The influence of waves and littoral drift on the eastern gulf clearly shows that the accumulation of sediments along the river spits gave place to formation of new lands that plays an important role in the colonization of mangroves.
In addition, the direction of the littoral drift prevents deltaic sediments of the Atrato River from being distributed along the coasts of the gulf.
Their quays and breakwaters largely block the natural littoral drift and cause rapid accumulation to the south of these harbours and extensive erosion to the north of the latter.
Differently from Estonian beaches that are stabilized by the postglacial land uplift to some extent, these beaches of the central Baltic Proper are mostly maintained by littoral drift of sandy sediment from neighbouring coastal sections.
The littoral drift quantities are higher from May to October, due to heavy breakers associated with the SW monsoon season.
The direction of littoral drift is from south to north during the period of March to October when the waves are between S and SE and from north to south during the period November to February when the wave directions are between E and ENE.
This strategy of construction of permanent, hard engineering structures has successively changed the circulation of sediments by littoral drift and has partially conditioned the type of response from the coastline.
The objective was, according to the local press, to promote beach accretion between two groynes located closely together by the capture of sediments of the littoral drift, in order to stop coastal erosion.
Although littoral drift generally carries sediments to the bayheads, even the healthiest sections of the coast at the bayheads are from time to time subject to erosion.
As typical of the northern coast of Estonia (Orviku & Grano 1992), it has a limited amount of gravel and sand participating in the littoral drift and it develops under sediment deficit.
There is no evidence for volumetrically significant sources of beach grade sediment along the Lake Michigan shore in the study areas other than that moving in the littoral drift and derived, by erosion, from the upland bluffs and dunes.
In the absence of any other proven source for beach-grade sand, the isolation of the back-shore area of a native beach from the on-shore/off-shore interchange of sand and the accretion of littoral drift in and around a shore protection structure ultimately depletes the adjacent shore of beach sand.