vallées

Vallées, meaning valleys in French, are elongated, low-lying tracts between hills or mountains. They are among the most common landforms on Earth and host a wide range of ecosystems, human settlements, and transportation routes. The term vallées is used in French-speaking regions to describe river valleys and other low areas shaped by erosion, tectonics, or glaciation.

Valleys form by different processes. Fluvial valleys are carved by rivers through long-term erosion, often producing V-shaped cross-sections. Glacial valleys are shaped by moving ice, typically with a broad U-shaped profile and a flat floor; when glaciers retreat, tributary valleys may remain as hanging valleys. Tectonic or rift valleys form where crustal blocks pull apart, creating long troughs that rivers may later occupy. Local processes such as weathering, sedimentation, and basin subsidence can modify valley shapes over time.

Valley geometry includes the floor or bottom, floodplains, terraces, and the enclosing slopes or sides. Meandering rivers, sediment deposition, and bedrock resistance influence cross-section shape. Valleys create distinct microclimates, moisture regimes, and soil types that support diverse habitats and agriculture. Their vertical and lateral profiles affect drainage patterns, groundwater, and ecological connectivity.

Humans commonly settle valleys due to access to water, fertile soils, and travel corridors. Valleys host villages, farms, and roads, as well as hydropower projects and cultural landscapes. They also pose hazards such as floods, landslides, and erosion, requiring management and land-use planning to balance development with conservation.

Examples include cultural landscapes such as the Loire Valley in France, the Rhine Valley in Central Europe, and the Kathmandu Valley in Nepal, illustrating the interplay between geomorphology and human activity in vallées.