Definition: A lake or estuary that is formed at the mouth of a river where flow is blocked by a bar of sediments. It can be maritime (the bar being created by the current of a sea) or fluvial (the bar being created by the flow of a bigger river at the confluence).
Definition: Gravel is an environmental material which is composed of pieces of rock that are at least two millimeters (2mm) in its largest dimension and no more than 75 millimeters.
Definition: A habitat of rolling or flat terrain where grasses predominate. Typically, what is called a meadow has more biodiversity than a grassland as the former contains not only grasses but a significant variety of annual, biennial and perennial plants.