Build at least 2 seawalls on the island in order to continue protecting the island’s natural environment for socio-economic benefits. 

Strategy 

Building coastal seawalls on islands in 2025 involves a shift from traditional “hard engineering” to hybrid and nature-based strategies designed for long-term resilience against sea-level rise.  

1. Hybrid and Nature-Based Solutions (NbS) 

Modern strategies increasingly combine man-made structures with natural elements to absorb wave energy rather than just reflecting it.  

• Geobags: Using large, sand-filled geobags for a more economical, though less permanent can last long up to 50 years. 

2. Traditional Hard Engineering 

Conventional methods are still used for high-risk infrastructure where immediate protection is critical.  

• Gabions: Wire mesh baskets filled with locally sourced stone are a cost-effective way to stabilize banks and can support vegetation growth over time.  

3. Integrated Coastal Management  

Successful seawall construction requires a holistic planning approach to avoid “maladaptation,” where a wall protects one area but worsens erosion elsewhere.  

• Site Assessment: Detailed mapping of tidal ranges, wave heights, and hydrodynamic forces is essential before design. 

• Community-Led Construction: Projects in the Solomon Islands and Fiji prioritize community training and participatory mapping to ensure local maintenance and buy-in. 

• Backfilling and Drainage: Seawalls must include weep holes or filters to relieve water pressure from behind the wall and are often backfilled with sand or soil to stabilize the structure.  

Outcomes 

Building seawalls results in a complex set of outcomes that range from immediate physical protection to long-term environmental and social impacts.  

Primary Protective Outcomes 

• Erosion and Flood Défense: Seawalls serve as a hard barrier that reflects or absorbs wave energy, protecting coastal properties and infrastructure from upland erosion and surge flooding. 

• Property Stabilization: By preventing the land from being washed away, seawalls maintain the structural stability of homes and businesses and can increase property values by securing a permanent shoreline. 

• Public Safety: They provide a stable barrier that reduces the risk of injury from waves and surges for residents and visitors along developed shorelines. 

• Storm Resilience: Protect entire villages from tidal surges and extreme weather events.  

Environmental and Physical Impacts 

• Scrub and Passive Erosion: Vertical seawalls often reflect wave energy downward, which can cause “scour” at the base of the wall, eventually undermining its stability. 

• Sediment Starvation: By blocking the natural exchange of sand between land and sea, seawalls often cause adjacent beaches to narrow or disappear because they no longer receive replenishment from eroding bluffs. 

• Habitat Loss: Hardening the shoreline can destroy intertidal habitats like wetlands and intertidal beaches, disrupting the organisms that rely on these “soft” transitions. 

Economic and Social Outcomes 

• High Costs: Seawalls are expensive to design, construct, and maintain and regular maintenance is required to prevent crumbling. 

• Stopgap Utility: In island nations seawalls provide vital time for communities to adapt or consider relocation in the face of rising sea levels.