Dredging and the Nantes-Saint-Nazaire Port

The Grand Port Maritime de Nantes et Saint-Nazaire (GPM) is likely the most important economic actor in the Loire estuary.  Along the stretch of the river from the Atlantic Ocean to Nantes, the GPM is responsible for nearly 25,000 jobs.  The Saint-Nazaire-Nantes complex is France’s fourth largest port with nearly 27 million tons of goods passing in and out, 90 percent of which involves facilities at Saint-Nazaire along the north side of the river.  

Portion of Saint-Nazaire Port with Airbus transport ship in the foreground

Last week, as required by French law, the GPM published its strategic plan for the next five years, including plans for 170 million euros in new investments.  Clearly almost anything the Port does will have implications for the estuary environment.  And the planning document doesn’t ignore this.  Virtually a third of its 60 pages are given to “spacial planning and sustainable development” (aménagement et développement durable).

I’ll probably come back to the Port and to more of this document, but right now I just want to highlight one element.  That has to do with dredging.  To provide access to larger ships, the Port dredges along the docks and out into the Atlantic.  It also clears out the channel at several critical points upstream for ships going to the few port facilities at Nantes.

Multiple studies have identified a severe drop in the river’s low-water level as the most serious environmental issue in the estuary.  The combination of sand and gravel extraction, wing dams to concentrate water flow, and dredging to provide ship access has caused the river to dig deeper and deeper into its bed.  Near Angers the bed is about six and a half feet below what it was in 1900; at Nantes it’s about 12 feet lower.

This has had serious consequences, especially between Les Ponts-de-Cé (on the river just below Angers) and Nantes.  Wetland environments in arms of the river have dried up; bridge pilings have been exposed to erosion; the tidal effect carrying salt water upstream has advanced beyond Nantes requiring that city and others to relocate pipes for drinking water supplies.  A massive silt plug between Saint-Nazaire and Nantes seriously impedes migratory fish like salmon and eels.

The GPM plan does mention dredging and promises “to reduce the environmental impact” but is non-specific beyond that.  Also, it’s quite possible that by “environmental impact” the Port is not even referring the effect on the river bed, but to a separate issue relating to disposal of dredged material.

Meanwhile, it appears that a restoration project aimed at the stretch upstream between Nantes and Les Ponts-de-Cé is finally getting underway.  I’ll say more about this in another post.  For now, it strikes me as unfortunate, to say the least, that the Port’s planning document doesn’t connect to the this project.