The vlei, under natural conditions, would dry out completely at certain times of the year. Zandvlei is, however a semi-estuarine system as a result of changes to its catchment and the mouth. The water level in the estuary is controlled by a rubble weir and a sand bar , which is opened periodically.
The Zandvlei Estuary drains into the northern point of False Bay with its mouth adjacent to the popular Muizenberg Beach. Zandvlei is the only functioning estuary on Cape Town’s False Bay coast.
The estuary was neglected in the past and was negatively affected by farming, urban development, dredging and the introduction of alien invasive species. The original vegetation has been partly restored through local government initiatives and the efforts of volunteers.
The Zandvlei Estuary is rated within the top 25% (as far its importance is concerned) of all the estuaries along the South African coastline.