France: Testing the waters

France: Testing the waters

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Airborne LiDAR bathymetry helped understand the coastal zone and enhanced the economic and environmental activities in the zone

In February 2012, the General Council of Finistère and Regional Council of Provence-Alpes-Côtes d”Azur in France commissioned an airborne LiDAR bathymetry (ALB) survey project for precise understanding of the coasts. The area of interest included more than 2,000 sq. km. of complex rocky coastlines, beaches, islands and reefs along the French coastlines of Finistère on the Atlantic and the Provence, Alpes and Cotes d”Azur in the Mediterranean. The surveys were also supervised by France”s Service Hydrographique et Océanographique de la Marine (SHOM) as part of the Litto3D programme.

The survey supported a wide range of stakeholders involved in:

  • Risk prevention including flood inundation and tsunami mapping
  • Shoreline management including erosion and sand nourishment to get a better understanding of the erosion process
  • Economic development for ports, tourism and marine energy
  • Habitat mapping for biodiversity

The survey was conducted using the Fugro LADS Mk 3 ALB system that has been integrated with the recently developed Riegl VQ-820-G shallow water ALB system. Both ALB systems utilise sophisticated 532nm lasers to safely and efficiently measure water depth and collect data over the marine and coastal zone environments.

During the survey, the two systems operated simultaneously from a single fixed wing aircraft and complemented each other by providing coverage on the coast and offshore to deep water. The combination of the two sensors provide a seamless and high resolution description of the land-sea interface, while still achieving coverage in the depths >20m offshore.

An additional benefit of ALB technology as a survey tool is that it offers the operational flexibility of an aircraft being able to freely move within and between survey areas to avoid unsuitable environmental conditions. The survey planning for this project took into account the environmental conditions of Finistère where spring kelp growth curtails acquisition by airborne LiDAR systems and the Atlantic Coast weather is not always suitable. PACA also presented survey challenges with commercial and tourism activities in the summer months, limiting survey operations. Alternative areas were assigned where possible to minimise the impact of adverse environmental conditions. Unfortunately for this survey, aircraft maintenance restrictions also impacted the operations and reduced the flexibility of moving between the Finistère and PACA areas.

The task of combining the two sensors for this survey was certainly challenging and pushed the limits of the standard tools and methods used. It required adaptations to the data collection and processing strategies, along with enhancements to both systems” software architecture and algorithms that ensured a seamless integrated dataset from both systems. Fugro was able to provide complementary survey and engineering expertise to provide an efficient low-risk survey approach to these environmentally challenging but economically important regions.