Strategies for Mitigating the Impacts of Sea Level Rise

Rising seas are reshaping coastlines around the world. By 2100, approximately one billion people could be impacted by sea level rise, threatening homes, infrastructure, and entire communities. As coastal areas face increased flooding, erosion, and storm surge, governments and communities must choose how to respond. The path forward isn’t simple, but three main strategies have emerged to help communities adapt: planned retreat, adaptive measures, and defensive structures.

Understanding the challenge ahead 🔗

Sea level rise isn’t just about water slowly creeping up the shore. It brings multiple threats that compound over time. Coastal erosion accelerates, storm damage intensifies, and saltwater intrusion contaminates freshwater supplies. The urgency is real-extreme flooding events that once occurred rarely will become annual occurrences by 2100 in many coastal areas.

Response strategies generally fall into three categories: protect, accommodate, and retreat. Each approach has distinct costs, benefits, and trade-offs. The most effective solutions often combine multiple strategies, adapting over time as conditions change.

Planned retreat: Moving to higher ground 🔗

Planned retreat, also called managed retreat, involves the coordinated relocation of people, buildings, and infrastructure away from high-risk coastal areas. Unlike emergency evacuations, this is a proactive, organized approach that gives communities time to plan where and how to move.

How planned retreat works 🔗

At its core, planned retreat means permanently moving development out of harm’s way. This can happen through voluntary buyout programs where governments purchase at-risk properties, or through land-use policies that restrict new construction in vulnerable zones. Communities implement this strategy through updated zoning maps, building codes, and strategic planning that accounts for future sea level projections.

The timing of retreat varies. Some communities opt for immediate, all-at-once relocation of entire neighborhoods. Others use trigger-based approaches, where retreat occurs when specific thresholds are reached-such as when erosion brings the shoreline within a certain distance of structures. Research from Hawaii shows that threshold-based retreat can balance costs with public safety while preserving more beach area over time.

Benefits and challenges 🔗

Planned retreat offers the most permanent solution to coastal hazards. Once communities move to higher ground, they’re no longer at risk from rising seas. This approach also creates opportunities to restore natural coastal ecosystems like wetlands and dunes, which provide additional storm protection for remaining development.

However, retreat faces significant obstacles. The financial costs are substantial-property acquisition alone can run into hundreds of millions of dollars for a single neighborhood. Beyond money, studies document negative impacts on well-being and anxiety among relocated residents. Cultural attachments to place, loss of community identity, and equity concerns about who gets assistance all complicate retreat efforts.

Adaptive measures: Building resilience in place 🔗

Adaptive measures modify existing development or design new construction to reduce vulnerability without abandoning coastal areas. These strategies, also called accommodation approaches, allow communities to remain in place while managing increased risks.

Elevating structures and infrastructure 🔗

One of the most common adaptive measures is elevating buildings above projected flood levels. This can involve raising entire structures on stilts, building on raised foundations, or using fill to elevate building sites. Critical equipment like HVAC systems, electrical panels, and generators get moved to upper floors or waterproof enclosures.

Elevating buildings above base flood elevation can significantly reduce flood insurance premiums-sometimes by over 70 percent. In some cases, floating or amphibious structures that can rise with floodwaters provide flexible solutions for areas expecting long-term inundation.

Improving drainage and water management 🔗

As sea levels rise, existing drainage systems become less effective. Water can’t flow downhill if the ocean is higher than the outfall pipes. Communities respond by upgrading drainage infrastructure with larger capacity systems, installing pump stations to move water against gravity, and creating retention basins to temporarily store excess stormwater.

These modifications also address another threat: saltwater intrusion into groundwater. Modified drainage helps manage groundwater levels and can include measures to prevent seawater from backing up through underground pipes and contaminating freshwater sources.

Flexible coastal management policies 🔗

Adaptive measures extend beyond physical structures to include policy and planning tools. Building codes can require sea level rise considerations in all new coastal construction, mandating minimum elevation standards and setback distances from the shoreline. Zoning ordinances might restrict development types in vulnerable areas or require easily removable structures that can be relocated when threatened.

Insurance schemes, early warning systems, and comprehensive hazard mapping all support adaptive management by improving risk awareness and enabling better decision-making.

Defensive structures: Holding back the water 🔗

Defensive approaches use engineered structures to maintain current shorelines and protect existing development. These “hard” protection measures include seawalls, levees, bulkheads, and revetments designed to block or redirect water.

Types of coastal defenses 🔗

Seawalls are vertical or sloped barriers built at the shoreline to protect against wave action and flooding. They work by reflecting wave energy back to sea, but can accelerate erosion of adjacent unprotected beaches.

Levees are earthen embankments, often along rivers or in low-lying coastal areas, that create barriers against flooding. When built from concrete or other hard materials, they function similarly to floodwalls.

Other structures include breakwaters (offshore barriers that reduce wave energy), revetments (sloped armoring on shoreline faces), and bulkheads (vertical walls that prevent erosion).

Benefits and limitations 🔗

Defensive structures provide immediate, visible protection for valuable coastal property and infrastructure. They can be essential for protecting critical facilities like ports, power plants, and wastewater treatment facilities that cannot easily relocate. In the United States alone, $300 billion in shoreline armoring costs are forecast by 2100.

However, these structures come with significant drawbacks. Recent research shows that seawalls in one location can increase flooding in other areas-sometimes even 60 miles away in interconnected bays and estuaries. This happens because hard structures alter natural water flow patterns and can amplify tides by reducing friction in shallow coastal areas.

The environmental costs are substantial too. Seawalls disrupt sediment movement, accelerate beach loss, and reduce space for coastal ecosystems. They also create a false sense of security-structures designed for current conditions may be overwhelmed as sea levels continue rising, leading to catastrophic failures.

Natural and hybrid solutions 🔗

Increasingly, communities are turning to “soft” defenses that work with natural processes. Living shorelines use native vegetation, oyster reefs, and restored wetlands to dissipate wave energy while maintaining ecosystem function. Beach nourishment programs add sand to eroding beaches, though this requires ongoing maintenance. These nature-based approaches often cost less over time and provide co-benefits like improved water quality and wildlife habitat.

Choosing the right approach 🔗

No single strategy works for every community. The California Coastal Commission emphasizes that appropriate adaptation strategies differ by location based on local hazards, resources, and legal context. Many communities will need to use multiple approaches simultaneously and adjust their strategies as conditions evolve.

The decision often comes down to cost, timeframe, and local values. Planned retreat offers long-term safety but requires overcoming significant social and economic barriers. Adaptive measures buy time and allow continued coastal living but may ultimately prove insufficient. Defensive structures provide immediate protection but can create new problems and require ongoing maintenance investments.

Successful adaptation requires early action, community engagement, and recognition that today’s decisions will shape coastal communities for generations to come. The communities that start planning now-before crisis forces hasty choices-will be best positioned to manage the impacts of rising seas.

What do you think? Should coastal communities prioritize protecting current development or begin planning for retreat? How can we ensure adaptation strategies are equitable and don’t disproportionately burden vulnerable populations?

References

1. https://www.nature.com/articles/s41598-023-38939-4
2. https://www.coastal.ca.gov/climate/slr/vulnerability-adaptation/adaptation/
3. https://oceandecade.org/publications/special-report-managed-retreat-preparing-coastal-cities-for-sea-level-rise/
4. https://rma.venturacounty.gov/divisions/planning/sea-level-rise-adaptation-options/
5. https://www.nature.com/articles/s41598-024-53277-9
6. https://earth.gov/sealevel/us/sea-level-101/what-can-we-do/
7. https://challenge.abettercity.org/toolkits/climate-resilience-toolkits/flooding-and-sea-level-rise/building-elevation-and-floating
8. https://eri.iu.edu/erit/strategies/sea-level-rise.html
9. https://sp.copernicus.org/articles/3-slre1/6/2024/
10. https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2021.740602/full
11. https://www.permacastwalls.com/the-difference-between-floodwalls-levees-and-sea-walls
12. https://pmc.ncbi.nlm.nih.gov/articles/PMC8307291/
13. https://www.scientificamerican.com/article/walling-off-one-coastal-area-can-flood-another/
14. https://www.climatechangenews.com/2022/03/03/scientists-warn-seawalls-can-make-rising-waters-worse-in-the-long-run/
15. https://toolkit.climate.gov/coastal-erosion