC), total nitrogen (TN) and organic phosphorus (OP). Our study of soil C꞉N꞉P stoichiometry revealed that newly reclaimed soils in the study area are N limited. Additionally, soil invertase (INV), urease (URE) and alkaline phosphatase (ALP) activity under different reclamation treatments were significantly enhanced compared with CK in surface soil, while soil catalase (CAT) activity was observed to be much higher in BM + OM than in other treatments. Mean oat yields for each of the treatments were ranked as follows: BM + OM > SM + OM > PAM + OM > BS + OM > OM > CK treatment. Our results also indicate that TN (12.1% and 12.4%) was the main factor affecting URE and ALP, whereas BD (13.5%) and pH (8.5) were key factors affecting INV and CAT activity, respectively.

Grain size and organic geochemistry of recent sediments in Lingding Bay, Pearl River Delta, China: implications for sediment dispersal and depositional processes perturbed by human activities

Lingding Bay (LDB), on the Pearl River Delta (PRD) of southern China, is a typical example of a large river mouth that is strongly affected by anthropogenic perturbations that have changed the boundary conditions of hydro- and sediment dynamic processes. An analysis of recent sedimentary patterns can shed light on the role of anthropogenic impacts on delta evolution. In this study, we collected surficial sediments from the LDB in December 2016 (dry season) and August 2017 (flood season) to analyze their grain size and organic geochemical compositions, with the aim of investigating recent depositional patterns in the bay and evaluating human impacts. The results reveal two major mud depocenters in the northeastern and southwestern parts of the bay, which are characterized by high values of grain-size end member 1 (EM1) and increased contributions of terrestrial organic carbon in the flood season. We propose that this sedimentary pattern is a manifestation of a system regime shift due to the strengthening of the fluvial function in fluvial-tide interactions and associated changes in the suspended sediment dispersal routine. We suggest that these changes are a result of recently intensified human activities, such as coastal land reclamation and sand mining. Coarsening of the surficial sediments in the LDB in the dry season and a marked increase in the terrestrial organic contribution at the mouth of the LDB indicates the redistribution of fine-grained sediments by waves and currents and increased mud export from the LDB in response to the shallowing of the bay.

Transport and fate of microplastics from riverine sediment dredge piles: Implications for disposal

Microplastics (MPs) are an environmental problem of growing concern. Aquatic sediments are considered as a final sink for MPs, but dredging can remobilize sedimentary MPs into both aquatic and terrestrial ecosystems. Although dredging is globally used for waterway deepening and ecological restoration, the environmental impacts of dredging on MP pollutants has not been previously assessed. In this study, Nile Red staining combined with micro-FTIR methods showed sediments containing high MP concentrations (6060–37610 n/kg·DW) from urban/suburban segments of a plain river network in Southeast China. The dredged sediments were stored in piles on farmlands, whereby MPs were subsequently dispersed to surrounding soils and surface waters while awaiting a permanent disposal option. MP concentrations in the soils surrounding the pile were higher in the dry season (wind dispersion), while MP concentrations in waters downstream of the piles were higher in the wet season (rainfall/runoff erosion). Whether dredge sediments are finally used to fertilize farmland, as fill material for coastal land reclamation or dumped into the ocean, MPs have the potential for remobilization into the environment causing concerns with aquatic food webs, agricultural production and human health. Therefore, disposal of dredge sediments containing MPs requires careful assessment to minimize potential environmental impacts.

Comparison of random forest and multiple linear regression models for estimation of soil extracellular enzyme activities in agricultural reclaimed coastal saline land

The alternations in soil physicochemical properties caused by the reclamation of coastal tidal land can strongly affect the activities of soil extracellular enzymes. Soil extracellular enzymes are one of the most active organic components in soil ecosystem, which is involved in almost all the biochemical reactions. Determining the importance of potential influencing factors of soil extracellular enzymes and thus estimating their activities are important for clarifying the biological mechanism of soil carbon and nitrogen cycling. In this study, the multiple linear regressions (MLR) and random forest (RF) models were conducted to estimate the activities of soil amylase and urease activities using covariates, such as soil water content (SWC), electrical conductivity (EC), total nitrogen (TN), total phosphorus (TP), and soil organic carbon (SOC) as well as the soil bulk density (BD) and pH. The results reveals that the amylase activity of fishpond was significantly higher than that of other land use types, while the urease activity of rape land, broad bean land, and fishpond were notably higher than that of bare flat, Spartina alterniflora, and uncultivated land. The RF model indicated that the SWC and TN is the main variable affecting amylase and urease activity, respectively. The RF model performed much better than MLR model in estimating the soil amylase and urease activity as it revealed much lower error indices (MAE and RMSE) and higher R2 value. The superiority of RF model in estimating amylase and urease activity is due to its advantages to handle the nonlinear and hierarchical relationships between enzyme activities and covariates, and insensitivity to overfitting and the presence of noise in the data.

Gaining or losing ground? Tracking Asia's hunger for ‘new’ coastal land in the era of sea level rise

Many coastal cities are short of land for development and, coupled with the need to mitigate the impact of extreme events against a background of ongoing sea-level rise, coastal land reclamation (CLR) has emerged as a frequently applied solution, most especially in Asia. However, the sustainability of these newly reclaimed lands under the combined onslaught of increasing population pressure, SRL, greater frequency of extreme events, and land subsidence is largely unknown. In order to assess the spatial extent and temporal trends in recent CLR projects, we mapped and tabulated the annual magnitude of change in coastal land gain from 1988 to 2018 for eight major Asian coastal cities. Across these cities, both the spatial extent and rate of CLR is remarkable; some 700 km2 has been reclaimed in just three decades. >35% of this new coastal land has been constructed in Shanghai alone (562 km2), while Singapore and Incheon have also experienced substantial land gains. These three cities alone account for almost 10% of all the land gained globally over the last three decades. An analysis of the spatio-temporal patterns reveals that, since recently reclaimed areas are predominantly characterized by construction, including ports, airports, commercial and residential uses, economic development is the most prominent driver. Shanghai, however, represents a significant departure from this trend, whereby >50% of the new coastal land gained during the recent past has not been devoted to construction projects and is vegetated, suggesting a different policy context. Commercial or otherwise, subsidence is widely reported as a major characteristic of recently reclaimed coastal land and is a major environmental challenge. Mapping recent rates of land subsidence over these newly reclaimed lands reveal that most are subject to significant levels of deformation, in the case of the international airport at Incheon, Republic of Korea, exceeding 25 cm annually.

Experimental Coastal Land Reclamation: Qianhai as a Case Interpreted

ABSTRACTInformed by a Coasian transaction cost paradigm enriched by the concept of Schumpeterian innovations, this paper discusses the advantages of using experimental coastal reclamation of the sea to build new cities with a policy for fostering innovations. A new development area at the margin of Shenzhen in China, Qianhai, is used to demonstrate how urban expansion by urban sprawling in a megacity can be avoided by reclamation of marginal land as analytically less costly than along intra-marginal land and more suitable for experimentation for the type of megacity concept that Qianhai aims to achieve.

Tendency of land reclamation in coastal areas of Shanghai from 1998 to 2015

Coastal land reclamation is one of the major human interventions in the coastal areas, it is a process undergo in many parts of the world. Land reclamation supplies land for development with urgent needs for coastal cities, and creates the opportunity for rapid urbanization, however, it also influences the integrity of the coastal ecosystem and results in a decline in biodiversity and ecosystem services. Over-exploitation and unreasonable use of coastal land has been a major issue and became a threat to ecological security in China. This paper analyzed the coastal land expansion and utilization process from 1980 to 2015 in Shanghai through remote sensing image processing and field investigations. The process of land reclamation in Shanghai and the effect of land use transformation on natural wetlands and the quality of the natural habitat are explored by analyzing land use and land cover change and modeling ecosystem services change by Integrated valuation of ecosystem services and tradeoffs (InVEST) model. The results show that the urban ‘ocean sprawl’ in Shanghai has increased by ∼10 % from 1980 to 2015 which transformed natural wetlands into construction land significantly. Despite strict control over the quality of reclamation projects and appropriate compensation with artificial wetlands, the natural habitat damage caused by reclamation increases exponentially in the past few decades. Recently the policies have changed from encouraging human reclamation to prohibit all kinds of land reclamation programs from national to local scales. It has major policy implications for future coastal habitat conservation. This paper gives an overview of the land reclamation in Shanghai and its impact on natural habitat that can foster the related policies to promote healthier and more reasonable urbanization during the economic transformation.

Mapping Trajectories of Coastal Land Reclamation in Nine Deltaic Megacities using Google Earth Engine

Increasing demand for land resources at the coast has exerted immense pressure on vulnerable environments. Population and economic growth in coastal cities have combined to produce a scarcity of suitable space for development, the response to which has frequently been the reclamation of land from the sea, most prominently in China. Urbanization is a key driver of such changes and a detailed investigation of coastal land reclamation at the city scale is required. This study analyzed remote sensing imagery for the period 1990 to 2018 to explore the trajectories of coastal land reclamation in nine major urban agglomerations across the three largest deltas in China using the JRC Global Surface Water (Yearly Water Classification History, v1.1) (GSW) dataset on the Google Earth Engine platform. The results are considered in the context of major national policy reforms over the last three decades. The analysis reveals that total land reclaimed among nine selected cities had exceeded 2800 km2 since 1984, 82% of which occurred after 2000, a year following the enactment of China’s agricultural ‘red line’ policy. Shanghai exhibited the greatest overall area of land extension, followed by Ningbo and Tianjin, especially in the period following the privatization of property rights in 2004. In analyzing annual trends, we identified the developmental stages of a typical coastal reclamation project and how these vary between cities. Scrutiny of the results revealed voids in nighttime light satellite data (2014–2018) in some localities. Although these voids appeared to be characterized by construction, they were occupied by vacant buildings, and were therefore examples of so-called “ghost cities.” In China, as elsewhere, continual land reclamation needs to be considered in relation to, inter alia, sea level rise and land subsidence that pose significant challenges to the vision of sustainable urban development in these three deltaic megacities.

The lives of women in a land reclamation project: Gender, class, culture and place in Egyptian land and water management

This article links feminist political ecology with the academic debate about commoning by focusing on the gendered distribution of common pool resources, in particular land and water. The research is set in the context of a coastal land reclamation project in Egypt’s Nile Delta, in a region where conflicts over resources such as arable land and fresh water are intensifying. Drawing on recent literature on commoning, we analyse the conditions under which different groups of resource users are constrained or enabled to act together. The article presents three case studies of women who represent different groups using land and water resources along the same irrigation canal. Through the concepts of intersectionality, performativity, and gendered subjectivity, this article explores how these women negotiate access to land and water resources to sustain viable livelihoods. The case studies unpack how the intersection of gender, class, culture, and place produces gendered subject positions in everyday resource access, and how this intersectionality either facilitates or constrains commoning. We argue that commoning practices are culturally and spatially specific and shaped by pre-existing resource access. Such access is often unequally structured along categories of class and gender in land reclamation and irrigation projects.

Assess Effectiveness of Salt Removal by a Subsurface Drainage with Bundled Crop Straws in Coastal Saline Soil Using HYDRUS-3D

The low permeability of soil and high investment of salt management pose great challenges for implementation of land reclamation in coastal areas. In this study, a temporary soil leaching system was tested in which bundled maize straw (straw drainage module, SDM) was operated as a subsurface drainage tube and diluted seawater was used for leaching. A preliminary field experiment was conducted in coastal soil-filled lysimeters to examine the system’s feasibility and a numerical model (HYDRUS-3D) based on field measured data was designed to simulate the entire leaching process. The simulation results showed that the soil water velocity and the non-uniformity of salt distribution were apparently enhanced in the region approaching the drain outlet. The mass balance information indicated that the amount of water drained with SDM accounts for 37.9–66.0% of the total amount of leaching water, and the mass of salt removal was about 1.7 times that of the salt input from the diluted seawater. Additional simulations were conducted to explore the impacts of the design parameters, including leaching amount, the salinity of leaching water, and the number of leaching events on the desalination performance of the leaching system. Such simulations showed that the salt removal efficiency and soil desalination rate both were negatively related to the seawater mixture rate but were positively associated with the amount of leaching water. Increasing the leaching times, the salt removal efficiency was gradually decreased in all treatments, but the soil desalination rate was decreased only in the treatments leached with less diluted seawater. Our results confirmed the feasibility of the SDM leaching system in soil desalination and lay a good foundation for this system application in initial reclamation of saline coastal land.

Applying Uncertain Science to Nature-Based Coastal Protection: Lessons From Shallow Wetland-Dominated Shores

Climate change and associated sea-level rise alongside the potential for alterations in the magnitude and frequency of extreme storm events, rapidly rising coastal populations, and a legacy of coastal land reclamation have led to the consideration of nature-based approaches towards coastal flood and erosion protection over recent years. The descriptions of such approaches highlight the flood protection value of natural coastal features but examples of their implementation remain few and far between and nature-based solutions to the rising coastal flood and erosion risk can certainly not (yet) be considered mainstream. One key problem around the implementation of these types of approaches has, arguably, been the relative lack of perceived scientific certainty, amongst stakeholders, surrounding the efficiency with which natural landforms reduce wave action on landward lying structures and the persistence of such landforms in an uncertain future. This makes nature-inclusive approaches less attractive to more traditional engineering-only approaches that rely solely on one ‘hard’ structure with a well-defined impact on waves and a specified design life. Using existing evidence for the coastal protection function of salt marshes, this paper offers a new perspective on this apparent lack of scientific certainty by offering a ‘no-regret’ application of existing science that allows decision makers and coastal planners to implement nature-inclusive approaches to coastal flood and erosion risk reduction measures with greater confidence.