 The longshore drift of sediment can be considered both a source and a sink due to the fact that in some case it can add sediment to a coastline but in others transport sediment away from a coastline.An example of both extremes of longshore drift can be found on the Canterbury coastline in New Zealand, either side of Banks Peninsular.Both the Waimakariri River in the north and the Canterbury Bight in the south of the Banks Peninsula provide large amounts of sediment respectively.