Lac Des Plagnes Picture ArticleA fascinating glacial history
Between 75,000 and 20,000 years ago, the valley was shaped by the passage of glaciers, creating rocky locks, flat areas and umbilicals (glacial depressions). The Ardens glacier, descending from the Chavache ridge, eroded the rocks and transported sediments as well as erratic boulders, stones or rocks that fell from the top of the mountains to the surface of a glacier and were carried by the movement of the glacier some distance from its point of origin.
When the glacier melted, it left behind morainic deposits, an accumulation of rock debris (till) carried or deposited by an impermeable glacier covering fissured rock. This led to the formation of two lakes: Lac des Plagnes and Lac de Cubourré, fed by streams flowing down from the Pointe de la Chavache.
Over time, the rocks and sediments transported by the streams gradually filled in these lakes. Today, Lac de Cubourré has been transformed into a wetland, while Lac des Plagnes has become an artificial lake fed by a waterfall from Cubourré.
For more details on the geological history of the lake, see pages 44-45 of the booklet ” Les lacs du Chablais “.
A Rich and Diverse Ecosystem
Lac des Plagnes is a haven for many species of flora and fauna:
- Flora: Slender cottongrass, Incarnate orchid, Marsh epipactis.
- Fauna: Red-legged frog, Hastate agrion, Great aeschne, Common pipistrelle, Whiskered murre.
For more information on the site’s biodiversity, please consult the Chablais Lakes brochure.
Whiskered Murin @p.amiard
Epipactide Des Marais @e.sansault
Great Aeschne @b.piney 
Common Pipistrelle @marenwinter
Linaigrette Grele @y.martin
Agrion Haste @f.jiguet
Red Frog @f.serrecollet
Lake Plagnes Abondance A protected site: ENS label
Lac des Plagnes has been awarded the “Haute-Savoie Nature” label as a Sensitive Natural Area (ENS) for 99 years, in partnership with the Department of Haute-Savoie. Environmental management of the site is the responsibility of the Pays d’Évian – Vallée d’Abondance Community of Municipalities (CCPEVA).
The objectives of the management plan are to
- Preserve the wetlands to maintain biodiversity and ensure their ecological role (water, pollution control, CO2 storage).
- Reconcile tourism and nature conservation: The site welcomes around 35,000 visitors a year, attracted by its spectacular scenery and numerous hiking opportunities.
To improve accessibility, a cycle path was laid in March 2024, allowing visitors to walk safely around the lake.
What the eco-guards say
Since the creation of the cycle path around Lac des Plagnes, the eco-guards have observed an increase in visitor numbers, enabling a wider public to enjoy the site in safety. However, this has had an indirect impact on biodiversity:
- Environmental impacts: Campfires, stones thrown into the lake, dogs running loose in the surrounding forests, unauthorised swimming and the picking of protected plants.
- Disturbance of agricultural areas: Dogs roaming the mountain pastures disturb the herds. In addition, uncontrolled car parking makes it difficult to access farm machinery.
- Difficult cohabitation: The diversity of users (families, mountain bikers, anglers, hikers, walkers with pets, bivouacers) sometimes leads to conflicts of use.
The work carried out in 2024 is just the first step in improving the reception for the public and preserving the site. Awareness-raising campaigns and additional development work are under way to ensure that visitors, wildlife, flora and local farming activities live together harmoniously.
Lac Des Plagnes June 2017 05
