In geomorphology, a general term for any offshore depositional form, usually running parallel to the coast or across an estuary, and above water at normal tides. A barrier coast is a series of barrier islands, barrier spits, and barrier beaches. Transgressive barriers are those that migrate landwards under the influence of rising sea level and/or a negative sediment budget. Regressive barriers, or strandplains, are large mounds of sediment that have developed along a shoreline with a surface exhibiting well-defined parallel or semi-parallel sand ridges separated by shallow swales. Landwards sediments are deposited on top of more seaward ones. Regressive barriers are linked to a positive sediment budget and/or falling sea level.