coastal resilience engineering unit 3 study guides

Key Concepts and Definitions

• Sea level rise (SLR) the increase in the average level of the Earth's oceans over time, primarily due to thermal expansion of water and melting of land-based ice
• Eustatic sea level change global changes in sea level caused by alterations in the volume of water in the oceans, often due to ice melt or changes in ocean basin volume
• Relative sea level change local changes in sea level relative to the land surface, influenced by factors such as land subsidence, uplift, and ocean circulation patterns
• Coastal vulnerability the susceptibility of coastal areas to the adverse impacts of sea level rise, such as flooding, erosion, and saltwater intrusion
• Adaptation strategies actions taken to adjust to the actual or expected impacts of sea level rise, aiming to reduce vulnerability and increase resilience
  • Includes hard engineering solutions (seawalls, levees) and soft approaches (beach nourishment, wetland restoration)
• Resilience the ability of a system to absorb disturbances while retaining its basic structure and function, and to adapt and evolve in response to changing conditions
• Coastal squeeze the loss of coastal habitats, such as beaches and wetlands, due to the combined effects of sea level rise and hard coastal defense structures that prevent landward migration

Causes of Sea Level Rise

• Thermal expansion of oceans as water expands when it warms, it takes up more space, contributing to sea level rise
  • Accounts for about 50% of the observed global mean sea level rise since 1900
• Melting of land-based ice such as glaciers, ice caps, and ice sheets (Greenland and Antarctic) adds water to the oceans
  • Greenland ice sheet loss has accelerated in recent decades, contributing ~0.7 mm/year to global sea level rise
  • Antarctic ice sheet loss, particularly from the West Antarctic Ice Sheet, is a growing concern due to its potential for rapid disintegration
• Changes in land water storage human activities like groundwater extraction, dam construction, and irrigation can influence sea level by altering the amount of water stored on land
• Vertical land motion subsidence (sinking) or uplift of the land surface can affect relative sea level
  • Subsidence due to groundwater extraction, oil and gas extraction, and sediment compaction exacerbates relative sea level rise in many coastal cities (Jakarta, New Orleans)
• Gravitational effects the redistribution of mass from melting land-based ice alters Earth's gravitational field, causing regional variations in sea level rise
• Ocean circulation changes shifts in ocean currents and wind patterns can lead to regional differences in sea level rise

Measuring and Projecting Sea Level Rise

• Tide gauges measure relative sea level change at specific locations along the coast
  • Provide the longest records of sea level change, with some dating back to the 18th century
  • Affected by vertical land motion, requiring careful interpretation
• Satellite altimetry measures absolute sea level change globally using radar to determine the distance between the satellite and the ocean surface
  • Provides near-global coverage and high spatial resolution since the early 1990s
• Gravity Recovery and Climate Experiment (GRACE) satellite mission measures changes in Earth's gravity field, which can be used to estimate changes in land ice mass and ocean mass
• Paleoclimate records (coral reefs, salt marshes, ice cores) provide information on past sea level changes over longer timescales
• Climate models project future sea level rise based on different greenhouse gas emission scenarios and climate system responses
  • Intergovernmental Panel on Climate Change (IPCC) provides regular updates on sea level rise projections
  • Under high emission scenarios, global mean sea level could rise by 0.6-1.1 m by 2100

Coastal Impacts and Vulnerabilities

• Increased coastal flooding more frequent and severe flooding during high tides, storm surges, and extreme weather events
  • Low-lying coastal areas, such as deltas and small island states, are particularly vulnerable
• Coastal erosion accelerated loss of beaches, dunes, and cliffs due to higher water levels and more intense wave action
  • Can lead to loss of coastal infrastructure, property, and ecosystems
• Saltwater intrusion the movement of saline water into freshwater aquifers, rivers, and wetlands, affecting water resources and ecosystems
  • Poses risks to coastal agriculture, water supply, and biodiversity
• Habitat loss and degradation sea level rise can submerge or alter coastal habitats, such as wetlands, mangroves, and coral reefs
  • Coastal squeeze limits the ability of habitats to migrate landward in response to rising seas
• Impacts on coastal infrastructure and assets ports, harbors, roads, and buildings are vulnerable to flooding, erosion, and structural damage
  • Adaptation and protection measures can be costly and may have limited effectiveness over the long term
• Socioeconomic impacts displacement of coastal communities, loss of livelihoods (fishing, tourism), and increased exposure to natural hazards
  • Disproportionate impacts on vulnerable populations, such as low-income communities and indigenous peoples

Adaptation Strategies and Engineering Solutions

• Coastal protection hard engineering structures designed to protect the coastline from erosion and flooding
  • Seawalls, levees, and dikes provide a physical barrier against rising seas and storm surges
  • Breakwaters and groins reduce wave energy and trap sediment to stabilize the shoreline
• Nature-based solutions the use of natural systems and processes to reduce coastal vulnerability and enhance resilience
  • Beach nourishment the addition of sand to widen beaches and provide a buffer against erosion and flooding
  • Wetland restoration the rehabilitation of degraded wetlands to improve their capacity to absorb floodwaters, trap sediment, and provide habitat
  • Living shorelines the use of natural materials (oyster reefs, vegetation) to stabilize the shoreline and create habitat
• Managed retreat the planned relocation of people, assets, and activities away from high-risk coastal areas
  • Allows for the natural landward migration of coastal ecosystems in response to sea level rise
  • Requires careful planning, community engagement, and support for displaced populations
• Accommodation measures that allow for the continued use of coastal areas while adapting to the impacts of sea level rise
  • Elevating buildings and infrastructure to reduce flood risk
  • Updating building codes and land-use regulations to guide development in vulnerable areas
  • Improving early warning systems and emergency response plans
• Integrated coastal zone management a holistic approach that balances the environmental, social, and economic aspects of coastal management
  • Involves stakeholder participation, adaptive management, and long-term planning
  • Considers the interactions between different sectors (fisheries, tourism, conservation) and the cumulative impacts of multiple stressors

Case Studies and Real-World Examples

• The Netherlands a country with a long history of coastal protection and adaptation, given its low-lying topography
  • The Delta Works a series of dams, sluices, and storm surge barriers constructed after the 1953 North Sea flood
  • Room for the River program a shift towards nature-based solutions, giving rivers more space to flood safely
• Venice, Italy a city facing increasing flood risk due to sea level rise and land subsidence
  • MOSE (Modulo Sperimentale Elettromeccanico) project a system of mobile floodgates designed to protect the city from high tides and storm surges
  • Challenges with cost, maintenance, and environmental impacts
• Small Island Developing States (SIDS) countries that are particularly vulnerable to sea level rise due to their low elevation, small size, and limited resources
  • Maldives investing in coastal protection measures, such as seawalls and breakwaters, to protect critical infrastructure and tourist resorts
  • Kiribati exploring options for managed retreat and international migration as a long-term adaptation strategy
• United States various coastal states and cities are developing adaptation plans and implementing projects to address sea level rise
  • Louisiana Coastal Master Plan a 50-year plan that includes wetland restoration, sediment diversion, and structural protection measures
  • Miami Beach, Florida investing in stormwater management, beach nourishment, and elevated roads to combat flooding and erosion

Economic and Social Implications

• Adaptation costs the financial resources required to implement coastal protection, accommodation, and retreat measures
  • Estimates vary widely depending on the scale, location, and type of adaptation measures
  • Developing countries and small island states may face significant financial barriers to adaptation
• Economic impacts sea level rise can disrupt coastal industries (tourism, fisheries, ports), reduce property values, and strain public budgets
  • The cost of inaction may exceed the cost of adaptation in the long run
  • Distributional impacts some communities and sectors may bear a disproportionate share of the costs and benefits of adaptation
• Social and cultural impacts sea level rise can lead to the displacement of coastal communities, loss of cultural heritage sites, and changes in traditional livelihoods
  • Adaptation planning must consider the social and cultural dimensions of coastal change
  • Community engagement and participatory decision-making are essential for equitable and socially acceptable adaptation
• Environmental justice the disproportionate impacts of sea level rise on marginalized and vulnerable communities
  • Low-income and minority populations may have limited resources and capacity to adapt
  • Adaptation policies must address underlying social inequities and ensure fair distribution of costs and benefits
• Migration and displacement sea level rise may force people to relocate from coastal areas, either voluntarily or through planned retreat
  • Managed retreat can be a contentious and emotionally charged process
  • Receiving communities may face challenges in accommodating displaced populations

Future Challenges and Research Directions

• Deep uncertainty the difficulty in predicting long-term sea level rise due to uncertainties in greenhouse gas emissions, ice sheet dynamics, and climate system feedbacks
  • Robust decision-making and adaptive management approaches can help navigate deep uncertainty
  • Scenario planning can explore a range of possible futures and identify flexible adaptation pathways
• Compound risks the interaction of sea level rise with other coastal hazards (storms, precipitation, heat waves) and stressors (population growth, urbanization)
  • Understanding and managing compound risks requires interdisciplinary research and integrated risk assessments
• Tipping points and thresholds the potential for abrupt and irreversible changes in the climate system and coastal environments
  • Tipping points may be reached if certain thresholds (temperature, sea level) are exceeded
  • Research is needed to identify and anticipate tipping points and develop early warning systems
• Adaptation limits the point at which adaptation measures are no longer effective or feasible in reducing coastal risks
  • Physical limits (e.g., the maximum height of a seawall) and social limits (e.g., public acceptance of managed retreat) may constrain adaptation options
  • Transformative adaptation may be necessary in some cases, involving fundamental changes in coastal systems and societies
• Ecosystem-based adaptation the integration of biodiversity and ecosystem services into adaptation planning
  • Requires a better understanding of the role of coastal ecosystems in reducing vulnerability and enhancing resilience
  • Challenges include valuing ecosystem services, managing trade-offs, and ensuring long-term sustainability
• Governance and institutional challenges the need for effective coordination, collaboration, and decision-making across multiple scales and sectors
  • Adaptation planning must navigate complex jurisdictional boundaries, competing interests, and resource constraints
  • Adaptive governance approaches that are flexible, participatory, and learning-oriented can help build institutional capacity and resilience