Oude Maas
The Oude Maas forms the southern boundary of the IJsselmonde island. Soon after Dordrecht the Dordtsche Kil forks off and after that the Oude Maas forms the northern boundary of the Hoeksche Waard island, flowing west until the Spui river forks off at the town of Oud-Beijerland. The Oude Maas then heads northwest between the towns/cities of Spijkenisse and Hoogvliet and joins the river Nieuwe Maas opposite the city of Vlaardingen. The combined river is known as Het Scheur and flows to the North Sea.