Erosion is the loss or displacement of land along the coastline due to action of wave, current, tides wind-driven water, or other impact of storm or tropical cyclone, it also means the loss or displacement of land due to the action of wind, runoff or surface water or ground water seepage.
Why does coastal erosion need to be managed?
In Seychelles there are three main reasons why the coast needs to be protected and they are environmental, economical, and social.
Environment: Natural protective features i.e. beaches, and dunes within coastal hazards areas provide buffering and protection to shore lands from erosion by absorbing the wave energy of open water, the sheer force of the water can be
damaging to plant life and can destroy habitat, on the dune and can disrupt the whole coastal ecosystem, the eco-status of our coast and shore is highly important for the wellbeing of all Seychellois.
Economic: The tourism industry is one of the main pillars of our economy and most of our hotels are located on our coastal areas. Coastal erosion, with other common phenomena like sea-level rise and climate change has a direct impact on this industry. Our Beaches are being damaged, business may shut down and jobs are at risk.
Social: About 30% or more of our population lives on the coastal zone. Houses and buildings are threatened by the rapid coastal erosion, house prices will increase and they may refuse or deny house insurance cover due to the increase of the risk of erosion, power stations and other critical facilities near coast are in critical status due to the loss of land , many will face closure or relocation, farmlands lost and salt intrusion may reduce yield which also causes drop in income.
Severe beach erosion at Anse La Mouche
(Coastal erosion is silent killer that is effectively taking away the life of coastal region over Seychelles)
Coastal erosion are cause by many factors, including natural processes and human induces activities, the aforesaid mentioned are briefly discuss.
Natural causes of coastal erosion.
Coastal erosion is a natural phenomenon , an endless redistribution process that continually changes beaches, dune and bluffs wave currents tide wind driven water, rain runoff and ground water seepages all move sand , sediment and water along the coast.
Other contributing factors that can significantly increases coastal erosion of a natural protective feature include length of fetch, wind direction and speed, wave length, height and period, nearshore water depth tidal influence and overall strength and duration of abnormal event i.e. cyclones and storm surges.
A combination of these factors and events can amplify these effects by increasing water level, increase storm surges, increasing the distance wave reach inland and producing damaging waves; along the shore scouring beaches and dunes area reducing sand from beaches and allowing water and wave action further inland intensifying coastal erosion of beaches and dunes.
Human causes of coastal erosion
Human activities. Such as construction, shipping, boating and recreation can increase coastal erosion of sandy beaches, and dunes.
Even though natural events play a major role in coastal erosion process human actions can intensify the effects of these process and speed up the coastal erosion process.
Human’s contribution to the coastal erosion process are:
- Removing vegetation, exposing bare dune to be easily eroded by wind and wave action and water runoff
- Directing runoff from roads parking area and others location over the dune edge causing it to erode
- Constructing hardened structure on the shore that block movement of sand along the coastline, reflect wave action onto adjacent shoreline. Or cause deepening of nearshore area, those structure also change current pattern
- Building without considering the potential for damage to property or natural features
- Activities which destroy natural protectives features such as dune and vegetation
Erosion control measures tried in Seychelles
The commonly employ method are:
1. Hard Erosion control measure, Hard erosion control measures which has been used are Groins more visible at Anse Keralan Praslin, use to deflect tidal current away from shoreline and control movement of beach material, Rocky armouring at Anse La Mouche Mahe, large rocks place at the sea edge used to absorbs wave energy and hold the beach materials, they serve as semi-permanent infrastructure, these structure are not immune from normal wear and tear and will have to refurbish or rebuilt, they have a life span.
Rock Armour at Anse La Mouche Mahe, protecting both the shoreline and infrastructure
Disadvantage of them is that they deprive public access to beaches and drastically alter the natural state of the beaches, they can alter or reduces the interval of natural beaches nourishment process, and sand movement with current and season, expensive to build and maintain.
2. Soft erosion control measures
Soft erosion strategies can also refer to temporary option of slowing the effects of erosion, these including sandbags, artificial beach nourishment, and bollard and picketing to make barriers like wall, dune reforestation with native species, and maintaining native vegetation such as mangrove, and veloutyer .
Wooden poles erected to build wall like structures to protect shoreline, from wave energy
Moving human and cancelling all activities in the affected area of the coast and surrender the coast to the natural process of the ocean and the environment, relocation could also simply mean moving human and its activities further inlands.
Proposed Measures to prevent and reduces coastal erosion
- Promoting and preserving the natural protective features, such as dunes, and vegetation
- Restricting and prohibiting activities or development in natural protective feature area
- Ensuring new construction or structure are a safe distance from areas of active coastal erosion and impacts of storm surges
- Political accountability
- Clear role and responsibility in coastal zone management of Ministries and line agencies
- Provide suitable access point for beach users and appropriate parking bays.
- Reviewing coastal Management policies or act to suit our local circumstances
- Take long term views in planning ahead for the future to ensure that current management system will have long term benefits for the coast.
- Restrict development of the undeveloped coast
- Develop a comprehensive educational and communication programme aimed at all level, (Government, local, private, schools E.T.C) to increase awareness about Risk due to coastal erosion , and extreme wave condition and their environmental implication
- Encourage soft engineering solution in affected areas
If you have a beach property you will not be able to leave to your children as an inheritance because it will be at risk of erosion or underwater, unless you take proactive measures of addressing these risks.
Mr. Cliff Alissop
Senior Disaster Management officer
Department of Risk and Disaster Management