The residents of Sundarbans remain spirited in restoring their socio-economic conditions in a sustainable way facing the odds of climate change. Irrespective of religion, be it Hindu or Muslim, the residents, especially the forest goers, worship goddess Bonbibi, who is revered as the forest's guardian spirit. According to the myth, Bonbibi saves every individual from tigers, snakes, and crocodile attacks. The name "Bonbibi" is unique for any Bengali deity because the term "bibi" is frequently used by Muslim women as their surname. Such a location-based religious framing focuses on an original viewpoint that emphasizes ecological resilience as well as sustainable activities. Forest workers abstain from fish catching during specific breeding seasons and they do not obtain honey from the small flowering trees. The worship of the goddess Bonbibi promotes the benefits of protecting forests. It has been noted that Bonbibi, the personification of strong traits rather than spirituality, is worshipped for security rather than salvation. The people, especially the fishermen, Bauli (woodcutters), and Mouli (honey gatherers) pray, sing hymns, recite poetry, and seek the blessing of Goddess Bonbibi before entering the dense forest. The most astonishing thing about this is that Muslims still pray to Bonbibi like Hindus do, despite not believing in idol worship! Even after their husbands' deaths, the 'tiger widows' have unwavering faith in Bonbibi. In the Sundarbans, where death is largely unpredictable, it is clear how fear and vulnerability outweigh the differing perspectives of different religious communities and thus embody the humane principle of unity in diversity. In this way, the cultural ideals about the goddess Bonbibi are a fundamental component of the Sundarbans and may help address contemporary issues and reconstruct a resilient society. Since isolated set of scientific environmental protection policies would be insufficient to solve the issues raised by the vulnerable ecology, conservation guidelines protecting this largest coastal mangrove forest should acknowledge these location-based customary conventions.

How to cite: Basu, D.: Socio-cultural aspects foster resilience and religious unity in the Sundarbans, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-240, https://doi.org/10.5194/egusphere-egu23-240, 2023.

The Indian Sundarban has witnessed consecutive major cyclones (Cyclone Bulbul, Super Cyclone Amphan and Cyclone Yaas) in the 18 months between November 2019 and May 2021. Following Cyclone Yaas, the region also faced an extreme rainfall event. These extreme events have been compounded by the Covid-19 pandemic. This consecutive (and compound) hazard occurrence caused differential impacts based on varying levels of exposures and adaptive capacity of individuals. Examining the adaptive capacity of individuals within the context of consecutive hazards presents an opportunity to understand the ways in which adaptive capacity is drawn upon in disaster preparedness, response, and recovery actions, and how consecutive hazards with reduced return time affect the capacity of adaptive capacity to regenerate, with implications for risk levels. Since climate change is predicted to increase the intensity and frequency of cyclones, understanding where, when and with whom adaptive capacity needs to be supported is essential to reduce disaster risk in the Indian Sundarban delta. In-depth interviews were conducted with six men and six women of different socio-economic backgrounds from two community development blocks with different levels of exposure to cyclones (Sagar and Gosaba). Using the Local Adaptive Capacity Framework, this study reveals that adaptive capacities differ by gender and socio-economic background.  These different adaptive capacities were manifest in differential natures of preparedness, response, and recovery as undertaken by the respondents – and thus different levels of impact from cyclone and indirect Covid exposure. The increasing frequency and intensity of cyclones reduced the amount of time for adaptive capacity to replenish itself, hence there is an aggregated erosion of adaptive capacity, meaning that people are less able to absorb the impacts of cyclones that occur in quick succession relative to those that occur with a greater lag time. This study also includes co-produced adaptation measures which the respondents and the authors felt were needed for effective disaster risk reduction. These include structural interventions like raised concrete housing and resilient embankments, ecosystem-based adaptations like mangrove plantation and restoration especially in mudflats of fringe areas, livelihood-based adaptations like cultivation of saline-resistant crops, community based interventions like operation of community kitchens in the aftermath of disasters, importance of evacuation for all residents, and judicious relief distribution, and institutional adaptation including fair compensation. These findings add empirical weight to the concept of adaptation pathways, and highlight how the adaptation options available at any point in time are at least in part contingent on past circumstances. They also highlight the intersectional nature of adaptive capacity, which is important to inform policy and practice that equitably supports capacity to adapt. 

How to cite: Banerjee, S., Vincent, K., Chanda, A., and Ghosh, T.: Consecutive hazards and adaptive capacity of individuals – a gender-sensitive study in the Indian Sundarban delta, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8865, https://doi.org/10.5194/egusphere-egu23-8865, 2023.

How to cite: Gallop, S. L., Bryan, K. R., Hamilton, D. P., Foley, M., and Largier, J. L.: Restoration of estuary hydrological state with freshwater inflows: Non-linear processes, values-led decisions and multiple world views, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1213, https://doi.org/10.5194/egusphere-egu23-1213, 2023.

Chilika Lake on Odisha coast, India is the largest brackish water lagoon in Asia and the second largest world-wide. Spread over an area that varies from 906 sq. km. during the summer to 1165 sq. km in the rainy season, the lake is connected to the Bay of Bengal through a 32 km long and 1.5 km wide channel. A hotspot for biodiversity, it is one of the largest site for congregation of migratory birds, designated as the first Ramsar Site in India in 1981 and a Bird Sanctuary under India’s Wildlife Protection Act. However ecological degradation over the years has resulted in decline across several parameters including average area, water depth, and heavy siltation, imbalances in saline and freshwater combination (salinity gradient) with debilitating effect. The conditions are further worsened by mushrooming shrimp culture from the period of 1990’s which have threatened the ecological sustenance of the region including livelihood of over three lakh local community members who are directly or indirectly dependent on its eco-system (Sekhar, 2004; Pattnaik, 2007.

Odisha Government has launched several policy measures towards ecological conservation and a development strategy under Integrated Coastal Zone Management Plan (ICZMP) and using eco-tourism as a vehicle for growth.  As part of this, four tourism clusters are identified, and a master plan is under preparation for two of them; Rambha and Satapada-Sipakuda. The plan envisages significant investment from the private and public sectors to develop the region through eco-friendly hotels, resorts, camps, tourism infrastructure, water sports, recreational facilities etc.  Chilika region experiencing the combined effects of climate change and human induced alteration such as encroachment; its conditions are likely to further deteriorate with future projected climatic effects such as sea level rise.  The region was severely affected by two recent cyclonic storms; Cyclone Fani in 2019 and Phailin in 2013. Fani made a landfall over Chilika itself and in addition to causing massive damage and losses, opened up four more inlet mouths raising serious ecological concerns.

This study explores the extent to which the proposed tourism development of Chilika incorporates Disaster Risk Reduction (DRR) and Climate Change Adaptation (CCA) measures for an estuary carrying considerable ecological significance. It uses field data from Chilika region to highlight compartmentalized approaches and in the process overlooking scope for synergies. This approach of synthesizing DRR and CCA with Sustainable Development at a local level will be extremely useful to formulate appropriate development strategies not only for Chilika but also for similar social-ecological contexts for long term sustainability.    

Author: Biswanath Dash, Ph.D.

Bio: https://universe.bits-pilani.ac.in/hyderabad/biswanathd/Profile

Assistant Professor, K 131, Department of Humanities and Social Sciences,

BITS Pilani Hyderabad Campus, Hyderabad, Telengana-500078. India

Email: biswanath@hyderabad.bits-pilani.ac.in

Tel. 91-7036026393

N.U. Sekhar (2004) Fisheries in Chilika Lake: how community access and control impacts their management, Journal of Environmental Management, 73:257-266. doi:10.1016/j.jenvman.2004.07.006

Sarmistha Pattanaik (2007) Conservation of Environment and Protection of Marginalized Fishing communities of Lake Chilika in Orissa, India, Journal of Human Ecology, 22:4, 291-302, DOI: 10.1080/09709274.2007.11906037

How to cite: Dash, B.: Integration of DRR, CCA and Sustainable Development: Eco-Tourism for Chilika Lake, Odisha , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1666, https://doi.org/10.5194/egusphere-egu23-1666, 2023.

Marine plastic litter has become a serious global concern, which continuously plagues vulnerable countries and communities.  The Philippines has found itself as one of the top plastic polluters in the marine environment.  Its plastic waste problem has been documented in several studies; however, its implications are still unclear though a call for serious action is certain.  The existence of waste management practices adapted from a legal basis such as The Ecological Solid Waste Management Act of 2000 (known as the Republic Act No. 9003 or RA 9003) has greatly contributed to its call for action.  However, data from studies conducted to date suggests that the plastic waste problem is far from being addressed and is potentially starting to affect other environmental ecosystems such as mangrove ecosystems.  This study aims to assess the perception of the stakeholders on what ecosystem services the mangroves can offer and how this can benefit them.  Similarly, this seeks to examine what the community needs in order to mitigate improper plastic waste disposal especially in mangrove ecosystems.  A series of focus group discussions (FGDs) was conducted in 4 municipalities and 3 cities around the province of Cebu, Philippines. A total of 142 participants and representatives from the Academic, Business, Community, and Government (ABCG) sectors joined the activity. (ABCG model).  The results show that the people of Cebu province are more cognisant of the provisioning and regulating ecosystem services of mangroves than its support and cultural services.  One notable misconception among them is their view of mangroves as a filtering area where plastic wastes get trapped before going to the sea. Analysis on the behavioural factors influencing the people of Cebu province in the context of plastic waste management practices also show that Self-regulation>Risk influences them to manage their waste but Ability>Attitude>Norm has more weight in hindering them from practicing proper waste management.  This suggests a need for capability and capacity building interventions integrated in sound policy implementation that would encourage and empower the people to practice good plastic waste management on a more serious and consistent level especially in marine ecosystems. This study champions the ABCG model in this regard.

How to cite: Jones, G., Taboada, E., Paler, M. K., Balanay, P., Tagalog, S., and Orate, J.: Stakeholders’ Perception on Mangrove Ecosystem Services and Marine Plastic Waste Management in Cebu Islands, Philippines, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6312, https://doi.org/10.5194/egusphere-egu23-6312, 2023.

Physical and biogeochemical processes in coastal waters are shaped by salinity variation induced by river water mixing. As salinity is intrinsic to any aquatic ecosystem, any change will challenge the ecological framework. Thus, space-based monitoring of salinity in regions susceptible to salinity changes, such as estuaries and nearshore waters, is the need of the moment and supports Sustainable Development Goal 14 of the United Nations. Therefore, the salinity monitoring process addresses salinization/de-salinization issues of transitional waters. Current sea surface salinity products from satellites, such as Soil Moisture and Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP), exclude shallow waters, creating a salinity data gap in the land-ocean continuum. Such a gap in salinity considerably prevents continuous and synoptic river plume monitoring using satellite observations. Light absorption properties were studied in the coastal waters of Hudson Bay and James Bay, the shallow inland seas of Canada, to overcome the problem. River water carries terrestrial signals into the estuarine and coastal seas through dissolved organic matter (DOM) and inorganic sediments. DOM and sediments in seawater interact with the visible spectrum of solar radiation that can be mapped using ocean color remote sensing. Colored dissolved organic matter (CDOM), the optically active portion of DOM, dominates the light absorption budget at 412 nm in the coastal waters of Hudson Bay and James Bay, followed by the suspended inorganic solids. Hudson Bay waters were clearer relative to James Bay, with a higher content of river-sourced CDOM. The concentration of these river-derived optical tracers decayed offshore. CDOM underwent conservative dilution with increasing salinity, while suspended sediments were non-conservative. Therefore, based on the conservative CDOM and salinity relationship, a quantile regression approach was developed to quantify the Nelson River water dispersion in Hudson Bay using CDOM concentrations retrieved from moderate resolution imaging spectroradiometer (MODIS) images. This novel method permits the mapping of surface river water mixing with sea waters in terms of the distance from the river mouth corresponding to different percentages of diluted river water and the direction of river water transport. Such a strategy assists in coastal management, such as identifying the marine conservation area's geographic boundaries and conducting water quality tests to assess the health of coastal waters.

How to cite: Basu, A., McCullough, G., Bélanger, S., Doxaran, D., Sydor, K., and Barber, D.: Quantile regression of satellite-derived CDOM for river plume dispersion in southern Hudson Bay  , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9170, https://doi.org/10.5194/egusphere-egu23-9170, 2023.

This study investigates how both climatological and geophysical factors impact and have changed the landfast sea ice (LFI) regime in Hudson Bay and James Bay (HJB), Canada. LFI plays an important role in coastal land use practices, traditional livelihood and the formation of wetland ecosystems. Stability and extent of LFI platform is crucial to coastal communities as they use it for travel, fishing and hunting. The most vital concern raised in the Hudson Bay Summit 2022, was regarding the unpredictability of the LFI in terms of presence and thickness, which endangers the ecosystem services and livelihood of these coastal communities. The investigation relied on three sub-objectives: 1) trends of fast ice persistence and extent across HJB from 2001-2018; 2) impact of climatological factors on the landfast ice cycle, and 3) how coastal topography impacts the fast ice cycle. For this study we utilised an array of remote sensing and reanalysis products to study variables such as the landfast ice cycle (freeze-up, break-up) and persistence (CIS Ice charts, MODIS), air temperature (ERA5 reanalysis product), snow melt on land (MOD10A2 snow cover product), coastline orientation (Landsat) and coastal bathymetry (GEBCO). In addition to notable east-west contrast of the LFI climatology in HJB, the observations reveal how coastal topography impacts ice stability and extent, and eventually influences ice persistence, and how a positive feedback is created between the LFI and local air temperature. An understanding of these interlinkages are of critical importance to improve the prediction of LFI breakup in face of rapid climate warming and increased variability. The trends revealed through this study were unique compared to other Sub-Arctic regions with seasonal ice cover. Hence, a focused investigation of the factors that works as precursors of ice freeze-up and triggers break-up is proven to be vital to the continued safe use of the LFI platform.

How to cite: Gupta, K.: Role of climatological and geophysical controls on the landfast sea ice regime in the Hudson Bay region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9355, https://doi.org/10.5194/egusphere-egu23-9355, 2023.

Marine and coastal ecosystems are home to numerous plant and animal species, which all produce various valuable services for humans. The ocean has warmed unabated since 2005, continuing the clear multi-decadal ocean warming trends documented in the IPCC Fifth Assessment Report (AR5). Over the past decades, all scientific studies suggest that the oceans will continue to grow warmer and more acidic in the following decades. Even more alarming is the possibility that major ocean circulation patterns may disrupt the highly productive regions where upwelling brings nutrients from the deep waters of the ocean. The most key change in marine ecosystems associated with ocean warming has been coral-bleaching events. Often called “rainforests of the sea,” coral reefs are biodiversity “hotspots” and support an incredible array of flora and fauna. From 2016 that 31 per cent of tropical corals worldwide were already bleached.

Quantifying the value of natural capital and associated ecosystems, and representing the value of ecosystems in monetary terms, is crucial to envisage coastal management strategy. It is the first step toward coastal protection, enabling any meaningful cost-benefit analysis. Thus, effective mechanisms to translate these values into ecosystem protection strategies are essential, which are discussed in this paper.

Insurance, as a market-based financial instrument, has the potential to address some of the adaptation challenges related to safeguarding coastal and marine ecosystems. Designing an insurance product, for instance, to protect a coral reef system necessitates examining complex and dynamic interactions between exposure, hazard, and vulnerability.

With an 8,000-km long coastline, India has around 28 million workers in the fishing sector. The government, in 2020, introduced a draft National Fisheries Policy that offers insurance coverage but with several challenges and limitations. In India, the availability of quality marine data and enhancing the scope of marine and coastal insurance have the potential to address some of the challenges outlined above. This policy paper, with a focus on the global as well as Indian marine landscape, explores challenges around marine ecosystems and how insurance can play a role in adaptation to climate change and identify further areas of research.

How to cite: Basu, A. and Yadav, M. K.: The Landscape of Marine Ecosystem Challenges and the Role of Insurance in Climate Change Adaptation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12801, https://doi.org/10.5194/egusphere-egu23-12801, 2023.

Climate change has resulted in significantly more frequent precipitation extremes in many parts of the world. Latest research based on UK Climate Projections has suggested that short-term precipitation is projected to increase by 20% to 45% across the UK, providing more specific information compared to previous official guidance that used a single value for the whole UK. The impact of precipitation increase to surface water flooding has been evaluated based on statistical methods to some extent. However, most existing studies are not able to capture the physical process of flood dynamics although it is critical to understand the flooding process interacting complex built-environment during those highly transient extreme events to quantify the actual risk. This work investigates and quantifies impact of the change of rainfall on the spatial pattern of surface water flooding using a 2D hydrodynamic model to simulate designed rainfall events with climate change uplifts.  Flood depth and extent maps are produced in six cities/catchments across the UK against rainfall of different return periods to demonstrate potential change of surface water flood risk in future climate. The results translate the latest UK Climate Projections into intuitional flood risk changes and can be valuable to policy-makers and stakeholders to update policy and practice on surface water flood risk management, as well as providing new methodologies and tools.

How to cite: Ming, X., Liang, Q., Fowler, H., and Raven, E.: Hydrodynamic analysis of the impact of changes from precipitation extremes to surface water flooding in future climates, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7606, https://doi.org/10.5194/egusphere-egu23-7606, 2023.

This work has implemented An Integrated Disaster Risk Management IDRiM approach on the disaster events of Indian Sundarbans, a world heritage site where the ecosystem and livelihood are threatened by frequent cyclonic disasters originating in Bay-of-Bengal. The inhabitants encounter tremendous economic losses as well as losses of lives due to direct cyclonic storms and the storm surge water flooding. In recent past, the forestry and aquaculture dependent economically backward inhabitants of Sundarbans experienced the devastating hit of Sidr (2007), Aila (2009), Phailin (2013), Hudhud (2014), Bulbul (2019), Amphan (2020), Yaas (2021), Sitrang (2022) which left them with severe losses.  The habitants started to change their work pattern and intended to migrate toward the mainland. Land use / land cover also changed with some changing scenario of the mangrove ecosystem.

All these adverse effects of the coastal cyclonic events claim the need for a proper and effective disaster damage reduction plan. Here, the proposal has been given to formulate a web-enabled platform for near real-time cyclonic path and surge height prediction and rescue and rehabilitation planning with the stakeholders to make the execution effective and successful. This is a platform where; various government departments will update the cyclone related earth observation and hydro-meteorological data on near real-time basis during the emergency period. Ground information and infrastructural spatial database are to be regularly updated by the concerned departments. The access to the platform will be secured to the planners and stakeholders whereas a selective accessibility can be allowed for the community people for community awareness and live situation tracking. The purpose is to minimize the loss as much as possible by taking prompt actions by the administration. The platform also helps to monitor the disaster preventive measures with the hand-to-hand cooperation of local people and administration. In some cases, administration needs the authentication of the relief claims which can increase the transparency of the government strategies and schemes. Rehabilitation management can be more effective where the temporal high resolution remote sensing optical data as well as high resolution surface elevation data with the predicted flood risk zones can be accessed. Pre and post event temporal dataset are to be incorporated in the platform for recovery and reconstruction management. Thus, this platform can effectively minimize the adverse impact of coastal cyclonic disaster by the participation of community, stake holders and the planners.

Key-words: community-based capacity, Integrated Disaster Risk Management, storm surge water flooding, web-enabled platform, participation of community.

How to cite: Laha Salui, C.: INTEGRATED DISASTER RISK MANAGEMENT (IDRiM) APPROACH FOR COASTAL AREAS USING PARTICIPATORY GIS: A CASE STUDY OF INDIAN SUNDARBANS, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7969, https://doi.org/10.5194/egusphere-egu23-7969, 2023.

The feasibility of reducing nutrient pollution impacts by redirecting excess nutrient flux away from the photic zone is investigated. Alternate effluent discharge strategies to avoid or bypass the euphotic zone were tested under the hypothesis that in deep estuaries, depth of the surface exchange outflow layer may be greater than euphotic zone depth, providing opportunity for a fraction of the nutrient pollution to be exported out passively. We used the Salish Sea region in the Pacific Northwest as a test bed for this assessment. Euphotic zone depth in the Puget Sound basin of Salish Sea in U.S waters varies from 8 m to 25 m while the depth of outflow layer is approximately 60m. Sensitivity of biological response and water quality impact were quantified using an established biophysical model of the system, using exposure to low DO levels as the metric (< 2 mg/L hypoxia and < 5 mg/L impairment). Opportunity to reduce nutrient pollution impact was tested through outfall relocation strategies, applied to 99% of the anthropogenic loads currently delivered to the Puget Sound. The results show that relative to natural impairment levels, marine wastewater outfalls are responsible for 36% of increase, while loads from upstream watersheds that enter Puget Sound via river flows, are responsible for 70% of increase in impairment. Results were consistent with the hypothesis in that moving the outfalls to deeper waters resulted in reduced primary production. However, in some basins, the benefits of lower water column respiration were offset by reduced DO production and were accompanied by some loss in the strength of circulation. Puget Sound basin results indicate worsening of DO impairment hours (average +3.0%), while Whidbey Basin showed improvement in DO impairment hours (-6.8%) relative to existing conditions. The results indicate that presence of multiple sills and the associated reflux flows / circulation obstruct the export of nutrients out of the system. The efforts to relocate outfalls to achieve euphotic zone bypass and improve DO impairment were therefore not as effective as hypothesized.

How to cite: Khangaonkar, T., Yun, S. K., and Premathilake, L.: Nutrient pollution impact reduction assessment in a deep estuary, euphotic zone avoidance/bypass considerations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9670, https://doi.org/10.5194/egusphere-egu23-9670, 2023.

Seagrass meadows provide many valuable global ecosystem services including blue carbon sequestration, and habitat and nursery ground provisioning for commercial fish. Yet, the conservation, research and monitoring of these highly productive habitats are hampered by a notable lack of spatially-explicit knowledge in many parts of the world, including the Seychelles. As an archipelagic state, a sizeable portion of the Seychellois Nationally Determined Contributions and thus carbon stocks are “blue”, owing to the therein intertidal and subtidal seagrasses.

Due to the subtidal seagrass living on the seabed, the dominant spaceborne remote sensing approach is optical. However, owing to the atmospheric conditions and persistent cloud cover over tropical regions, it is sometimes difficult to find a suitable, cloud-free and glint-free image. In order to maximise use of every relevant and useful pixel without discarding them due to a partial cloud cover, we employ a multitemporal image composition approach, which concurrently reduces some of the effects of sunglint and cloud shadows. However, a multitemporal approach on a national scale is computationally expensive and requires much resources.

Here we present the Global Seagrass Watch coastal Ecosystem Accounting framework, which harnesses the powerful cloud computing Google Earth Engine (GEE) platform to process the satellite images across a large spatial and temporal scale. Furthermore, with the addition of the Planet & Norway’s International Climate and Forests Initiative (NICFI) onto GEE, anyone can have free access to the 4.77 m high spatial resolution PlanetScope image composites between 2015 to present. Although terrestrially-focused, the presence of shallow waters within the buffered coastline in these composites allows the exploitation of NICFI for coastal aquatic remote sensing, as well. Consequently, a potentially high-resolution, large-scale seagrass map could be produced with savings in time and cost.

In this study, we implement our multitemporal composition approach on GEE onto the PlanetScope composite archive in order to map and estimate the area of the seagrass meadows of Seychelles on a national level.

The results will contribute to the development of a national seagrass mapping and monitoring blueprint monitoring system, which is important for the assessment of national seagrass blue carbon stocks for the Nationally Determined Contributions for Seychelles, as well as beyond.

How to cite: Lee, C. B., Martin, L., Traganos, D., Rowlands, G., and Reinartz, P.: See Seagrass from Space: From Analysis-Ready PlanetScope Satellite Imagery to Nationwide Seagrass Maps for the Nationally Determined Contributions of Seychelles, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12753, https://doi.org/10.5194/egusphere-egu23-12753, 2023.

Deltas and estuaries concurrently represent some of the most delicate natural environments and highly populated regions of the world. Due to climate change, among other global and local variables (e.g., urbanization, land subsidence, etc.), these areas face unprecedented increases to flood risk over the next several decades. A large portion of total future coastal flood risk is found in the world's deltas and estuaries, while overall global riverine flood risk exhibits more expansive spatial distribution. Still, the presence of high levels of potential human and monetary impacts due to these two types of flooding presents a unique challenge for decision makers worldwide. For these areas of the world to survive, disaster risk reduction action is needed in the form of adaptation. Our work shows the adaptations options for a selection of critical deltas and estuaries throughout the world. We model dykes and levees (structural hazard reduction), saltmarsh preservation and mangrove restoration (nature-based hazard reduction), dry-proofing of urban assets (vulnerability reduction), and zoning restrictions on future urban development (exposure reduction), and quantify the costs and benefits of these adaptation measures. Certain adaptation measures are better suited for some cases depending on the income level, environmental characteristics, and spatial population distribution of the region in question. For example, in the Ganges delta, expanding mangrove forests proves to be the most cost beneficial adaptation strategy. Meanwhile, restricting future urban development away from floodplains in the Congo estuary shows the most potential for flood risk reduction due to large amounts of projected population growth. And highly urbanized deltas and estuaries, such as the Mekong and the Hudson, demonstrate potential risk reductions via widespread dry-proofing. With this work, we are able to identify specific adaptation pathways forward into the future for these crucial areas of the world, while also opening the dialogue for related topics, such as compound flood risk and adaptation hybridization.

How to cite: Mortensen, E. and Ward, P.: Adapting with future increases to coastal and riverine flood risk in deltas and estuaries: a global perspective, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14131, https://doi.org/10.5194/egusphere-egu23-14131, 2023.

With global climate change and sea level rise, the frequency and strength of coastal hazards are increasing. Nature-based solutions have been recognized as a kind of sustainable approach to coastal protection. Among them, mangroves play a crucial role in attenuating coastal waves, tides, and storm surges. From top to bottom, mangrove trees have a typical three-layered structure, consisting of leafy canopies, thick trunks, and intertwined roots. Most previous studies investigating mangrove-wave interaction oversimplified mangroves as rigid cylinders. In this way, the effects of the vertical morphology structure of mangroves on wave decay are ignored and have not been fully understood. To bridge this knowledge gap, we carried out a series of flume tests to compare the differences in the wave attenuation ability of artificial near-natural mangrove models and rigid cylinder models. The wave damping factor was calculated based on fitting the measured wave height evolution through the mangrove zone to the wave decay formula proposed by Dalrymple et al. (1984). It has been observed that the submerged mangrove canopies significantly enhanced the wave attenuation rate. To unify the correlations between the wave decay parameter and the varying submerged mangrove volumes under different waves and water depths, we proposed a new parameter, the hydraulic submerged volume index (HSVI), to quantify the wave damping contributions by mangrove canopies, stems, and roots respectively. A fitted linear correlation between the HSVI and wave damping factor was induced. Then the bulk drag coefficient versus nondimensional hydraulic parameters, i.e. Reynolds number Re, Keulegan-Carpenter number KC, and Ursel number Ur, were discussed in detail, and modified correlations considering the effects of varying characteristic length scales of nondimensional hydraulic parameters were proposed.

How to cite: Zhang, R., Lei, J., and Chen, Y.: Laboratory study on wave attenuation by submerged mangrove canopies, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16646, https://doi.org/10.5194/egusphere-egu23-16646, 2023.

Abstract

The education sector experiences catastrophic effects of hazards in the form of life losses and school infrastructure damage. Safety of children at school is a global priority, which has also been stressed in the Hyogo Framework for Action (2005-2015) as well as Sendai Framework for Disaster Risk Reduction (SFDRR, 2015-2030). Involvement of school children in disaster risk reduction (DRR) initiatives at the local, regional, and global levels is of paramount importance for resilience development in school education. This research aims to explore the impacts of multiple hazards and associated disruptions in school education, and attempts to identify determinants of resilience of school education to multiple hazards. The various stressors of school education vulnerability will be highlighted through impact chain modeling, which will help in identification of gaps in preparedness of school communities and hence will contribute as a reference for disaster management teams and school communities for better response strategies. The impact chain assessment will be performed through the VenSim model to estimate the degree of cascading impacts on other infrastructure and interdependent systems. The input variables will be defined through the outputs of assessment of climate and anthropogenic stressors for school education vulnerability as well as the evaluation of relationships between social vulnerability and school education.    

Keywords: Sundarbans Delta, Climate Hazard, Education System Vulnerability, Impact Chain.

How to cite: Pal, A., Tsusaka, T. W., Sundaram, M., Ahmad, M. M., and Nguyen, T. P. L.: Impact Chain Assessment for Vulnerability of the School Education System to Climate Hazards in the Sundarbans Delta, India, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-877, https://doi.org/10.5194/egusphere-egu23-877, 2023.

The Philippines has one of the longest coastlines in the world, spanning 36,289 kilometers in its over 7,100 islands. Of that length, around 60 kilometers is inhabited by fishing communities whose socio-economic activities depend primarily on the coastal areas. Over two million registered fishing communities engage in the fishery and other aquaculture-related activities. The country's fishing industry continues to contribute positively to the country’s Gross Domestic Product (GDP). With its rich biodiversity, the Philippines produced around 1.21 MT of fisheries products from commercial and municipal fishing and aquaculture activities, amounting to PhP92.59 billion in the second quarter of 2022.

Despite the significant contribution of the fishing industry to the country’s economic growth, the fishing communities that form the very backbone of industry are considered part of the vulnerable population. With the country plagued by an average of 20 typhoons annually and roughly 8 or 9 making landfall, fishing communities are perpetually displaced, and their livelihood disrupted. This, alongside unsustainable coastal development practices in the fishing sector, has aggravated the growing problem. Through a comprehensive review of literature, the study will assess the vulnerability of fishing communities to coastal hazards and recommend development planning interventions to increase their resilience.

Key words: coastal hazards, fishing community, planning, livelihood, sustainability  

How to cite: Castro, A. G. and Magnaye, D.: Coastal Hazards and the Challenges for Planning Fishing Communities in the Philippines, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-885, https://doi.org/10.5194/egusphere-egu23-885, 2023.

Waves are one of the essential factors triggering disastrous hazards in coastal and estuary areas. Simulation and understanding of their propagation process from deep water to nearshore are important for management and protection of coastal regions. Development of nonhydrostatic models has received increased attention in recent years and depth-integrated nonhydrostatic models have been widely used in large-scale applications. However, most existing depth-integrated nonhydrostatic models neglect the vertical advection and dissipation terms in the vertical momentum equation and assume linear distribution of pressure and flow velocities. These simplified equations are therefore not able to depict the physical details of certain wave dynamics,  prohibiting the application in wave prediction in relative deep water.

This paper adopts the quadratic polynomials to describe both the pressure and velocity terms to improve the linearity and nonlinearity accuracy of the formulation. As the derived nonhydrostatic wave equations involve only the first- and second-order spatial derivatives and are formulated at a similar frame to the previous depth-integrated models, they can be numerically solved using the standard numerical schemes adopted in the previous models. Specifically, a fractional step method is adopted to divide the numerical solution procedure into the hydrostatic and nonhydrostatic steps. A second-order MUSCL-Hancock Godunov-type scheme is employed in the hydrostatic step to obtain the temporary solution; then a finite difference method is used in the nonhydrostatic step to calculate the hydrodynamic pressure by solving the Poisson's equation to achieve the final numerical solution over a full time step. The proposed model is validated against a series of experiment tests. Higher solution accuracy is confirmed by comparing the simulation results with those produced by existing depth-integrated nonhydrostatic models.

Keywords: Nonhydrostatic Model; Coastal Hazards; Finite-Volume Method; Finite-Difference Method; Wave Propagation

How to cite: Wang, H., Wang, G., and Liang, Q.: A novel coastal wave model with improved nonhydrostatic equations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4672, https://doi.org/10.5194/egusphere-egu23-4672, 2023.