Estuaries occur where coastal rivers enter the sea, creating a mix of fresh and saltwater habitats. These habitats change with each tide. During flood tide, ocean water pulses into the estuary and up the lower reaches of the river. At ebb, fresh water pours into the estuary basin, pushing a wedge of lighter fresh water and riverborne sediments into the estuary. Why is an estuary important? Protected inner waters of estuaries, laden with sediment, form the richest of coastal environments. Their productivity far exceeds that of either the finest agricultural land or the open ocean. 80% of the Fraser Estuary has been lost, altered/developed. 50% of the Squamish estuary has been lost, altered/developed. Estuaries are a scarce resource, less than 3% of BC's coastline.