Summary
BRGM has offices in every region of mainland France and in the French Overseas Territories, in order to meet the needs of its regional partners and help them deal with specific local challenges. Presentation of the activities carried out by BRGM's Regional Division in French Guiana.
Geological map of French Guiana

Carte géologique de Guyane.

© BRGM

BRGM French Guiana is based in Cayenne, where, in addition to offices, it has an archive area, an instrumentation base and a map library open to the public. The Division has a staff of about ten people including specialists in geology and its applications, natural hazards (geotechnical and coastal), groundwater resources (quantity and quality), the environment (pollution, waste management, circular economy) and mineral resources (mines and materials).

In the heart of the Guiana Shield

French Guiana is the only European region in South America. It has Amazonian features and covers 84,000 km², 97% of which is covered by equatorial forest. The population is relatively small, estimated at just over 250,000 people, mainly located along the coastal strip and border rivers. The region's population growth is one of the highest in the world, with an estimated annual rate of 3.7%, meaning the population doubles approximately every twenty years.

The economic activity consists of traditional occupations (wood, fishing, construction, public works, gold mining) and a high-tech sector, driven by the Guiana Space Centre. The unemployment rate is extremely high (21%) and exceeds 40% among young people under 25 (half the population).

French Guiana is part of the Guiana Shield, a vast geological area bordered to the north by the Atlantic Ocean and to the south by the Amazon Basin. More than 90% of the rocks date back to the Paleoproterozoic Era, including the oldest rocks in France (2.2 billion years old). Intense chemical weathering has shaped the landscapes, with alterite formations and lateritic crusts.

Due to the contribution of erosion materials from the rivers of French Guiana and, especially, sediments from the Amazon, French Guiana has one of the most constantly-changing coastlines in the world.

The spatial-planning and economic objectives of the region have been set out, notably, in the "Regional Master Plan for Spatial Planning" (SAR), to which BRGM contributes its specialised expertise.

Public and private partners

BRGM has extensive experience of both public and private partnerships. It works on projects to help shape public policy, or for public and private research in response to industrial requirements, as well as training projects aimed at every level of spatial planning and decision-making in the region: Prefecture, DEAL, DAAF, ARS, the Territorial Collectivity of French Guiana, Communauté d’Agglomération du Centre Littoral (CACL), municipalities and communities of communes, Water Office, ADEME, AFB, University of French Guiana, CNRS, ONF, Météo-France, French Guiana Amazonian Park, Grand Port Maritime, etc.

BRGM also occasionally works with private companies to develop methodologies for Research, Development and Innovation aimed at supporting their various fields of activity. 

Practical information

Taking samples of river water, French Guiana

Water resources: exploiting and protecting the groundwater

BRGM monitors the quantity and quality of water resources and carries out projects to improve knowledge of groundwater in French Guiana.

The challenges

With more than 112,000 km of rivers, French Guiana is ranked among the world's top three countries in terms of the water resources available per capita. However, the resource is unevenly distributed in relation to the population and it is estimated that more than 46,000 people do not have direct access to drinking water today.

A total of 75% of the drinking water supply comes from rivers (compared to 25% from groundwater sources) but this percentage is gradually decreasing. There has been a marked increase in hydrogeological prospecting, since the region has an abundance of high-quality groundwater available and it is cheaper for isolated communities. In densely populated urban areas, groundwater can also contribute to securing and diversifying the drinking water resources. Indeed, coastal rivers are more vulnerable to weather events (saltwater intrusions) and different sources of pollution (materials in suspension and pesticides) and thus require more onerous purification treatment.

Drilling for drinking water in the municipality of Roura

Drilling for drinking water in the municipality of Roura (2017).

© BRGM

BRGM's involvement and responses

In accordance with the Water Framework Directive (WFD), BRGM monitors the pressure and the chemical status of the groundwater masses in the French Guiana catchment basin.

In partnership with local and government authorities and the Water Office, BRGM conducts hydrogeological prospecting programmes and supports local stakeholders in drilling boreholes to develop the use of groundwater for drinking water supplies in areas that are either isolated or that have high population growth.

BRGM also conducts projects to model saltwater intrusion in coastal rivers used for the drinking water supply, monitors river turbidity through remote sensing and assesses agricultural pollution (pesticides in particular) and the presence of metallic trace elements, especially mercury.

And also:

  • A research programme on the presence of iron and manganese in groundwater
  • A thesis project to characterise the recharging process for bedrock aquifers and understand their hydrogeological behaviour.
The Trinité Inselberg, French Guiana

Natural hazards: preventing risks

The region's coastline is vulnerable to coastal flooding and erosion. The areas of the Cayenne Peninsula and Kourou feature rocky outcrops which are subject to ground movements.

The challenges

The areas of the Cayenne Peninsula and Kourou are unique in that they feature the only rocky outcrops along the entire coastline of the Guiana Shield, stretching between the estuaries of the Amazon and the Orinoco. This type of terrain is subject to ground movements linked to episodes of heavy rainfall and due to urbanisation on certain hills, among other things.

The region's coastline is affected by swells coming from the north-east, the dynamics of the Amazon's mud banks and rising sea levels due to climate change, and is therefore extremely vulnerable to coastal flooding and erosion, which can seriously harm the natural environments and coastal infrastructures.

Monitoring of coastal dynamics in the municipality of Kourou

Monitoring of coastal dynamics in the municipality of Kourou.

© BRGM

BRGM's involvement and responses

Since 2014, in conjunction with DEAL, BRGM has been co-managing the Observatory of Coastal Dynamics of French Guiana (ODyC). This is a long-term solution for acquiring, pooling, understanding and exploiting data on coastal dynamics, and a tool for supporting public policies on coastal management.

BRGM helps draw up risk prevention documents (PPR, vulnerability studies, awareness-raising campaigns, etc.) and is involved in crisis management activities.

Since 2017, it has been working with the municipality of Kourou, which is particularly affected by coastal flooding and erosion, in order to develop a management strategy for the Kourou coastline.

In partnership with CNRS, CEREMA and university researchers, BRGM is managing a research project into coastal morphodynamics in the Maroni estuary and into its impact on the ecosystems of sea turtle nesting areas.

And also:

  • Audits and analyses in the event of major incidents involving ground movements and coastal hazards. 
  • Impact of human activities on morphosedimentary dynamics
  • Study of erosion processes on the continental shelf
Operating a gold mine, French Guiana

Mineral resources: meeting the region's needs

BRGM is helping the government authorities and the mining industry to improve methods for characterising and exploiting deposits. It provides its expertise to help determine the location of deposits of construction materials and to promote the green economy.

The challenges

The establishment of a comprehensive set of basic data is essential for research work as well as for applications linked to mineral resources (mining and quarrying).

The need for construction materials (sand, rock, laterites, clays), in response to the strong demographic growth in French Guiana, is another major challenge for the region's development.

Clay sampling in the municipality of Maripasoula

Prélèvement d'argiles sur la commune de Maripasoula.

© BRGM

BRGM's involvement and responses

BRGM is helping the government authorities and the mining industry to improve methods for characterising and exploiting deposits (particularly gold deposits) through good prospecting practices and efficient mining techniques aimed at reducing environmental impacts (turbidity, design of dikes, etc.).

It provides its expertise to help determine the location of deposits of construction materials (sand, rocks, laterites) and to promote the green economy (clay deposits for manufacturing mud bricks). It is also developing methodologies for assessing the recycling potential of secondary materials to promote the circular economy.

And also:

  • Analytical traceability of gold and support for sustainable mining processes
  • Support for managing sand extraction in the Maroni River
  • Updating of the Regional Quarry Plan
Amazon forest, French Guiana

Geology: understanding and promoting local geological heritage

BRGM contributes to the improvement of geological knowledge and its dissemination to partners and the general public.

The challenges

One of BRGM's main priorities is to improve geological knowledge in various sectors, from mineral resources and risks (ground movements) to groundwater resources.

Protecting and promoting the natural and geological heritage of French Guiana is another key challenge in the region.

Students learn about the local geological heritage at the Pointe Buzaré

Découverte du patrimoine géologique avec des étudiants sur le site de la pointe Buzaré.

© BRGM

BRGM's involvement and responses

BRGM contributes to improving geological knowledge and helps pass on this knowledge to its partners and the general public, particularly through its involvement with the University of French Guiana as part of the VALORESS vocational degree course and the publication of the Guide to the Geological Curiosities of French Guiana. It is also involved in the activities of the ORKIDE association, notably in relation to improving practices, publishing professional opportunities and exploiting data.

It has also made data about mineral resource assets publicly available by archiving mining inventory data and setting up a map library.

And also:

  • Prospecting for rock and mineral deposits
  • Identification of hydrogeological potential
  • GEOSOL project: updating of geological maps of French Guiana for the Territorial Collectivity of French Guiana
Papaya farming, French Guiana

Environment: combating pollution, developing the circular economy

The management and recycling of waste on the one hand, and polluted sites and soils on the other, are major issues in French Guyana.

The challenges

Managing and recycling of waste is a major issue, and particularly important in French Guiana, given the limited amount of recycled waste available and the lack of recycling possibilities in the region. In particular, suitable landfill solutions need to be found in the most remote areas and the reuse of materials needs to be encouraged, especially for construction.

Past and present industrial activity (mainly mining) has also resulted in significant risks for the quality of the environment, in particular due to naturally-occurring mercury (and mercury used previously for gold panning) that becomes re-suspended in water, and turbidity.

The management of polluted sites and soils, particularly in agricultural areas under development, requires constant monitoring to reduce the risks of pesticide contamination in zones used for drinking water supply.

Monitoring mercury in water and sediments

Suivi du mercure dans les eaux et les sédiments.

© BRGM

BRGM's involvement and responses

With regard to environmental pollution, BRGM has launched several programmes, particularly concerning mining activities:

  • The mercury flow programme, which studies how mercury used in former mining activities and natural mercury may become re-suspended in water and its impact on the aquatic environment,
  • Monitoring of river turbidity by remote sensing,
  • Identification of techniques for settling suspended materials through flocculation.
  • In the field of waste management, BRGM assists public authorities in finding waste storage sites and helps monitor the environmental impact, particularly on isolated sites.

And also:

  • Contribution to the Regional Health and Environment Plan.
  • Emergency operations to deal with accidental pollution, in support of the Water Police.
View of coastal erosion along the beaches at Rémire-Montjoly, French Guiana

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