Water shapes our environment as it flows from source to sea. This essential element—both peaceful and turbulent—created the conditions for life on Earth to emerge. While water covers 70% of the planet, continental water ecosystems represent less than 1% of that total. Given the vast diversity of geological and human-influenced contexts, understanding these environments is critical.
The site in the photo is the location of an experimental rewilding project to restore the sandy beach after removing ripraps built with tons of blocks.
Today, 50% of the world’s population live within 100 km of the coast, a figure likely to rise in the coming decades despite climate change. As a result, hydrographic and topographic data near the coastlines has become strategically vital. These insights help monitor coastal development and identify flood-prone areas, knowledge that is increasingly indispensable.
Between 1980 and 2024, extreme weather events caused approximately €822 billion (about $890 billion) in economic losses across the European Union.
At YellowScan, we believe Lidar technology for UAVs delivers more than just data; it also provides actionable intelligence.
“Extreme climate conditions now demand a new discipline from European regions: faster decision-making, but on a stronger foundation. In this equation, aerial data is no longer just a technical tool for experts. It has become a quiet cornerstone of economic stability, intersecting urban planning, public finance, and collective security. With risks set to persist, better measurement isn’t a luxury—it’s a governance requirement.” — Tristan Allouis, Founder and CEO, YellowScan
The YellowScan team supports researchers in the field with the deployment of the topo-bathymetric Lidar YellowScan Navigator.
Lidar Technology: a game-changing advancement
In recent years, the mapping industry has undergone a major transformation thanks to Lidar. Deployed from aircraft, this laser-based technology measures precise distances and creates accurate 3D digital models of reality—even through vegetation or water. As part of France’s national Lidar HD programme, the IGN (National Geographic Institute) produces and freely distributes 3D maps of the entire country’s surface and subsurface. These datasets are invaluable for local government authorities, particularly those lacking resources to commission custom surveys.
On the left, the Lidar HD base from the campaign in 2025 with the ripraps in the estuary. On the right, the new situation without the ripraps just after the works to remove the blocks. The YellowScan Navigator created a new dataset with the topography and the bathymetry in two hours of flight to cover 56 hectares.
Case study: restoring coastal sand flow with topo-bathymetric Lidar
The YellowScan team supported a rewilding project led by CEFREM (Center for Training and Research on Mediterranean Environments), a joint research unit in geosciences, oceanography, biology, ecology, and sedimentology affiliated with the University of Perpignan Via Domitia (UPVD) and CNRS. The project aimed to restore the natural flow of sand along the coast.
In the 1970s, ripraps (artificial rock barriers) were constructed to stabilize the estuary of a small river, halting the movement of thin sediments. Fifty years later, the effects are measurable: sand has accumulated south of the ripraps, while the northern beach has eroded by one metre per year for the past two decades.
Three views of the dataset processed with the YellowScan CloudStation. In the Colourization and Classification views, the water class is shown. In the Elevation view, the water class is removed; the colour variations made it possible to identify the deepest places in blue and the sand bars in orange and red.
To monitor these changes, a baseline dataset (T0) was created before the restoration work began, using multiple methods:
Bathymetry with an echo sounder
Drone photogrammetry
Topographic and bathymetric Lidar
Data acquisition was coordinated within 24 hours to minimize topographic and bathymetric changes during the survey. After weeks of wind, the sea was calm and the turbidity was not so important. The researchers decided to coordinate the different acquisitions in a short time to compare the different methods and technologies with a minimum of changes due to the wind and streams.
Mission specifications
Study area: 56 hectares
Number of flights: 6
Drones: DJI M600 and M400
System: YellowScan Navigator
Altitude: 60 m maximum (near an airfield)
Overlap: 50%
Point density: >20 points/m²
Highest point: 3.5 m
1 Secchi depth: 2.2 m
Maximum underwater depth reached: -5.38 m
Comparing datasets: before and after riprap removal
A key challenge in coastal monitoring is connecting topographic and bathymetric datasets. Traditional boats cannot safely approach shallow shorelines, often leaving critical gaps between land and sea data. Topo-bathymetric Lidar bridges this divide, creating seamless datasets that integrate both environments.
On the left, the topo-bathymetric dataset from the YellowScan Navigator, on the right the bathymetric dataset from the echosounder. The elevation colourizations revealed the underwater depth variations. We can easily identify the similarities between both datasets with regard to the biggest sedimentary bars. In this case, the northern part may move a lot to restore the sandy cost thanks to the rewilding works.
In this project, the YellowScan Navigator captured data before (2025) and after (February 2026) the ripraps were removed. The Lidar HD base (2025, shown in green) was overlaid with the Navigator dataset (2026, shown in blue) in YellowScan CloudStation using LAS files to detect changes.
This view shows a slice in the overlay of Lidar HD base [EP1.1]with the Navigator dataset. It is easy to show the first changes after removing the blocks of the ripraps. We can observe in blue the new topography with the bathymetry in a seamless dataset.
The results were impressive:
The new topo-bathymetric dataset revealed subtle shifts in underwater topography.
Without the water surface, comparisons with the echo sounder bathymetric base became possible.
Elevation colourizations exposed underwater depth variations, highlighting similarities between the Lidar and echo sounder datasets, particularly in large sedimentary bars.
The northern section, which had previously eroded, now shows signs of restoration thanks to the rewilding efforts. Future missions will repeat the same flights to assess long-term benefits, creating new seamless datasets from coast to sea.
Advantages and limitations
Topo-bathymetric Lidar is a highly effective tool for scientists monitoring coastlines. Its ability to merge topographic and bathymetric data fills critical gaps left by traditional methods. However, two key limitations remain:
Water turbidity can reduce laser penetration, affecting data quality.
Mission scale must be carefully planned to ensure coverage and accuracy.
Despite these challenges, the technology’s ability to connect land and sea in a single, comparable dataset makes it invaluable for erosion monitoring, flood risk assessment, and coastal management.
Conclusion: a new era for coastal monitoring
As climate change intensifies, the demand for precise, actionable geospatial data will only grow. Topo-bathymetric Lidar for drones is not just a technological advancement—it is a necessity for sustainable coastal development. By providing seamless, high-resolution datasets, it empowers scientists, governments, and communities to make informed decisions in the face of an uncertain future.
View with Ripraps
View without Ripraps
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