Waterschap Hollandse Delta (WSHD) is a Dutch regional water authority covering the south of South Holland with its seat in Ridderkerk. The area it encompasses includes Rotterdam as well as the (former) islands Goeree-Overflakkee, Hoeksche Waard, Voorne-Putten, the Island of Dordrecht, IJsselmonde, Rozenburg and Tiengemeten.