The Site, at the confluence of the Rhine and Meuse rivers, is formed by tidal freshwater floodplain marshes characterized by reedbeds, swamp forests and creeks. Biesbosch was created in the year 1421 during the Sint Elizabeth flood, which created an inland sea of 30,000 hectares under the influence of river waters and the tide. The original Site was extended significantly to align with the Natura 2000 boundary, resulting in the addition of an area of over 6,800 hectares. Biesbosch is rich in biodiversity and supports globally threatened species of birds such as common pochard (Aythya ferina) and horned grebe (Podiceps auritus). It also regularly supports more than 20,000 wintering waterbirds and more than 1% of the populations of six different species of ducks. The shallow waters provide a spawning, nursery and feeding grounds for various fish and mollusc species. The Site’s hydrological values include flood control, sediment and nutrient retention, and water purification. It is also used for farming and reed cutting, and it hosts wind farms and commercial fisheries. Threats to the ecological character of the Site include pollution and impacts of recreational activities. There is a visitors’ centre, and biodiversity monitoring activities are carried out by the Dutch Bird Research Organisation.