The Valley of Anastomosing Narew River (NE Poland)—A Unique Fluvial Landscape of the European Lowlands

There are three basic types of rivers in the world. Apart from the frequent meandering and braided rivers, the anastomosing river type is one of the rarest. The valley of the anastomosing upper Narew River (NE Poland) is natural and therefore unique in Europe. The anastomosing river is a multi-channel river system of very low energy. The channels are relatively narrow and deep. The floodplainFloodplain is built from sediments resistant to erosion and therefore the fluvialFluvial system is stable, with little change over hundreds of years. The floodplain is often submerged, and hence, it is an environment of dense aquatic vegetation. It is still unclear why this river reach obtained a specific anastomosing pattern. The article presents various hypotheses on this topic. The geological history of the Narew valley and its vicinity during the last million years is also presented. The river changed its character several times, in relation to climatic fluctuations occurring in the Pleistocene and Holocene. Other examples of Polish rivers with features of anastomosing pattern are also given, and a fluvial analogue of the Narew River in southern Africa has been found.