Coastal Management and Sea Level Change

These flashcards cover key concepts related to coastal management and the impact of sea level change as discussed in the lecture.

What is the primary goal of coastal management?

The primary goal of coastal management is to implement strategies and measures designed to protect human lives, infrastructure (such as homes, businesses, and transport links), and valuable natural environments (like beaches, dunes, and ecosystems) from the damaging effects of coastal erosion, flooding, and sea-level rise. This involves balancing economic, social, and environmental considerations.

What percentage of the world's population lives within coastal areas?

Approximately 50% of the world's population lives within coastal zones or areas adjacent to coastlines. These regions are often densely populated due to economic opportunities (e.g., ports, tourism, fishing), fertile land, and access to natural resources, making them particularly vulnerable to coastal hazards.

What are the three main coastal management strategies?

The three main coastal management strategies are:

1. Hold the line: Involves building or maintaining artificial defenses to prevent the coastline from moving inland. This is typically done in areas with high economic value.
2. Advance the line: Extending the coastline seaward through land reclamation or new defenses, often to create new land for development or enhance existing protection.
3. Managed retreat: Allowing the coastline to erode back naturally, often relocating assets and population away from the immediate coastal edge, typically in areas where defense is deemed unsustainable or uneconomical. This strategy involves careful planning and often land-use adjustments.

What is hard engineering in coastal management?

Hard engineering refers to the construction of rigid, man-made structures, typically made of concrete, rock, or steel, to prevent erosion and flooding. Examples include sea walls (to absorb wave energy), groynes (to trap sediment), and breakwaters (to reduce wave force, often offshore). While effective in the short term, they can be expensive, visually intrusive, and may transfer erosion problems further along the coast.

What is soft engineering?

Soft engineering involves working with natural coastal processes to manage erosion and flooding, often by enhancing natural defenses or restoring coastal ecosystems. Techniques include beach nourishment (adding sand to widen beaches, providing a natural buffer), dune regeneration (planting vegetation to stabilize sand dunes, absorbing wave energy), and creating or restoring salt marshes (which dissipate wave energy and trap sediment). These methods are generally more environmentally friendly, sustainable, and less intrusive than hard engineering.

Define eustatic change in relation to sea level.

Eustatic sea-level change refers to a global alteration in the absolute volume of water in the oceans, or a change in the capacity of the ocean basins. This is primarily caused by factors such as:

• Thermal expansion of ocean water: As ocean water warms due to climate change, it expands in volume.
• Melting of glaciers and ice sheets: The addition of meltwater from land-based ice (e.g., Greenland and Antarctic ice sheets, mountain glaciers) directly increases the total volume of water in the oceans.
• Large-scale changes in the shape and volume of ocean basins: This is a much slower process due to tectonic activity affecting the seafloor.

What is isostatic change?

Isostatic sea-level change describes localized shifts in land elevation relative to sea level, caused by the vertical movement of the Earth's crust. This commonly occurs due to:

• Post-glacial rebound: The slow rise of land masses that were previously depressed by the immense weight of massive ice sheets during glacial periods (e.g., Scandinavia, parts of North America). As the ice melts, the land 'rebounds' upwards.
• Sediment loading: The sinking (subsidence) of land areas due to the accumulation of heavy sediment deposits, often in large river deltas.
• Tectonic uplift or subsidence: Localized crustal movements due to earthquakes or deeper plate tectonic processes.

What are submergent coastlines?

Submergent coastlines are coastal landscapes formed when the sea level rises relative to the land, inundating geological features that were once dry. This can result from eustatic sea-level rise (global rise in water volume) or isostatic subsidence (local sinking of land). Characteristic features of submergent coastlines include rias (submerged river valleys) and fjords (submerged glacial valleys), which are typically deep and narrow, showcasing evidence of a drowned landscape.

What are Rias?

Rias are distinctive coastal features that are essentially submerged river valleys. They are formed when rising sea levels (often due to deglaciation and eustatic rise) flood existing river valleys. The original topography of the river valley is preserved, resulting in a funnel-shaped, often winding inlet that gradually deepens and widens towards the sea, with hills forming interfluves (ridges between valleys) along the sides. They often have dendritic (tree-like) patterns.

How does climate change impact coastal areas?

Climate change significantly impacts coastal areas primarily through two mechanisms:

1. Sea-level rise: Global temperature increases lead to the thermal expansion of ocean water and the accelerated melting of glaciers and ice sheets, contributing to higher sea levels. This results in increased coastal flooding, permanent inundation of low-lying areas, enhanced wave erosion, and salinization of groundwater.
2. Increased storm intensity and frequency: Warmer ocean temperatures can fuel more powerful tropical storms and cyclones, leading to greater storm surges, higher wave energy, and more severe coastal damage to infrastructure and natural ecosystems.

What are the predicted sea level rises according to the IPCC by 2100?

The Intergovernmental Panel on Climate Change (IPCC) estimates that global mean sea level is projected to rise by 0.3 to 1 meter by 2100, depending on various greenhouse gas emission scenarios and the extent of future warming. Higher emissions scenarios lead to predictions closer to or exceeding the 1-meter mark, posing significant threats to coastal communities, ecosystems, and infrastructure worldwide, requiring extensive adaptation measures.

Which coastal management strategy is considered more sustainable?

Soft engineering approaches are widely considered more sustainable than hard engineering because they work with natural processes, minimize ecological disruption, and often enhance natural habitats. They typically involve lower long-term maintenance costs and are more adaptable to future changes like accelerated sea-level rise, offering environmentally sound and often more cost-effective solutions in the long run. They aim for long-term resilience rather than short-term defense.

What are potential negative impacts of hard engineering?

While effective in protecting specific areas, hard engineering structures have several negative impacts:

• High cost: Construction and ongoing maintenance are typically very expensive, straining public budgets.
• Aesthetic impact: Structures like sea walls and rock armor can be visually unappealing, disrupting natural landscapes and tourism appeal.
• Environmental damage: They can destroy natural habitats (e.g., beaches, dunes, salt marshes) during construction and operation by altering natural processes.
• "Terminal groyne syndrome" or downdrift erosion: They often interfere with natural sediment transport (longshore drift), leading to erosion of beaches downdrift (further along the coast) from the defended area, effectively shifting the problem elsewhere.
• Safety risks: Structures can pose dangers to public access and recreation.

Why is coastal management important?

Coastal management is crucial because coastlines are dynamic environments facing increasing threats from natural processes amplified by climate change. It is important for:

• Protecting lives and property: Safeguarding the large populations and valuable infrastructure (e.g., homes, industries, transport links) located in coastal areas from erosion and flooding.
• Preserving ecosystems: Conserving vital coastal habitats (e.g., coral reefs, mangroves, salt marshes, dunes) that provide biodiversity, natural storm defense, and ecosystem services.
• Maintaining economic activities: Protecting industries such as tourism, fishing, shipping, and agriculture that rely on healthy and stable coastlines.
• Reducing disaster risk: Mitigating the significant social, environmental, and economic costs associated with coastal erosion, storm surges, and flooding, thereby enhancing community resilience.

What is the purpose of a cost-benefit analysis (CBA) in coastal management?

A Cost-Benefit Analysis (CBA) in coastal management is a systematic process used to evaluate the economic viability and effectiveness of different defense strategies. Its purpose is to:

• Identify priority areas: Determine which stretches of coastline provide the greatest economic and social benefit from protection versus the cost of implementing and maintaining defenses.
• Quantify values: Assess the monetary value of assets at risk (e.g., property, agricultural land, infrastructure, tourist revenue) and the potential economic damages avoided by intervention. It also tries to quantify environmental benefits or costs.
• Compare options: Help decision-makers choose the most economically efficient and socially beneficial management approach by comparing the costs of construction, maintenance, and environmental impact against the benefits of protection or relocation. This aids in strategic planning and resource allocation.

What can increased storminess lead to?

Increased storminess, often a consequence of climate change creating more intense and frequent extreme weather events, can lead to severe and progressive coastal degradation. Specifically, it causes:

• Accelerated erosion: Powerful waves and storm surges generated by storms strip away sediment from beaches and dunes at a much faster rate than normal, leading to significant land loss.
• Reduced recovery time: With more frequent and intense storms, natural processes like sediment accretion (the building up of beaches) do not have sufficient time to rebuild eroded features before the next event. This results in long-term, irreversible damage to natural coastal defenses and landforms, making coastlines more vulnerable.

What are the effects of climate change on glacial regions?

Climate change, characterized by rising global temperatures, has profound effects on glacial regions worldwide. Warmer temperatures accelerate the melting of:

• Mountain glaciers: These shrink and disappear rapidly, contributing directly to sea-level rise and significantly impacting freshwater supplies downstream for drinking water, irrigation, and hydropower.
• Ice sheets (e.g., Greenland, Antarctica): Large-scale melting and calving events from these massive ice bodies contribute substantially to eustatic sea-level rise. The loss of ice also reduces the Earth's albedo (reflectivity) in those regions, potentially leading to further warming as more solar radiation is absorbed by the darker land or ocean surface.

What is the predicted annual increase in global sea levels due to climate change?

The annual increase in global mean sea levels due to climate change is not a fixed rate but is accelerating. While the average rate was around $1.7 \text{ mm/year}$ over the 20th century, it has increased to approximately $3.6 \text{ mm/year}$ (from 2006–2018) and is projected to accelerate further throughout the 21st century. Future annual rates could potentially reach several millimeters per year depending on emission pathways and the response of ice sheets, impacting the overall cumulative rise by 2100.