Delta

1. An area of fluvial sediment accumulation that forms at the mouth of some rivers when tides are weak and the accumulation of alluvium exceeds erosion. It is named for its triangular shape, similar to the capital Greek letter "delta" (Δ), which it typically adopts. Among the rivers of the Iberian Peninsula, the best example is the Ebro. 2. The land between the branches of a river at its mouth. A type of river mouth; a dynamic system of shallow channels and alluvial islands found at the mouths of some rivers and generated by the deposition of sediments carried by the water current.