🌊Coastal Resilience Engineering Unit 7 – Shoreline Management Techniques

Key Concepts in Shoreline Management

• Shoreline management involves protecting and preserving coastal areas from erosion, flooding, and other hazards
• Aims to balance the needs of coastal communities, infrastructure, and ecosystems
• Considers factors such as sea level rise, storm surges, and human activities (beach nourishment, coastal development)
• Employs a combination of hard engineering structures (seawalls, groins) and soft engineering approaches (dune restoration, living shorelines)
• Requires understanding of coastal processes, sediment transport, and wave dynamics
• Involves stakeholder engagement and public participation in decision-making processes
• Incorporates principles of sustainability, resilience, and adaptive management
• Relies on data collection, monitoring, and modeling to assess the effectiveness of management strategies

Coastal Processes and Erosion Mechanisms

• Coastal processes shape the shoreline through the interaction of waves, tides, currents, and sediment transport
• Wave action is a primary driver of coastal erosion, causing the removal and redistribution of sediment
• Longshore currents transport sediment parallel to the shoreline, resulting in the formation of beaches, spits, and barrier islands
• Cross-shore transport moves sediment perpendicular to the shoreline, leading to the formation of offshore bars and beach profiles
• Tidal currents influence sediment transport and can contribute to erosion or accretion depending on their strength and direction
• Sea level rise exacerbates coastal erosion by increasing the frequency and severity of flooding and storm surges
• Human activities (dredging, coastal development) can disrupt natural sediment supply and accelerate erosion rates
• Coastal erosion can lead to the loss of beaches, dunes, and wetlands, as well as damage to infrastructure and property

Types of Shoreline Protection Structures

• Seawalls are vertical or near-vertical structures designed to protect the shoreline from wave action and erosion
  • Constructed using materials such as concrete, steel, or stone
  • Can be effective in protecting critical infrastructure but may accelerate erosion in adjacent areas
• Revetments are sloping structures placed along the shoreline to absorb wave energy and prevent erosion
  • Typically made of rock, concrete, or other durable materials
  • Can be designed to blend in with the natural environment and provide habitat for marine organisms
• Groins are perpendicular structures that extend from the shore into the water to trap sediment and stabilize beaches
  • Can be effective in maintaining beach width but may cause downdrift erosion
  • Require careful design and placement to minimize adverse impacts on adjacent shorelines
• Breakwaters are offshore structures that dissipate wave energy before it reaches the shore
  • Can be fixed or floating and constructed using various materials (rock, concrete, steel)
  • Provide calm water conditions for boating and recreation but may alter sediment transport patterns
• Sills are low-profile structures placed parallel to the shore to reduce wave energy and promote sediment deposition
  • Often used in conjunction with living shorelines to create a stable substrate for vegetation growth
• Jetties are structures built at the entrance of harbors or river mouths to stabilize navigation channels and prevent sediment accumulation
  • Can interrupt longshore sediment transport and cause erosion or accretion in adjacent areas

Soft Engineering Approaches

• Beach nourishment involves the placement of sand on eroded beaches to restore their width and elevation
  • Can provide temporary protection against erosion and enhance recreational opportunities
  • Requires regular maintenance and may have ecological impacts on beach habitats
• Dune restoration aims to rebuild and stabilize sand dunes using native vegetation and sand fencing
  • Dunes serve as natural barriers against storm surges and provide habitat for coastal species
  • Requires community involvement and public education to minimize human disturbance
• Living shorelines use a combination of natural materials (oyster reefs, marsh plants) and structural elements to stabilize the shoreline
  • Provide ecological benefits by creating habitat for fish, birds, and other wildlife
  • Can adapt to changing environmental conditions and enhance coastal resilience
• Managed retreat involves the relocation of coastal infrastructure and communities away from high-risk areas
  • Allows for the natural migration of shorelines and the preservation of coastal ecosystems
  • Requires long-term planning, public acceptance, and financial incentives
• Coastal wetland restoration aims to restore the ecological functions of degraded or lost wetlands
  • Wetlands act as natural buffers against storm surges and provide valuable habitat for marine and terrestrial species
  • Requires hydrologic restoration, sediment management, and invasive species control

Hard Engineering Solutions

• Seawalls provide a hard barrier between the land and the sea, protecting against wave action and erosion
  • Can be designed to withstand extreme storm events and sea level rise
  • May cause increased erosion in adjacent areas and disrupt natural beach processes
• Revetments absorb wave energy and stabilize the shoreline, reducing erosion rates
  • Can be constructed using various materials (rock, concrete, geotextiles) depending on site conditions
  • May alter beach profiles and reduce sediment supply to downdrift areas
• Groins trap sediment on the updrift side, maintaining beach width and reducing erosion
  • Require careful spacing and orientation to minimize adverse impacts on adjacent shorelines
  • May cause downdrift erosion and disrupt longshore sediment transport
• Breakwaters dissipate wave energy before it reaches the shore, creating calm water conditions
  • Can be designed as submerged or emergent structures, depending on the desired level of protection
  • May alter sediment transport patterns and cause accretion or erosion in adjacent areas
• Sills reduce wave energy and promote sediment deposition, creating a stable substrate for vegetation growth
  • Often used in combination with living shorelines to enhance ecological benefits
  • Require proper design and placement to avoid adverse impacts on water circulation and habitat connectivity

Environmental Impact Assessment

• Environmental Impact Assessment (EIA) is a process that evaluates the potential environmental consequences of shoreline management projects
• Identifies and assesses the direct, indirect, and cumulative impacts of proposed activities on coastal ecosystems and resources
• Considers factors such as water quality, sediment transport, habitat loss, and biodiversity
• Involves stakeholder consultation and public participation to incorporate diverse perspectives and concerns
• Requires the development of mitigation measures to minimize adverse impacts and enhance environmental benefits
• Includes monitoring and adaptive management strategies to assess the effectiveness of management actions over time
• Ensures compliance with environmental regulations and policies at local, state, and federal levels
• Provides a basis for informed decision-making and the selection of environmentally sustainable management options

Cost-Benefit Analysis of Management Techniques

• Cost-Benefit Analysis (CBA) is a tool used to evaluate the economic feasibility and efficiency of shoreline management techniques
• Compares the costs of implementing a management strategy with the expected benefits over a specified time horizon
• Considers direct costs (construction, maintenance, materials) and indirect costs (environmental impacts, social disruption)
• Evaluates benefits in terms of avoided damages, increased property values, enhanced recreational opportunities, and ecosystem services
• Uses discounting techniques to account for the time value of money and express costs and benefits in present value terms
• Incorporates uncertainty and risk analysis to assess the sensitivity of results to changes in key parameters and assumptions
• Provides a framework for comparing the relative merits of different management options and selecting the most cost-effective solution
• Requires the monetization of non-market values (ecological benefits, cultural heritage) to ensure a comprehensive assessment

Case Studies and Real-World Applications

• The Netherlands' Delta Works is an example of a large-scale hard engineering project that protects against coastal flooding
  • Consists of a series of dams, sluices, and storm surge barriers that regulate water levels and prevent inundation
  • Demonstrates the effectiveness of hard engineering solutions in mitigating flood risks but also highlights the high costs and environmental impacts
• The Chesapeake Bay Living Shorelines Initiative promotes the use of soft engineering approaches to stabilize eroding shorelines
  • Involves the construction of oyster reefs, marsh plantings, and sand containment structures to create a natural buffer against wave action
  • Showcases the ecological benefits of living shorelines in terms of habitat creation, water quality improvement, and enhanced biodiversity
• The managed retreat of the village of Newtok, Alaska, illustrates the challenges and opportunities of relocating coastal communities in response to climate change
  • The village is being threatened by coastal erosion, permafrost thaw, and sea level rise, necessitating a planned relocation to a safer site
  • Highlights the importance of community engagement, cultural preservation, and long-term planning in the face of environmental hazards
• The beach nourishment project in Miami Beach, Florida, demonstrates the use of soft engineering techniques to combat erosion and maintain beach width
  • Involves the periodic placement of sand dredged from offshore sources to restore eroded beaches and protect coastal infrastructure
  • Illustrates the ongoing maintenance requirements and potential ecological impacts of beach nourishment as a shoreline management strategy