Experimental Study of Overtopping on Sea Dikes and Coastal Flooding Under the Coupled Processes of Tides and Waves

Storm surges are cataclysmic natural disasters that occur along the coasts and are usually accompanied by large waves.The effects of coupled storm surges and waves can pose a significant threat to coastal security.Previous labo-ratory studies on the effects of storm surges and waves on coastal structures have typically utilized steady water levels and constant wave elements.An indoor simulation of the coupled processes of tides and waves is developed by adding a tide generation system to an existing laboratory wave basin to model continuous dynamic tide levels so that tide generation and wave-making occur synchronously in the pool.Specific experimental methods are given,which are applied to further study waves overtopping on artificial sea dikes and coastal flooding evolution under the coupled actions of tides and waves.The results of the overtopping discharge obtained by the test with a dynamic water level are compared with those obtained from steady water level tests and the existing empirical formula.In addition,the impacts of ecological coastal shelterbelts and structures on coastal flood processes and distributions are also investi-gated.The proposed simulation methods provide a new approach for studying the effects of storm surges and waves on coastal areas.The study also aims to provide a reference for coastal protective engineering.

Bibliometric Analysis of Global Research Progress on Coastal Flooding 1995–2016

Global research progress on coastal flooding was studied using a bibliometric evaluation of publications listed in the Web of Science extended scientific citation index. There was substantial growth in coastal flooding research output, with increasing publications, a higher collaboration index, and more references during the 1995–2016 period. The USA has taken a dominant position in coastal flooding research, with the US Geological Survey leading the publications ranking. Research collaborations at institutional scales have become more important than those at global scales. International collaborative publications consistently drew more citations than those from a single country. Furthermore, coastal flooding research included combinations of multi-disciplinary categories, including ‘Geology' and ‘Environmental Sciences & Ecology'. The most important coastal flooding research sites were wetlands and estuaries. While numerical modeling and 3 S(Remote sensing, RS; Geography information systems, GIS; Global positioning systems, GPS) technology were the most commonly used methods for studying coastal flooding, Lidar gained in popularity. The vulnerability and adaptation of coastal environments, their resilience after flooding, and ecosystem services function showed increases in interest.

Protective behaviors regarding coastal flooding risk in a context of climate change

The physical vulnerability of coastal areas due to rising sea level and the flooding risk consequent,does not guarantee the implementation of protective behaviors by these risk zones’inhabitants.This study aims to establish the link between the willingness to carry out protective behaviors and physical and perceived indicators of vulnerability.A typology of coastal flooding vulnerability,uses various physical indicators and their perceived counterparts which have been collected from 490 inhabitants of Cartagena(Colombia,declared world heritage of humanity by UNESCO in 1984),resident in areas of coastal flooding risks.The item-response theory(IRT)approach has been used.The results reveal that the implementation of protective behaviors is more related to perceived indicators,such as distance to the sea,than to actual physical vulnerability.We observe that physical vulnerability is linked to the intention to carry out protective behaviors.The presence of a defensive structure against coastal flooding could be considered as a visual cue and be a good predictor of the willingness to carry out protective behaviors.On the contrary,people in the most vulnerable situation(single-storey house)do not demonstrate a higher level of willingness to carry out protective behavior,as well of participants who lived in residential buildings which have demonstrated lower level of willingness to carry out such behaviors.Therefore,vulnerability of the house is not seen as a criterion that encourages participants to better protect themselves.

Modeling the Risks of Climate Change and Global Warming to Humans Settled in Low Elevation Coastal Zones in Louisiana, USA

This paper seeks to identify high risk areas that are prone to flooding, caused by sea level rise because of high impacts of global climate change resulting from global warming and human settlements in low-lying coastal elevation areas in Louisiana, and model and understand the ramifications of predicted sea-level rise. To accomplish these objectives, the study made use of accessible public datasets to assess the potential risk faced by residents of coastal lowlands of Southern Louisiana in the United States. Elevation data was obtained from the Louisiana Statewide Light Detection and Ranging (LiDAR) with resolution of 16.4 feet (5 m) distributed by Atlas. The data was downloaded from Atlas website and imported into Environmental Systems Research Institute’s (ESRI’s) ArcMap software to create a single mosaic elevation image map of the study area. After mosaicking the elevation data in ArcMap, Spatial Analyst extension software was used to classify areas with low and high elevation. Also, data was derived from United States Geological Survey (USGS) Digital Elevation Model (DEM) and absolute sea level rise data covering the period 1880 to 2015 was acquired from United States Environmental Protection Agency (EPA) website. In addition, population data from U.S. Census Bureau was obtained and coupled with elevation data for assessing the risks of the population residing in low lying areas. Models of population trend and cumulative sea level rise were developed using statistical methods and software were applied to reveal the national trends and local deviations from the trends. The trends of population changes with respect to sea level rise and time in years were modeled for the low land coastal parishes of Louisiana. The expected years for the populations in the study area to be at risk due to rising sea level were estimated by models. The geographic information systems (GIS) results indicate that areas of low elevation were mostly located along the coastal Parishes in the study area. Further results of the study revealed that, if the sea level continued to rise at the present rate, a population of approximately 1.8 million people in Louisiana’s coastal lands would be at risk of suffering from flooding associated with the sea level having risen to about 740 inches by 2040. The population in high risk flood zone was modeled by the following equation: y = 6.6667x - 12,864, with R squared equal to 0.9964. The rate of sea level rise was found to increase as years progressed. The slopes of models for data for time periods, 1880-2015 (entire data) and 1970-2015 were found to be, 4.2653 and 6.6667, respectively. The increase reflects impacts of climate change and land management on rate of sea level rise, respectively. A model for the variation of years with respect to cumulative sea level was developed for use in predicting the year when the cumulative sea level would equal the elevation above sea level of study area parishes. The model is given by the following equation: y = 0.1219x + 1944.1 with R square equal to 0.9995.

Preface for special section on coastal flood risk

Global concerns about changes in the world＇s climate have been well documented. The consequent impacts on coastal cities, agriculture, and coastal mariculture are difficult to quantify, but it is clear that there is a need for both better estimates of future climate and improved forecasting of storms and their impacts.

Modeling Integrated Coastal Flood Hazard in Hurricane Season

The manuscript proposed a procedure designed to determine the hazard of total coastal flooding during the impact of hurricanes, which uses in its formulation the combination of river flooding and that caused by marine upwelling, which is multiplied by a density factor of the water that finds an explanation for the effect is shielding and rising of the water level when the currents of both floods collide in the coastal zone. The application of the procedure experimentally in the coastal sector Sevilla, of the municipality Guama province Santiago de Cuba, resulting in the confirmation of areas previously modeled and estimated coastal flooding in the wake of extreme weather events in the study area;in addition to other new areas that confirm the actual visual and instrumental observations not included in previous studies.

Integrated Coastal Flood Risk Management as a Means to Build Resilient Communities

There is a clear trend in the increase of damages and loss of lives and livelihoods in coastal areas as a result of rapid increase in coastal populations, and overall socio-economic development in coastal regions resulting in an increase in vulnerability of populations exposed to coastal floods and exposed infrastructure. Coastal flooding as a result of i.e. storm surges are difficult to predict and cannot be prevented, however there are means to apply integrated flood risk management approaches aiming to reduce the impact of coastal floods. A measure of the effectiveness of such approaches is the awareness and response of coastal communities to coastal flood risks. The paper introduces best practices and methods to lower coastal flood risk at the level of provinces, districts and the community level. This includes advances in coastal flood forecasting and early warning practices, improvement of institutional preparedness and integrated flood management practices as well as measures at the community level aiming to strengthen their resilience to coastal floods. The paper provides a showcase for the historical development and achievements to pave ways for the eventual implementation of a pilot project on integrated flood risk management in coastal areas in central Viet Nam.

Application of SWAN+ADCIRC to tide-surge and wave simulation in Gulf of Maine during Patriot's Day storm

The southern coast of the Gulf of Maine in the United States is prone to flooding caused by nor＇easters. A state-of-the-art fully-coupled model, the Simulating WAves Nearshore （SWAN） model with unstructured grids and the ADvanced CIRCulation （ADCIRC） model, was used to study the hydrodynamic response in the Gulf of Maine during the Patriot＇s Day storm of 2007, a notable example of nor＇easters in this area. The model predictions agree well with the observed tide-surges and waves during this storm event. Waves and circulation in the Gulf of Maine were analyzed. The Georges Bank plays an important role in dissipating wave energy through the bottom friction when waves propagate over the bank from offshore to the inner gulf due to its shallow bathymetry. Wave energy dissipation results in decreasing significant wave height （SWH） in the cross-bank direction and wave radiation stress gradient, which in turn induces changes in currents. While the tidal currents are dominant over the Georges Bank and in the Bay of Fundy, the residual currents generated by the meteorological forcing and waves are significant over the Georges Bank and in the coastal area and can reach 0.3 m/s and 0.2 m/s, respectively. In the vicinity of the coast, the longshore current generated by the surface wind stress and wave radiation stress acting parallel to the coastline is inversely proportional to the water depth and will eventually be limited by the bottom friction. The storm surge level reaches 0.8 m along the western periphery of the Gulf of Maine while the wave set-up due to radiation stress variation reaches 0.2 m. Therefore, it is significant to coastal flooding.

A global analysis of coastal flood risk to the petrochemical distribution network in a changing climate

The global petroleum distribution network already faces a significant threat of disruption due to annual coastal flooding of major refining centers,which is expected to further increase with the effects of climate change.This study considers the impacts that sea level rise projections might have on the annual flood risk to coastal refineries,and how regional disruptions propagate across the network.Both the annual regional risk in terms of expected production disruption under a range of climate scenarios,as well as the expected production disruption due to a major flood event impacting refining hubs of high importance are assessed throughout the 21 st century.These risks are propagated across the network to model the global impact of coastal flood-induced refining disruptions.This analysis provides insights on the relative risks that different climate scenarios and flood events pose globally,informing potential mitigation and adaptation needs of critical facilities.Due to the highly interconnected nature of the global petroleum product distribution network,these results highlight the need for mitigation considerations for even regions with low domestic production disruption risk due to coastal flood hazards,as disruptions in remote regions can have cascading consequences resulting in significant disruption to petroleum product supply around the world.Furthermore,such results can inform decisions regarding technology transitions or energy diversification in light of the new understanding of climate risks to coastal refineries and the global petroleum distribution network.

COLLABORATIVE STRATEGIES FOR SEA LEVEL RISE ADAPTATION IN HAMPTON ROADS, VIRGINIA

The Hampton Roads region is located in southeastern Virginia where the Chesapeake Bay meets the Atlantic Ocean. The region includes seventeen municipal governments and has a large federal government presence with 26 federal agencies represented (See Figure 1). The region has a population that exceeds 1.7 million and is home to the deepest water harbor on the U.S. East Coast. Hampton Roads’ economy is dependent on the local waterways and houses the world’s largest naval facility, the sixth largest containerized cargo complex and supports a thriving shipbuilding and repair industry as well as a tourism industry. However, the region’s vast coastline also contributes to its vulnerability from climate change. Hampton Roads is experiencing sea level rise at twice the global rate with regional projections in the January 2017 National Oceanic and Atmospheric Administration (NOAA) report, Global and Regional Sea Level Rise Scenarios for the United States, of 1.9 feet of sea level rise at the low end and 11.5 feet of sea level rise under the most extreme case between 2000 and 2100 (NOAA, 2017). Planning for adaptation to sea level rise requires regional partnerships and strategies, especially for watersheds that cross municipal boundaries. While many of the municipalities in the region are forward thinking in their approaches to sea level rise, there is not a regional plan for adaptation and current federal funding models do not support analysis of and planning for sea level rise impacts on a regional scale. For coastal communities to be successful in sea level rise adaptation, there has to be a national understanding that water knows no borders and only collaborative problem-solving approaches that cross municipal boundaries will move regions toward adaptation. Functional boundaries of ecosystems or watersheds need to be the focus of adaptation rather than political boundaries of local, state, and federal entities. Coordination and collaboration between entities is the only way to achieve optimal outcomes.

The Impact of Large-Scale Reclamation on Hydro-Dynamic Environment--A Case Study of Xinghua Bay

A hydro-dynamic model is established on basis of MIKE21 FM to simulate the hydro-dynamic characteristics of Xinghua Bay and investigate the influence of reclamation project on the tidal elevation and tidal currents. Tidal elevation data was obtained at the six tide gauge stations around the Xinghua Bay, and another six current stations were established to observe the tidal current velocity and direction. Validation shows that the model-simulated tidal elevation and tidal currents agree well with observations made at different stations. Predictions are made according to the reclamation project proposed in the regional marine planning of Hanjiang Industrial Park around the port in Putian City. The variations of hydro-dynamic factors, such as tide, current velocity and direction and tidal influx are obtained, and the adverse effect of reclamation on marine environment is discussed. It is shown that the tidal level inside the Xinghua Bay during high tide decreases after the reclamation project is completed. The tidal currents during flooding tide generally decrease in the southeast of the reclamation region, with the maximum decreasing amplitude reaching 0.44 m s^(-1). On the other hand, the tidal currents during flooding tide increase around the southeast and southwest corners of the reclamation region. The tidal currents during ebb tide increase around the southeast and southwest corners of the reclamation region, with the maximum increasing amplitude attaining 0.18 m s^(-1). The results in this paper can give some guidance for the marine environment management and the effective utilization of land in Putian.

Flood Vulnerability Assessment Using Satellite Imagery Data

As flood extreme occurrences are projected to increase in intense and frequency due to climate change, the assessment of vulnerability and the identification of the most vulnerable areas, populations, assets and systems are an urgent need. Vulnerability has been widely discussed and several flood projection tools have been developed using complex hydrological models. However, despite the significant contribution of flood projection maps to predicting the impact of potential floods, they are difficult and impractical to use by stakeholders and policy makers, while they have proven to be inefficient and out of date in several cases. This research aims to cover the gaps in coastal and riverine flood management, developing a method that models flood patterns, using geospatial data of past large flood disasters. The outcomes of this research produce a five scale vulnerability assessment method, which could be widely implemented in all sectors, including transport, critical infrastructure, public health, tourism, constructions etc. Moreover, they could facilitate decision making and provide a wide range of implementation by all stakeholders, insurance agents, land-use planners, risk experts and of course individual. According to this research, the majority of the elements exposed to flood hazards, lay at specific combinations between 1) elevation (Ei) and 2) distance from water-masses (Di), expressed as (Ei, Di), including: 1) in general landscapes: ([0 m, 1 m), [0 km, 6 km), [0 m - 3 m), [0 km, 3 km)) and ([0 m - 6 m), [0 km, 1 km)), 2) in low laying regions: ([0 m, 1 m), [0 km, 40 km), [0 m - 3 m), [0 km, 30 km)) and ([0 m - 6 m), [0 km, 15 km)) and 2) in riverine regions: ([0 m, 4 m), [0 km, 3 km)). All elements laying on these elevations and distances from water masses are considered extremely and highly vulnerable to flood extremes.

Vertical accuracy assessment of freely available digital elevation models over low-lying coastal plains

The frequency of coastal flood damages is expected to increase significantly during the twenty-first century as sea level rises in the coastal floodplain.Coastal digital elevation model(DEM)data describing coastal topography are essential for assessing future flood-related damages and understanding the impacts of sea-level rise.The Shuttle Radar Topography Mission(SRTM)and Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM)are currently the most accurate and freely available DEM data.However,an accuracy assessment specifically targeted at DEMs over low elevation coastal plains is lacking.The present study focuses on these areas to assess the vertical accuracy of SRTM and ASTER GDEM using Ice,Cloud,and land Elevation Satellite,Geoscience Laser Altimeter System(ICESat/GLAS)and Real Time Kinematic(RTK)Global Positioning System(GPS)field survey data.The findings show that DEM accuracy is much better than the mission specifications over coastal plains.In addition,optical remote sensing image analysis further reveals the relationship between DEM vertical accuracy and land cover in these areas.This study provides a systematic approach to assess the accuracy of DEMs in coastal zones,and the results highlight the limitations and potential of these DEMs in coastal applications.

Using Multidisciplinary Analysis to Develop Adaptation Options against Extreme Coastal Floods

Long-term flood risk adaptation and decision making are complex because the future is full of deep uncertainties.Flexibility and robustness can be used to deal with future uncertainty.This study developed an integrated modeling framework that extends previous studies to the spatial domain to assess the future flood risks and the cost and benefit of three adaptation measures for four types of buildings in Shanghai.Real options analysis(ROA)and dynamic adaptive policy pathways(DAPP)were integrated to develop a dynamic adaptation pathway and identify robust adaptation options.The results show that:(1)Sea level rise and land subsidence will significantly exacerbate the flood risks in Shanghai;(2)Among the three flood control measures,wet-floodproofing has the best economic performance in terms of both the net present value and the benefit/cost ratio,followed by dry-floodproofing,and elevation;(3)Dryfloodproofing can be used at the beginning of the future period(2030–2100),and it can be replaced by wet-floodproofing in 2035–2042;the elevation measure also shows good performance at the beginning of implementation,but its performance will decline after 2041–2045;(4)The combined strategy of dry-and wet-floodproofing in 2044–2046and a hybrid strategy combining the three measures should be the optimal solution for reducing the flood risks in 2047–2051.The methodology developed in this study can provide insights for coastal cities to formulate cost-effective and feasible adaptation strategies in a deeply uncertain future.

Deficiency of Healthcare Accessibility of Elderly People Exposed to Future Extreme Coastal Floods:A Case Study of Shanghai,China

Socioeconomic development,subsidence,and climate change have led to high flood risks in coastal cities,making the vulnerable,especially elderly people,more prone to floods.However,we mostly do not know how the accessibility of life-saving public resources for the elderly population will change under future scenarios.Using Shanghai as a case,this study introduced a new analytical framework to fill this gap.We integrated for the first time models of coastal flooding,local population growth,and medical resource supply-demand estimation.The results show that under an extreme scenario of coastal flooding in the year 2050,in the absence of adaptation,half of the elderly population may be exposed to floods,the supply of medical resources will be seriously insufficient compared to the demand,and the accessibility of emergency medical services will be impaired by flooding.Our methodology can be applied to gain insights for other vulnerable coastal cities,to assist robust decision making about emergency responses to flood risks for elderly populations in an uncertain future.

Mapping floods due to Hurricane Sandy using NPP VIIRS and ATMS data and geotagged Flickr imagery

In this study,we present an approach to estimate the extent of large-scale coastal floods caused by Hurricane Sandy using passive optical and microwave remote sensing data.The approach estimates the water fraction from coarse-resolution VIIRS and ATMS data through mixed-pixel linear decomposition.Based on the water fraction difference,using the physical characteristics of water inundation in a basin,the flood map derived from the coarse-resolution VIIRS and ATMS measurements was extrapolated to a higher spatial resolution of 30 m using topographic information.It is found that flood map derived from VIIRS shows less inundated area than the Federal Emergency Management Agency(FEMA)flood map and the ground observations.The bias was mainly caused by the time difference in observations.This is because VIIRS can only detect flood under clear conditions,while we can only find some clear-sky data around the New York area on 4 November 2012,when most flooding water already receded.Meanwhile,microwave measurements can penetrate through clouds and sense surface water bodies under clear-or-cloudy conditions.We therefore developed a new method to derive flood maps from passive microwave ATMS observations.To evaluate the flood mapping method,the corresponding ground observations and the FEMA storm surge flooding(SSF)products are used.The results show there was good agreement between our ATMS and the FEMA SSF flood areas,with a correlation of 0.95.Furthermore,we compared our results to geotagged Flickr contributions reporting flooding,and found that 95%of these Flickr reports were distributed within the ATMS-derived flood area,supporting the argument that such crowd-generated content can be valuable for remote sensing operations.Overall,the methodology presented in this paper was able to produce high-quality and high-resolution flood maps over largescale coastal areas.