🌊Coastal Resilience Engineering Unit 6 – Coastal Infrastructure Engineering

Key Concepts and Definitions

• Coastal infrastructure encompasses structures, facilities, and systems built along coastlines to support human activities, protect against coastal hazards, and enhance resilience
• Coastal resilience the ability of coastal systems to withstand, adapt to, and recover from disturbances while maintaining essential functions and services
• Coastal processes include waves, tides, currents, sediment transport, and erosion that shape and influence the coastal environment
• Coastal dynamics the complex interactions between physical, biological, and chemical processes in coastal systems that drive changes over time
• Coastal hazards natural phenomena (storm surges, hurricanes, tsunamis) that pose risks to coastal communities and infrastructure
• Coastal vulnerability the susceptibility of coastal areas to damage or loss due to exposure to hazards and lack of adaptive capacity
• Coastal management the integrated approach to planning, protecting, and enhancing coastal resources while balancing social, economic, and environmental needs
• Coastal adaptation strategies and measures implemented to reduce vulnerability and increase resilience to changing coastal conditions (sea-level rise, climate change)

Coastal Processes and Dynamics

• Waves generated by wind blowing over the ocean surface, characterized by height, period, and direction
  • Wave height influenced by wind speed, duration, and fetch (distance over which wind blows)
  • Wave period the time interval between successive wave crests, affecting wave energy and sediment transport
• Tides the rise and fall of sea levels caused by gravitational forces of the moon and sun
  • Tidal range the vertical difference between high and low tides, varying by location and influenced by coastal geometry
• Currents the horizontal movement of water driven by various forces (winds, tides, density differences)
  • Longshore currents parallel to the shoreline, generated by waves approaching at an angle and contributing to sediment transport
• Sediment transport the movement of sand, gravel, and other particles by waves, currents, and wind
  • Cross-shore transport the onshore and offshore movement of sediment, affecting beach profiles and shoreline position
  • Longshore transport the movement of sediment along the coast, influenced by wave angle and longshore currents
• Coastal erosion the wearing away of land and removal of beach or dune sediments by waves, currents, tides, or wind
  • Erosion rates vary depending on factors such as wave energy, sediment supply, and coastal geology
• Sea-level rise the long-term increase in mean sea level due to factors such as thermal expansion of oceans and melting of glaciers and ice sheets
  • Accelerated sea-level rise exacerbates coastal erosion, flooding, and saltwater intrusion, necessitating adaptation measures

Types of Coastal Infrastructure

• Seawalls vertical or sloping structures built parallel to the shoreline to protect against erosion and wave action
  • Seawalls can be constructed using materials such as concrete, stone, or steel sheet piles
• Revetments sloping structures placed on banks or cliffs to absorb wave energy and prevent erosion
  • Revetments typically consist of layers of rock, concrete blocks, or other durable materials
• Breakwaters offshore structures designed to dissipate wave energy and reduce wave heights in sheltered areas
  • Breakwaters can be detached (parallel to shore) or shore-connected (perpendicular to shore)
• Groins narrow, shore-perpendicular structures built to trap and retain sediment, stabilizing beaches
  • Groins interrupt longshore sediment transport, causing accretion on the updrift side and erosion on the downdrift side
• Jetties structures extended perpendicular from the shore at inlets or river mouths to stabilize navigation channels
  • Jetties prevent channel infilling by trapping sediment and directing currents
• Beach nourishment the artificial placement of sand on beaches to widen and elevate the shoreline, enhancing protection and recreational value
  • Nourishment requires ongoing maintenance and monitoring to ensure long-term effectiveness
• Dune restoration the rebuilding or stabilization of coastal dunes using vegetation, fencing, or sand placement
  • Dunes serve as natural barriers against storm surges and provide habitat for coastal species
• Living shorelines nature-based approaches that use a combination of plants, oyster reefs, and structural elements to stabilize shorelines and enhance ecological functions

Design Principles for Coastal Structures

• Functionality coastal structures should be designed to effectively serve their intended purpose (protection, navigation, recreation) under site-specific conditions
• Structural stability structures must withstand forces exerted by waves, currents, and storm surges without failure or significant damage
  • Stability is achieved through proper material selection, dimensioning, and foundation design
• Hydraulic performance the ability of structures to interact with and modify coastal processes as intended
  • Hydraulic performance considerations include wave transmission, reflection, overtopping, and sediment transport effects
• Adaptability designing structures that can be modified or adjusted in response to changing environmental conditions or user needs
  • Adaptable designs may incorporate modular components, adjustable crest heights, or provisions for future upgrades
• Constructability the ease and feasibility of building and maintaining coastal structures given site constraints, available resources, and construction methods
  • Constructability factors include access, staging areas, equipment requirements, and weather windows
• Durability selecting materials and construction techniques that ensure long-term performance and resistance to deterioration
  • Durability considerations include corrosion resistance, abrasion resistance, and compatibility with the marine environment
• Aesthetics and public acceptance designing structures that blend with the natural surroundings and enhance visual appeal
  • Aesthetic considerations may involve the use of natural materials, landscaping, or architectural features
• Cost-effectiveness balancing initial construction costs with long-term maintenance, repair, and replacement costs to achieve optimal life-cycle performance
  • Cost-effectiveness analysis should consider both direct and indirect costs, as well as potential economic benefits

Construction Materials and Techniques

• Concrete widely used in coastal structures due to its strength, durability, and versatility
  • Reinforced concrete incorporates steel bars or mesh to improve tensile strength and crack resistance
  • Precast concrete elements (blocks, armor units) can be manufactured offsite and assembled on location
• Steel used in sheet pile walls, tubular piles, and structural frameworks for its high strength-to-weight ratio
  • Corrosion protection (coatings, cathodic protection) is essential for steel in marine environments
• Rock and riprap natural or quarried stone used in revetments, breakwaters, and toe protection
  • Rock size and gradation are selected based on wave conditions and structure design
• Geotextiles permeable fabrics used for filtration, separation, and reinforcement in coastal structures
  • Geotextiles prevent soil loss, reduce settlement, and enhance stability
• Timber historically used in coastal structures but less common today due to durability limitations
  • Treated timber can be used for walkways, fender systems, and temporary structures
• Innovative materials fiber-reinforced polymers (FRP), geosynthetic containers, and eco-friendly alternatives (oyster shells, bio-based polymers) are being explored for coastal applications
• Construction techniques for coastal structures include:
  • Land-based methods using cranes, excavators, and trucks for onshore or near-shore projects
  • Water-based methods using barges, floating cranes, and specialized vessels for offshore construction
  • Underwater techniques using divers, remotely operated vehicles (ROVs), and underwater tools for installation and inspection

Environmental Impact and Sustainability

• Habitat alteration coastal structures can modify or destroy natural habitats (beaches, dunes, wetlands) essential for marine and terrestrial species
  • Habitat fragmentation and loss can disrupt ecological processes and biodiversity
• Water quality impacts construction activities and materials may release pollutants, sediments, or nutrients into coastal waters
  • Turbidity, sedimentation, and contamination can affect aquatic organisms and ecosystem health
• Hydrodynamic changes structures can alter wave patterns, currents, and sediment transport, leading to unintended erosion or accretion
  • Modified hydrodynamics may affect shoreline stability, navigation, and recreational activities
• Ecological connectivity disruption structures can create barriers to the movement of organisms, nutrients, and energy between coastal and marine ecosystems
  • Disrupted connectivity can impact species migration, reproduction, and population dynamics
• Invasive species introduction construction materials and equipment can introduce non-native species into coastal environments
  • Invasive species may outcompete native species and alter ecosystem balance
• Carbon footprint the greenhouse gas emissions associated with the production, transportation, and installation of construction materials
  • Sustainable practices (local sourcing, recycled materials, low-carbon alternatives) can reduce the carbon footprint of coastal projects
• Life-cycle assessment (LCA) a holistic approach to evaluating the environmental impacts of coastal structures throughout their entire life cycle
  • LCA considers resource extraction, manufacturing, construction, operation, maintenance, and decommissioning phases
• Ecosystem-based management (EBM) an integrated approach that considers the interdependence of ecological, social, and economic systems in coastal decision-making
  • EBM aims to balance human activities with the conservation and sustainable use of coastal resources

Resilience Strategies and Adaptation

• Risk assessment identifying and evaluating the potential impacts of coastal hazards on infrastructure, communities, and ecosystems
  • Risk assessment considers the likelihood and consequences of hazard events, as well as vulnerability and exposure factors
• Vulnerability reduction measures aimed at decreasing the susceptibility of coastal systems to damage or disruption
  • Vulnerability reduction strategies include structural upgrades, land-use planning, and social programs
• Adaptive capacity building enhancing the ability of coastal communities and institutions to anticipate, cope with, and recover from coastal hazards
  • Adaptive capacity building involves education, training, and resource mobilization
• Nature-based solutions (NbS) the use of natural systems and processes to address coastal challenges and provide co-benefits
  • NbS examples include wetland restoration, living shorelines, and green infrastructure
• Managed retreat the strategic relocation of people, assets, and activities away from high-risk coastal areas
  • Managed retreat can involve land acquisition, zoning changes, and incentives for voluntary relocation
• Adaptive management a flexible and iterative approach to coastal management that allows for adjustments based on monitoring, learning, and changing conditions
  • Adaptive management involves setting objectives, implementing actions, monitoring outcomes, and revising strategies as needed
• Community engagement involving local stakeholders in the planning, design, and implementation of coastal resilience projects
  • Community engagement ensures that local knowledge, needs, and priorities are incorporated into decision-making
• Resilience financing mechanisms funding sources and instruments to support the implementation of coastal resilience measures
  • Financing mechanisms include public-private partnerships, insurance schemes, and resilience bonds

Case Studies and Real-World Applications

• The Netherlands Delta Works a series of dams, sluices, locks, dikes, and storm surge barriers designed to protect the low-lying Netherlands from flooding
  • The Maeslant Barrier a movable storm surge barrier that closes off the New Waterway near Rotterdam during high water events
• The Maldives Hulhumalé Island an artificial island created to relieve population pressure and adapt to sea-level rise
  • The island features elevated buildings, wide beaches, and a protective seawall
• United States Gulf Coast restoration efforts following Hurricane Katrina in 2005
  • The Louisiana Coastal Master Plan a comprehensive strategy for coastal protection, restoration, and adaptation
  • The Living Shoreline Demonstration Project in Alabama using oyster reefs and marsh plantings to stabilize eroding shorelines
• Australia Gold Coast Seawall a 30-kilometer seawall and beach nourishment project to protect the tourist destination from erosion and storm damage
  • The project incorporates a sand bypassing system to maintain beach widths and surf quality
• Japan Okinotorishima Island the southernmost point of Japan, threatened by sea-level rise and erosion
  • The island is being protected by steel and concrete structures, as well as coral transplantation to promote natural reef growth
• Bangladesh Coastal Embankment Improvement Project upgrading and rehabilitating embankments to protect coastal communities from tidal flooding and storm surges
  • The project includes the construction of cyclone shelters and the improvement of drainage systems
• Belize Coral Reef Restoration using coral nurseries and transplantation techniques to restore degraded reef habitats
  • The project aims to enhance coastal protection, biodiversity, and tourism benefits provided by healthy coral reefs
• Miami Beach, Florida Stormwater Management upgrading drainage systems and installing pumps to alleviate flooding during high tides and heavy rainfall events
  • The project is part of the city's comprehensive strategy to adapt to sea-level rise and improve resilience