Climate change and population explosion are two major problems facing our beautiful planet today. These problems, which are accompanied by multiple challenges, have all the more impact on coastal zones and their particularly fragile and vulnerable ecosystems. Rising sea levels are the major issue affecting these environments. It is an aggravating factor in many phenomena such as coastal erosion, flooding and saltwater intrusion. Paradisiacal landscapes are often transformed by the repeated assaults of the forces of nature and human action into chaotic and unlivable places. Developing countries are less able to deal with this situation because of their conditions.
B- Choice of site
Our attention was focused on Africa, a continent with great potential which, although abundantly endowed with resources, already faces many other problems (poverty, precariousness, ...).
And as macroeconomists tell us, Africa will be responsible for a large part of future exponential population growth and will be home to about a quarter of the world's population in 2050. Moreover, with 46 per cent of its population living in extreme poverty, a fraction of 38 coastal states out of its 54 countries, and the sea swallowing in some areas more than 10 metres per year, the situation is all the more intriguing. It is all the more intriguing because of the situation of the populations of these regions, who depend mainly on the sea for their livelihood. This situation has become so urgent in recent years that crossing the Mediterranean by canoe is becoming an option. Faced with this situation, we see the need to act.
We have chosen the 700km long Senegalese coastline (a great asset which today seems to be more of a problem), of which more than 90% are low, sandy beaches and therefore vulnerable to coastal erosion. Studies and observations carried out by specialists have permitted us to identify 50km that are more vulnerable. This is the cumulative distance covering areas such as Saint-Louis, Dakar, Rufisque, Bargny, Saly, Joal and Casamance with islands such as Djogué and Carabane. This is why Senegal has identified the issue of coastal erosion as a priority related to climate change.
Senegal is one of the most affected countries in Africa and in the world and its main economic activities are directly related to the blue economy. Succeeding in preserving such a vulnerable and fragile coastline would certainly be a major step towards solving climate change-related problems at the international level. Moreover, the country owes its name to the river that borders it to the east and north and which has its source in the Fatou Djallon in Guinea. The relationship to water is therefore very important for the identity of the country and even more so for the towns and villages in the coastal area.
C- Analyses, effects of coastal erosion
- Offshore: activities on the water very little developed. These are essentially fishing and transport, which are sometimes very threatened by swell (fishermen sometimes go for months without going out to sea). There is also a lack of maintenance and protection of the sea, which is heavily polluted by plastic waste.
- The delta: There is a progressive degradation of the coral reef and mangrove followed by a strong retreat of the coastline and a serious disturbance of the deltas' ecosystems.
- Beach and coastline: Disappearance of the dune cord, anarchic seaside construction. The presence of buildings is very exposed to swells, some of which are half-destroyed and which we will describe as dangerous.
- Inland: Presence of wastelands and unused land forming hollow spaces in the city, which favours insecurity and the creation of dumps or slums. There is also a loss of arable land due to the phenomenon of salinisation. Flooding of some inhabited areas.
It will therefore be a question for us to be part of a protection scheme that integrates the development of the coastline. We will therefore take into account protection, development, sustainability, economy, and all activities related to the coastline and the blue economy.
A- Challenges & Problems
- Raise awareness of the use of local environmentally friendly materials rather than commonly used marine sand.
- Protecting the most exposed populations and improving their living conditions
- Bringing people closer together through culture, sharing, exchange, activities and concerns related to the coast.
- Preserve the shoreline, be aware of the coastline, prevent sand from moving inland from the coastal system.
- Control swells, break them, break them by introducing friction, thus preventing sand from being swept out to sea.
- Fostering the development of biodiversity
- Diverting human attention from profitable and unsustainable activities to very sustainable, profitable and resilient activities
- Propose solutions that are part of a protection strategy that integrates the development of the coastline.
How can we protect ourselves from the sea while opening up to it? How to protect man from the sea's assaults while bringing him closer to it? How can we make people more sensitive to the sea, the coastline and above all to the environment? How can we protect the coastline without creating segregation between land and sea? How can the coastline be developed for human flourishing while guaranteeing its development and sustainability? How can we control swells while promoting the development of biodiversity? How can coastal development be integrated into the protection programme? How can we move from life with the sea as a struggle to live with the sea as a symbiosis?
B- Approach: observing nature and listening to humans
We believe that the more complex a problem is, the more we need to approach it with simplicity.
The living world as a model: In this case, what would nature do?
Why didn't it happen everywhere? Why are some areas vulnerable while others are very resilient?
So, rather than throwing ourselves headlong into thinking about affected areas, our strategy is to start by observing and analyzing naturally resilient areas.
What we find is that all low, sandy, resilient coastlines are protected by islands (acting as natural breakwaters) that protect them from swells, thus ensuring that local residents flourish and biodiversity develops. In front of Yoff Layène, is the island of Yoff which protects all this part. All the swells which were to hit Yoff, are diverted by the island of Yoff. The island of Ngor does the same for the eponymous beach and Soumbédioune is protected by the Magdalen Islands. As for Ouakam, its beach is protected by a small submerged islet, called the lying marabout. The Rufisque landing zone was established behind a natural rampart.
The different interventions are organized into five steps:
- The demolition of ruins and dangerous buildings near the waterfront will free the beach and reduce the phenomenon of subsidence.
- Ecovillages made of local materials will relocate internally displaced populations on open land. These new living spaces will provide them with a fulfilling living environment, but will also constitute a kind of appeal, raising awareness of the use of local materials such as earth, bamboo, wood, stone... unlike the sea sand frequently used by the populations to build. In addition, a deep reflection was made on the shape of the new dwellings. We have proposed housing modules that anticipate the future needs of families through a possibility of extension that will allow each family to develop its housing according to its tastes, its finances, its needs while appropriating it and personalizing it. The homes will be energy self-sufficient thanks to the exploitation of solar energy.
- The use of windbreaks and adapted plant species will enhance, stabilize and then biologically fix the dune line on the beach. This natural restoration of the dune line is accompanied by the creation of a resilient park. This technique effectively recovers sand that is blown inland by the wind.
- The creation of coral reefs and the restoration of mangroves promote the development of biodiversity, the attenuation of waves and optimize the deposition of sediments in the deltas.
- The creation of artificial islands breaks the swell and prevents sand from leaving the coastal system while developing economic and social activities. These islands can also be used as a quay for maritime transport, as places of tourism with hotel establishments, as a nursery with the development of biodiversity linked to the reef, as a play and leisure area, ... The foundations of the footbridges leading to the islets are designed to stabilize the beach and shallows, optimize sediment deposition and create walking areas with spectacular views of the landscape and offering exciting experiences, without disturbing coastal drift.
- An extension at sea, through floating architecture, aims to optimize activities related to the blue economy while respecting the environment.
Thus, as the sea advances, we emerge. Life with the sea ceases to be a battle and becomes a symbiosis.
SEME-BIOSE is a pilot project in which we propose an alternative based on a "land-sea" approach. The aim is to be part of a protection scheme that integrates coastal development through a set of strategies both on land (dunes, ...) and in the water (reefs, ...) that will reduce wave action, prevent erosion, generally rebuild the coast and promote the blue economy. The project aims to enhance the economic, social and ecological resilience of the populations of the Senegalese coast.
The origin of the title comes from a deep desire to launch a call! Not only a call to action but above all a call to conscience because sowing seeds is an investment for ourselves and for others. We want to sow in the hearts of men the values that will make them responsible and virtuous citizens. This title also refers to the symbiosis that we put forward in our project, between blue and green, between land and sea, but above all between man and nature.
The project can be summarised as follows: SEME for awareness, investment, action to anticipate the future and BIOSE for Biodiversity, Integrity, Order, Synthesis, Emergence are the qualifiers that best define the project; hence the title "SEME-BIOSE".
A- Constructive methods
- For the islets, tetrapods and trapezes will be used. The technique used is innovative and the result of multiple studies and experiments conducted by geologists. It makes it possible to build durable and nature-friendly structures at much lower costs than anything already being done in terms of protective structures. Tetrapods (2.4 metres high; 4.5 tonnes and 2 to 3 cubic metres of volume capable of withstanding pressures of eight storeys) are used to break up swells while trapezoids are used to accumulate sand. The tetrapod is a reinforced concrete block made of four truncated cones assembled by their bases, used more particularly in engineering with a curved profile and calculated in such a way that it minimizes the impact of marine flows. For their manufacture, techniques have been developed to exploit mining waste.
- The coral reef is replenished with low ph marine concrete blocks specially designed to provide fish habitat. Their geometry optimizes wave attenuation.
- The housing of the eco-domains, as well as the rehabilitation, will be made of local materials (...) while also exploiting the rubble from the destroyed buildings. Local construction techniques will also be promoted.
- The structure of the floating trusses will be made mainly of bamboos and wood, light and flexible materials offering multiple opportunities compared to other materials sometimes used. Moreover, they are ecological and warm materials. The hull will be made of an innovative material made from recycled plastics. This set will be based on a platform based on an ancestral principle, that of rafts. The floats used are recycled plastic drums (cylindrical in shape) assembled with wooden beams.
- Artificial islets are the result of mimicry of naturally resilient areas where the presence of natural islands helps to break swells while promoting the development of marine and terrestrial ecosystems.
- Biomimicry has also led us to explore innovative, simple and zero energy solutions to produce resources such as freshwater, a resource that is becoming increasingly scarce due to saline intrusion. We drew inspiration from the Namibian scarab (a small beetle living in the Namibian desert and having developed a rather ingenious strategy to produce its own freshwater) to supply the different parts of the project with fresh water, especially the farms, which will be able to be completely autonomous in freshwater without spending energy and without producing waste. Nets made of recycled plastic and old fishing nets are integrated into the buildings to produce fresh water from the humidity of the air while protecting the buildings from extreme heat. Small oases are created through small towers using the same principle to provide people with fresh water on a daily basis. Similarly, the use of a new recycled plastic-based material and ETFE film (Ethylene Tetra-Fluoro Ethylene) for the shell of floating farms collects moisture from plant perspiration through condensation. Fine droplets of freshwater form on the inner (rounded) wall of the structure’s shell and run off to the base where they are collected and stored in tanks for reuse.
As a result, farms become self-sufficient in freshwater without consuming energy.
- The symbiosis visible at all levels of our project has been inspired by natural processes and ecosystems.
- The architectural forms of the eco-domain housing and floating structures are mainly based on bioclimatic principles. They make it possible to make the most of nature while respecting it. The natural light and ventilation inputs are optimized for the development of humans and ecosystems created in the project through the farms. New types of materials make it possible to exploit the most accessible natural resources in the project environment in order to transform them into opportunities to compensate for the scarcity of certain resources such as freshwater.
D- Ecological principles
- Turning problems into opportunities through the recycling of plastic waste and drums, mining waste and landfill waste that is used as construction materials.
- Exploitation of accessible renewable energies (solar energy) through solar farms.
- Freshwater production without energy consumption
- Water pollution control and cleaning
- Reforestation and public awareness
- Creation of virtuous cycles (vegetable fish, ...)
- Association of vegetable gardens with each housing module; this has a social and economic value.
- Reducing the impact of trampling on the beach by creating gentle traffic lanes.