Nature-based Solutions
Coral Reef Systems and Seagrasses as Coastal Defense
Climate Adaptation Effectiveness
In order to determine the effectivity of Eco-DRR, wave model simulations were conducted on a coastal environment with an extensive reef system. In one scenario, monsoonal winds and storm conditions were simulated. As sea level rise is projected to continue in the incoming years, a scenario was also simulated to determine how the reef systems help in preventing disasters. In both simulations, it was observed that the reef systems significantly dissipated the wave energy which lessened the amount of water coming onto the coast [6]. Aside from coral reefs, seagrasses and mangroves also had similar effects to the wave energy [1][2].
Climate Hazards
- Sea Level Rise
- Tropical Cyclone
Locations
- Barangay Bagacay and Barangay Rizal Municipality of Sorsogon, Sorsogon, Region V (Bicol Region)
Adaptation Sectors
- Biodiversity
- Coastal Areas
- Disaster Risk Reduction
- Ecosystem-Based Approaches
- Marine and Fisheries
CCET Instuments
- Action Delivery
Target Group based on Vulnerability
Basic Sectors:
- Artisanal Fisherfolk
- Children
- Farmers and Landless Rural Workers
- Indigenous Peoples
- Persons with Disabilities
- Senior Citizens
- Women
- Workers in the Informal Sector
- Youth and Students
Evaluations
Economic / Financial Effectiveness
The information below shows the costs in utilizing defenses for coastal protection. In comparison to the engineering measures presented, coral reef restoration projects are a much cheaper means of coastal protection. The lifespan of seawalls and breakwaters are highly variable and dependent on the coastal environment, materials used, exposure to waves, and the design [1][5][6]. Seawall: USD 3.3- 18M per kilometer Breakwaters: USD 456-188,817 per meter Coral reef restoration: USD 20-155,000 per meter Coral reef restoration projects would also incur lower maintenance cost because the organism is capable of self-repair. However, reef restoration is relatively new and is suggested to be studied further [1].
Technical Feasibility
Reef systems provide a long-term solution for coastal protection if managed properly. As it is low cost and very effective, efforts are recommended to be channeled to the protection, restoration, and management of these coastal ecosystems. If resources are available, it is suggested that seawalls and other artificial structures be built to add protection against stronger and higher waves. This will add reinforcement to the primary protection provided by the reef systems [6].
Social Acceptability
Eco-DRR projects utilizing coral reefs, seagrass meadows, and mangrove forests are widely accepted as means for coastal defense and wave protection [6].
Environmental Impact
The presence of coral reefs and seagrasses in coastal areas reduce soil erosion by limiting the strength of nearshore currents which promote the stability of the shoreline. Stable shorelines allow for mangroves to propagate, supplementing the coastal protection provided by the corals and seagrasses. All of these organisms also promote biodiversity by becoming habitat and temporary nurseries for other aquatic organisms [2]. Seawalls, on the other hand, could increase the rates of coastal erosion by inhibiting the natural transport of sediments on the shoreline. Components of the seawalls could also be eroded, introducing foreign material to the seas. Continuous erosion of the material would lead to the collapse of these structures [6].
Mitigation co-benefit
Seagrass and mangroves help mitigate climate change by absorbing large amounts of carbon dioxide from the atmosphere. Coral reefs and seagreasses often occur together in the tropics and it was found out that coral reefs aid in the ability of seagrasses to take in carbon input by acting as a barrier from erosion [3].
Keywords
coral reefs, sea grasses, mangroves, seawalls, protection, strong waves, ecosystem-based disaster risk reduction
References