Unusual lake in a forest

In the Raismes forest in northern France, a 100-hectare lake sits in the middle of a black slate base, surrounded by birch trees that appear almost unnaturally white. This striking landscape was not present on any map before the twentieth century and was created by an industrial accident that has since transformed into a natural sanctuary.

Origin of the lake

The lake, known as Mare à Goriaux, was formed by mining subsidence that began in 1916. This process created three ponds that eventually merged in 1930 to form the lake. The area is now a Domain Biological Reserve managed by the National Forest Office and hosts nearly 300 bird species.

Mining history of the area

The Anzin Mines Company, one of the most powerful coal exploiters in northern France at the turn of the twentieth century, expanded its operations into areas that were thought to be protected, such as the Raismes-Saint-Amand-Wallers forest. Miners worked from the Arenberg pit in Wallers, digging deep for coal, which led to subsidence and the eventual formation of the lake.

Formation of the lake

As the ground continued to sink due to the emptying of underground galleries, the terrain allowed groundwater to rise to the surface. The three ponds grew and merged in 1930 to form a single body of water. To prevent the water from expanding further and threatening nearby infrastructure, a spoil heap known as the Arenberg Dyke was built in the 1970s.

Ecological transformation

What began as a landscape wound caused by mining has become a refuge for local wildlife. Classified as a Domain Biological Reserve in 1982, the Mare à Goriaux is now a unique landscape with a striking visual contrast between the water, birch trees, and the dark soil of the spoil heap. It is especially significant during autumn when migratory birds use the pond as a stopover.

Broader regional impact

The transformation of Mare à Goriaux is not unique. Similar examples exist in the region, such as the Rieulay area, where an old slate mining spoil heap was converted into an ornithological reserve and a swimming base. These examples highlight the ability of former industrial sites to be reborn as protected natural areas.

National and international recognition

The Mare à Goriaux is part of the Northern Nord-Pas-de-Calais Mining Basin, which is inscribed as a UNESCO World Heritage Site. This recognition honors both the industrial past of the area and its ecological resilience. The site serves as a reminder of how human activity can leave lasting scars on the landscape, but also how these areas can be transformed into thriving natural spaces.