||Mont Saint-Michel was previously connected to the mainland via a thin natural land bridge, which before modernization was covered at high tide and revealed at low tide. This connection has been compromised by several developments. Over the centuries, the coastal flats have been polderised to create pasture. Thus the distance between the shore and the south coast of Mont-Saint-Michel has decreased. The Couesnon River has been canalised, reducing the flow of water and thereby encouraging a silting-up of the bay. In 1879, the land bridge was fortified into a true causeway. This prevented the tide from scouring the silt around the mount.