Search Results (46)

Drawing on a case study from Ternate Island, a densely populated volcanic island in Eastern Indonesia, this research illustrates how multi-hazards and extreme weather events are likely to compound and cascade, with serious consequences for sustainable development in small island context. At the heart of Ternate Island sits the active Gamalama volcano, posing a constant eruption threat. Its location within the Ring of Fire further exposes the island to the risks of tsunamis and earthquakes. Additionally, the island’s physical features make it highly susceptible to flooding, landslides, and windstorms. Rapid urbanization has led to significant coastal alterations, increasing exposure to hazards. Ternate’s small-island characteristics include limited resources, few evacuation options, vulnerable infrastructure, and inadequate resilience planning. Combining GIS multi-hazard mapping with a structured survey in 60 villages in Ternate, this case study investigates the multi-hazard exposure faced by the local population and land coverage. The findings suggest significant gaps between village chiefs’ perceptions of the types of hazards and the multi-hazard assessment in each village. Out of 60 village chiefs surveyed, 42 (70%) are aware of earthquake risks, 17 (28%) recognize tsunami threats, and 39 see volcanoes as a danger. GIS assessments show that earthquakes could impact all villages, tsunamis could affect 46 villages (77%), and volcanoes could threaten 39 villages. The hazard map indicates that 32 villages are at risk of flash floods and 37 are at risk of landslides, and extreme weather could affect all villages. Additionally, 42 coastal villages on Ternate Island face potential extreme wave and abrasion disasters, but only 18 chiefs acknowledge extreme weather as a threat. The paper argues that addressing the cognitive biases reflected in the perceptions of community leaders requires transdisciplinary dialogue and engagement. Full article

Academic research plays a pivotal role in illustrating and testing potential future adaptation strategies to sea level rise in low-lying coastal communities and enhances local municipalities’ adaptation plans. In Waikīkī, Hawai‘i, the built environment is increasingly impacted by flooding from multiple drivers: sea level rise-induced direct marine inundation, storm-drain backflow, and groundwater inundation (GWI), compounded by high-wave runup, extreme tides, heavy rainfall, and a shallow groundwater table. Given Waikīkī’s economic and cultural importance, in-place accommodation of flooding is desired, yet implementation plans have not been developed. By combining current scientific research, urban design visualizations, and community feedback, the interdisciplinary research team advanced intentional communication between the many parties seeking increased flood resilience through the end of the 21st century. Site-specific architectural renderings were a key tool to prompt structured community input on the coordination, prioritization, policy, and feasibility of adaptation measures for buildings, utilities, transportation, and open space. Public outreach reports document that the majority of participants thought all adaptation strategies presented were applicable, especially relocating critical equipment in buildings and streets. Proposed methods to develop sea level rise-adjusted minimum building elevation requirements may inform local municipalities’ future codes to minimize coastal property damage. The multi-year iterative process fostered growing participation in hosted and invited events, further improving the publicly distributed research products. Full article

This study analyzed the distribution characteristics and sources of pollutants in the coastal estuaries of Zhanjiang Bay (ZJB) to provide theoretical and data support for the scientific prevention and control of bay pollution. Monitoring data from eight rivers and flood drains flowing into ZJB in March 2021 were used to analyze the composition and spatial distribution characteristics of polycyclic aromatic hydrocarbons (PAHs) and phthalate esters (PAEs) in the water bodies of the bay. The dominant components in the eight rivers and flood drains were 3–4-ring PAHs, with Bis (2-ethylhexyl) phthalate (DEHP), Diisobutyl phthalate (DIBP), and Dibutyl-O-phthalate (DBP) being the main PAE compounds. Higher pollutant levels were observed in residential areas, aquaculture zones, and industrial areas. Eigen-ratio analysis and principal component analysis were used to identify pollution sources, including atmospheric inputs (coal, petroleum products, biomass combustion products), offshore petroleum pollution, and plastic pollution sources. The assessment showed that atmospheric inputs contributed to 89.75% of the total PAHs in the bay, with coal and biomass combustion accounting for 62.12% and petroleum fuel combustion accounting for 27.63%. The content of ΣPAEs ranged from 588.43 to 1427.26 ng·L⁻¹, with a mean value of 906.59 ng·L⁻¹, which is at a low to medium level compared to other regions of China and abroad, indicating a medium-low level of pollution risk. The results of this study have important implications for guiding urban development, adjusting energy consumption structures, and planning pollution prevention and control measures in ZJB. Full article

The Puget Sound Coastal Storm Modeling System (PS-CoSMoS) is a tool designed to dynamically downscale future climate scenarios (i.e., projected changes in wind and pressure fields and temperature) to compute regional water levels, waves, and compound flooding over large geographic areas (100 s of kilometers) at high spatial resolutions (1 m) pertinent to coastal hazard assessments and planning. This research focuses on advancing robust and computationally efficient approaches to resolving the coastal compound flooding components for complex, estuary environments and their application to the Puget Sound region of Washington State (USA) and the greater Salish Sea. The modeling system provides coastal planners with projections of storm hazards and flood exposure for recurring flood events, spanning the annual to 1-percent annual chance of flooding, necessary to manage public safety and the prioritization and cost-efficient protection of critical infrastructure and valued ecosystems. The tool is applied and validated for Whatcom County, Washington, and includes a cross-shore profile model (XBeach) and overland flooding model (SFINCS) and is nested in a regional tide–surge model and wave model. Despite uncertainties in boundary conditions, hindcast simulations performed with the coupled model system accurately identified areas that were flooded during a recent storm in 2018. Flood hazards and risks are expected to increase exponentially as the sea level rises in the study area of 210 km of shoreline. With 1 m of sea-level rise, annual flood extents are projected to increase from 13 to 33 km² (5 and 13% of low-lying Whatcom County) and flood risk (defined in USD) is projected to increase fifteenfold (from 14 to USD 206 million). PS-CoSMoS, like its prior iteration in California (CoSMoS), provides valuable coastal hazard projections to help communities plan for the impacts of sea-level rise and storms. Full article

Coastal regions, increasingly threatened by floods due to climate-change-driven extreme weather, lack a comprehensive study that integrates coastal and riverine flood dynamics. In response to this research gap, we conducted a comprehensive bibliometric analysis and thorough visualization and mapping of studies of compound flooding risk in coastal cities over the period 2014–2022, using VOSviewer and CiteSpace to analyze 407 publications in the Web of Science Core Collection database. The analytical results reveal two persistent research topics: the way to explore the return periods or joint probabilities of flood drivers using statistical modeling, and the quantification of flood risk with different return periods through numerical simulation. This article examines critical causes of compound coastal flooding, outlines the principal methodologies, details each method’s features, and compares their strengths, limitations, and uncertainties. This paper advocates for an integrated approach encompassing climate change, ocean–land systems, topography, human activity, land use, and hazard chains to enhance our understanding of flood risk mechanisms. This includes adopting an Earth system modeling framework with holistic coupling of Earth system components, merging process-based and data-driven models, enhancing model grid resolution, refining dynamical frameworks, comparing complex physical models with more straightforward methods, and exploring advanced data assimilation, machine learning, and quasi-real-time forecasting for researchers and emergency responders. Full article

In low-lying coastal areas, the interplay of various factors including precipitation, river flow, and storm surge can lead to greater influence on floods when they occur simultaneously. The copula method was used in this study to investigate the bivariate flood risk of compounding storm surge and river discharge events in the Pearl River Delta (PRD). Our results indicate that while the correlation between storm surge and flood peak (S-Q) was weak, there was a strong dependence between the pairs of storm surge–flood volume (S-V) and storm surge–flood duration (S-D). For these three pairs, the Clayton copula was the optimal function for S-Q, while the Frank copula was the optimal function for S-V and S-D, respectively. When the flood volume exceeds 2.0 × 10⁴ m³/s and the flood duration is more than 10 days, the bivariate hydrologic risk for S-V and S-D is observed to decrease rapidly. Furthermore, the failure probability (FP) would be underestimated when the combined impact of river flow and storm surge is ignored in coastal flood risk assessment. Such bivariate hydrologic risk analysis implies that when determining design values in coastal flood risk assessment, the combined impact of river flow and storm surge should be taken into account. Full article

Understanding and quantifying the compounding effects of climate change, displacement and socio-vulnerability is crucial for the development and implementation of timely mitigation and adaptation policies. Here, we present a new Climate Displacement and Socio-Vulnerability (CDSV) score over NYC that accounts for several climate hazards (coastal and riverine flooding, heatwaves, hurricanes and winter weather), displacement and social vulnerability metrics with the ultimate goal of identifying those areas where risk of the combination of the three factors is the highest (e.g., hotspots due to compounding effects). To our knowledge, this is the first time that multiple climate hazards have been studied in conjunction with displacement and socio-vulnerability for NYC. We discuss those areas that are exposed to high CDSV values for the different hazards, where multiple hazards show overlapping high values of CDSV and analyze how socio-demographic characteristics have changed over the past two decades. We find that Black and Latin/Hispanic people are exposed to the compounding effects of multiple hazards, especially in areas located in the south Bronx, south Brooklyn and Queens, with maximum CDSV scores reaching values close to ~80 over a scale of 100, and with the increased exposure of Black, Latinx/Hispanix and Asians since the beginning of the century. We find that, except for the case of coastal flooding, the percentage of White people living in areas characterized by CDSV values decreases as CDSV scores increase where the percentage of Black people and Latin/Hispanic people increases, with the latter showing the strongest correlation. We also find a statistically significant relationship between the number of people with asthma and diabetes and the CDSV score in the case of heatwaves. Full article

The shape of the coast and the processes that mold it change together as a complex system. There is constant feedback among the multiple components of the system, and when climate changes, all facets of the system change. Abrupt shifts to different states can also take place when certain tipping points are crossed. The coupling of rapid warming in the Arctic with melting sea ice is one example of positive feedback. Climate changes, particularly rising sea temperatures, are causing an increasing frequency of tropical storms and “compound events” such as storm surges combined with torrential rains. These events are superimposed on progressive rises in relative sea level and are anticipated to push many coastal morphodynamic systems to tipping points beyond which return to preexisting conditions is unlikely. Complex systems modeling results and long-term sets of observations from diverse cases help to anticipate future coastal threats. Innovative engineering solutions are needed to adapt to changes in coastal landscapes and environmental risks. New understandings of cascading climate-change-related physical, ecological, socioeconomic effects, and multi-faceted morphodynamic systems are continually contributing to the imperative search for resilience. Recent contributions, summarized here, are based on theory, observations, numerically modeled results, regional case studies, and global projections. Full article

Flooding is a truly ubiquitous problem. Today, it puts an estimated 1.81 billion people at risk. Floods particularly affect coastal cities, where it is expected that the damage associated with inundations exceed the staggering value of USD 50 billion by 2050. Indeed, the risk associated with flooding in coastal cities is increasing due to three unequivocal trends: growing population in large urban centres, sea level rise, and increased intensity of extreme weather events. Planning and implementation of storm drainage systems in large cities is a complex, long, and expensive process. Typically, the effective lifespan of storm drainage systems may extend to nearly a century. Accordingly, such systems should be designed for the future, not the present. Addressing these important challenges, the paper evaluates flood risks in the coastal city of Maputo, in Mozambique. Results show that, although downtown Maputo is not particularly exposed to compound flooding, accounting for rainfall-tide events is essential to understand flooding in the area and evaluating the performance of the storm drainage system. Full article

Regarding global warming, the threat of flooding is projected to increase due to the change in intensity and frequency of single drivers and amplification caused by multi-driver interactions. This interaction becomes more complicated in developing regions with rapidly changing land cover. As a result, demands on flood risk management are rising especially in small watersheds, which are more vulnerable to driver disturbances compared with large watersheds. Existing studies focused on large watersheds rather than small watersheds. However, the findings derived from large-scale analysis cannot be transferred to small watersheds directly. This research investigated the flood responses in the Yonghe River Watershed (YRW) (63.8 km²) in Guangzhou, China, considering the impact of land cover change. The YRW experienced a disastrous compound flood on 22 May 2020. A hydrodynamic model integrating the Hydrologic Engineering Center’s Hydrologic Modeling System and River Analysis System (HEC-HMS and HEC-RAS, respectively) was established and calibrated using the inundation depths observed during the flood. Model analysis using multiple scenarios showed that the watershed is river-dominated, and flood responses to the three factors are nonlinear but with different increasing rates. The response curves for tide levels and land cover changes increase faster at high values, whereas the rainfall intensity curves vary slightly. These findings highlight the importance of integrating tidal impacts into flood risk management, even in river-dominated coastal watersheds. The study further recommends that in small watersheds, 50% imperviousness is an indicator of the urgent demand for flood risk management measures. Full article

Flooding is becoming more frequent along U.S. coastlines due to the rising impacts of fluvial and coastal flood sources, as well as their compound effects. However, we have a limited understanding of mechanisms whereby sea level rise (SLR) changes flood drivers and contributes to flood compounding. Additionally, flood mitigation studies for fluvial floodplains near tidal water bodies often overlook the potential future contribution of coastal water levels. This study investigates the role of SLR in inducing high-tide flooding (HTF) and compound flooding in a neighborhood that lies on a fluvial floodplain. Eastwick, Philadelphia, is a flood-prone neighborhood that lies on the confluence of two flashy, small tributaries of the tidal Delaware River. We develop a combined 1D-2D HEC-RAS fluvial-coastal flood model and demonstrate the model’s accuracy for low-discharge tidal conditions and the extreme discharge conditions of tropical Cyclone (TC) Isaias (2020) (e.g., Root Mean Square Error 0.08 and 0.13 m, respectively). Simulations show that Eastwick may experience SLR-induced HTF as soon as the 2060s, and the flood extent (34.4%) could become as bad as present-day extreme event flooding (30.7% during TC Isaias) as soon as the 2080s (based on 95th percentile SLR projections). Simulations of Isaias flooding with SLR also indicate a trend toward compounding of extreme fluvial flooding. In both cases the coastal flood water enters Eastwick through a different pathway, over a land area not presently included in some fluvial flood models. Our results show that SLR will become an important contributor to future flooding even in fluvial floodplains near tidal water bodies and may require development of compound flood models that can capture new flood pathways. Full article

Urban coastal flooding is a global humanitarian and socioeconomic hazard. Rising sea levels will increase the likelihood of hydrologic events interacting with high marine water levels. These compound events may, in turn, nonlinearly interact with urban infrastructure, potentially resulting in more extreme coastal flooding events. Here, an integrated Delft3D-FM based numerical modeling framework is used to concomitantly resolve multi-source flood processes (i.e., high marine water levels, precipitation) and infrastructure (e.g., seawalls, storm drains). Hydrodynamic model results are validated with embayment pressure sensor data and photographic observations from historical events. The impact of tide and precipitation phasing are examined. Multiple storm drain characterizations are presented and evaluated. Results show seawall and storm drain infrastructure is fundamental to accurately resolving spatial and temporal flood dynamics. Importantly, coastal management strategies such as raising seawall elevations to mitigate tidal flooding may exacerbate precipitation-based flooding in low-lying urban regions. Full article

Recent studies indicated that coastal green belts could not provide proper protection from extreme coastal flooding. Recent studies recommend employing a compound defense system of natural and artificial structures for extreme hazards. In this study, we introduce a new compound defense system consisting of coastal mangrove trees combined with reef ball modular structures. A series of laboratory experiments were conducted to investigate drag force reduction through the hybrid defense system. The hybrid defense system was subjected to a surge-type flow generated by a quickly lifting gate in a laboratory water tank. Within the experimental framework, the hydrodynamics of coastal flooding were described by the characteristics of the surge bore and the absorbed drag force. The obtained results show that the hybrid system effectively enhanced the absorbed bore drag forces and significantly improved the flow-damping performance. Full article

Like low-lying sandy coasts around the world, the Ghanaian coast is experiencing increasingly frequent coastal flooding due to climate change, putting important socioeconomic infrastructure and people at risk. Our study assesses the major factors contributing to extreme coastal water levels (ECWLs) from 1994 to 2015. ECWLs are categorized into low, moderate, and severe levels corresponding to the 30th, 60th, and 98th percentiles, respectively. Using these three levels over the Pleiades satellite-derived digital elevation model topography, potential flood extent zones are mapped. ECWLs have the potential to flood more than 40% of the study area, including socioeconomically important sites such as tourist beach resorts, Cape St. Paul lighthouse, and Fort Prinzenstein. In this study, all coastal flooding events recorded by the municipality of Keta fall within the 98th percentile category. Our results show a gradual increase in the frequency of flooding over the years. Flooding events are caused by a compound effect of the tide, sea level anomaly, waves, and atmospheric conditions. Finally, while wave run-up is the major contributor to coastal flooding, the tide is the one varying most, which facilitates a simple early warning system based on waves and tide but adds uncertainty and complicates long-term predictability. Full article

Estuaries worldwide are experiencing increasing threats from climate change, particularly from the compounding effects of sea level rise (SLR) and varying magnitude of river inflows. Understanding the tidal response of estuaries to these effects can guide future management and help assess ecological concerns. However, there is limited existing understanding on how estuarine tidal dynamics may respond to the compounding effects of SLR and altered riverine inflows in different estuaries. To partially address this knowledge gap, this study used data analysis and scrutinised idealised hydrodynamic models of different estuary shapes and boundary conditions to (i) identify broad effects of SLR on estuarine tidal dynamics under various river inflow conditions, (ii) determine how longitudinal cross-sections are impacted by these effects, and (iii) highlight some implications for environmental risk management. Results indicated that short- to moderate-length, high convergent estuaries experience the greatest and short- to moderate-length prismatic and low convergent estuaries experience the least variations in their overall tidal dynamics (i.e., tidal range, current velocity, and asymmetry). These variations were most evident in estuaries with large riverine inflows and macrotidal conditions. Compounding effects of SLR and altered riverine inflows induced spatially heterogenous changes to tidal range, current velocity, and asymmetry, with transects nearest to the estuary mouth/head and at a three-quarter estuary length (measured from estuary mouth) identified as the most and the least vulnerable zones, respectively. These findings provide an initial broad assessment of some effects of climate change in estuaries and may help to prioritise future investigations. Full article