Drones surveying damage to the West African coastline

None of the drones being used to map out the scale of land degradation on the west African coastline have yet to endure the drowning ordeal this legend had to suffer through in Lake Michigan, USA, last year, but the Phantom 4 Pros are doing a really great job telling the story of how the coasts in West Africa – a source of livelihood for millions of people – are claiming land in the area.

The coast of West Africa. Home to about a third of the nearly 300million-strong total population that belong to the region’s seventeen countries blessed with a coastal frontier as part of their borders – the coastal citizens of Benin, Cote d’Ivoire, Ghana, Guinea, Mauritania, Nigeria, Sao Tome and Principe, Senegal, Togo and eight other countries are engaged in shoreline industrial activities that are credited for bringing in 56 percent of these countries’ gross domestic product every year.

It therefore goes without saying that looking after the coast should be a priority for the people who live along it, given how indispensable it is to their daily lives. Right?

Alas, it is easier said than done.

According to statistics provided by the World Bank, which launched the West African Coastal Areas Management Programme (WACA) in 2018, about 13,000 people lost their lives to flooding and pollution in the area in 2017.

“Coastal erosion and flooding in West Africa severely threaten people’s communities, livelihoods, safety and investments. About 56 percent of West Africa’s GDP is generated in coastal provinces, where one-third of the population resides,” WACA says on its website. “Stronger storms and rising seas are wiping out homes, roads and buildings that have served as landmarks for generations. Some beaches are deeply mined for sand, protective mangroves are deforested, and people are increasingly vulnerable to the impact of climate change. Some residents have no choice but to move away — a trend that is breaking up communities and changing the social fabric for future generations.

“Rapid and often unplanned urbanisation has devastated the natural landscape that once served as a buffer for erosion and flooding. These developments disproportionately affect the poorest and most marginalised, and will intensify due to climate change.”

Besides costing human lives, the economic cost of flooding, air and land pollution as well as erosion disasters on the coastline is now running into billions of dollars – 3.8billions of them to be exact. More than half of the coast in the area is losing its hairline at a rate of 1.8 metres every year.

It is a situation that needs urgent arresting.

And this is where WACA and drone technology make their entrance.

Bargny, Senegal: Coastal citizens can no longer afford to lose more territory to the sea. Picture: World Bank

A brainchild of the World Bank in partnership with West Africans who live along the coast and depend on it for their livelihoods, nutrition, food security, and economic prosperity, the WACA program supports countries’ efforts to improve the management of their shared coastal resources and reduce the natural and man-made risks affecting coastal communities.

Currently with nine participating countries, its main aim is to boost the transfer of knowledge, fostering of political dialogue among countries, and mobilising of public and private finance to tackle coastal erosion, flooding, pollution and climate change adaptation.

“While countries have started to contain erosion and flooding, there is an urgent need for partners to mobilise financing through coordinated regional action,” WACA says. “Collaboration at the policy and technical levels helps countries to manage erosion hotspots, and to maintain the livelihoods that a healthy coastal ecosystem provides to people and economies.”

As part of this program, a littoral survey was conducted last year in Togo and Benin – covering more than 60km of the shared coastline between the two countries – which sought to digitalise the state of the fragile coastal ecosystem and update the hitherto non-existent or poor technical data with fresh ortho-images and accurate topographic data.

To achieve those goals, we decided to launch an international team with bi-frequencies GNSS, Phantom 4 Pro and Phantom 4 Pro RTK drones, and an operational ground team,” said Burnoit Guillot, Drone Manager at Artelia, in his presentation at the DJI Airworks Conference 2020 last year. “A bathymetric survey during this mission also acquired sub-water topographic data of the specific tidal area.”

With headquarters in Paris, France, Artelia is a multinational engineering consultancy firm offering solutions to the construction, maritime, environment, energy, transport and urban development industries. Its drone wing, Artedrones, provides an array of aerial data acquisition services, ranging from assistance to project owners to the design and implementation of a complete data acquisition plan.

“We also operate our own drones when our in-house teams and equipment match all of the client’s requirements. Our experts then summarise and process the aerial data collected, to provide a pertinent interpretation and analysis of the issues at stake.”

Guillot said his company chose the aerial drone survey solution for its Benin and Togo mission because of the mobile, highly sensitive nature of shorelines, which he says require non-intrusive and cost-effective survey protocols.

“UAVs are flexible, as they do not need to launch any planes or rockets; and they can be improved across time, as new technologies like RTK and integration on dual frequency antennas come into existence. Drones can also fly regardless of weather conditions like wind and cloud cover, aside from their capability to survey large areas.

Burnoit Guillot

“Not to also mention that drones are very easy to transport, and are also very efficient at saving time – we covered extensive surveys across the 60kms of coastline in only one week.”

The two week-long flights resulted in the snapping of 10,000 aerial photographs, three hours’ worth of video rushes and seventy 360 panoramas, which data was then processed before being presented to WACA. The project itself is still ongoing, because Artelia recommends that such surveys be done on a regular basis to help with accurate data about the recovery – or lack thereof – progress being made in the affected areas.

“Our engineers will use the drone data for dense point cloud extraction, and 2D shoreline position would be established using photo-interpretation of drone imagery,” Guillot said, adding that the processed data would be used to simulate waves with 2D/3DH models, simulate shoreline changes with regard to rising sea levels, as well as power storm impact and flooding simulation models.

These simulations will help the local authorities to anticipate potential issues that can be triggered by climate change and design sustainable solutions to mitigate their effects. Such solutions include increasing resilience along the coastline through fixing dunes, restoring mangroves, and replenishing beaches. There are also growing calls for the creation of green jobs in nature conservation, flood management and house retrofitting to reduce pressure on coastline dependency.

In worst-case scenarios – as once happened in Sao Tome and Principe – WACA has had to negotiate with residents to move to safer resettlement areas.

Going forward, Guillot said it would be great if they could transfer their expertise to local entrepreneurs, who will then be armed with the right technology and knowhow to monitor the coasts that give them a livelihood.

“Our goal is to empower the locals to undertake similar missions every year and help them build a database of annual variations in the coastal areas. This will inform their planning process. We are looking at sharing our best practices and protocols for drone flying and teaching the local authorities the best ways to process the data and leverage it to the fullest.”


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