The lake of Longemer ends in a rich delta formed by the Saint-Jacques stream. Water lilies and aquatic grass beds line its bottom and surface. Between wet meadows, spruce forests share the territory with marshy alders and ancient peat bogs. Next to Bilon's hill, the mountain elms bear witness to the diversity of the soils. Rich and varied fauna and flora unfold there. The delta is protected under the policy of the Sensitive Natural Area of the Vosges.