A laguna is seen as a shallow organic structure of H2O which has been separated from the ocean by barrier islands ( sand ) or reefs. Lagoons are normally divided two ( 2 ) , which are, the coastal lagunas and atoll lagunas. Lagoons are either of fresh water organic structures or have some grade of salt with really small or no tidal moving ridges although they might have regular flow of H2O from the ocean. The focal point here is on the coastal lagunas. Kjerfve ( 1994 ) defined a coastal laguna as a shallow H2O organic structure separated from the ocean by a roadblock, linked at least from clip to clip to the ocean by one or more restricted recesss, and normally oriented shore parallel to the ocean.

Coastal lagunas can non be formed along steep or bouldery seashores and are shallow in nature. They are sensitive to alterations in sea degree as a comparative dip in sea degree may go forth a laguna dried out while the rise may destruct the sand barrier. Lagoons are transeunt ecosystems which alterations dimensions and signifier in clip and infinite which is due to a natural procedure. Lagoon has a delicate ecosystem prone to pollution effects from industrial, agricultural and civic runoff.A A


Most coastal lagunas are formed during periods of old sea degree rise. They are developed when the lifting sea invades a comparatively level coastal plane and when a barrier is formed from deposits and sand, it separates the shallow H2O organic structure from the sea. When the sand barrier is attached to tauten land it is called “ lido ” or “ tongue ”


Lagoons are connected to the unfastened oceans by recesss between barriers, the size, figure, vaporization precipitation, and influx of fresh H2O from the recess determines and affects the nature of the laguna. It is with small or no interchange with the ocean or with small floe of fresh water and high vaporization rates may go extremely saline. The laguna accumulates deposits from the shores and tides and as a consequence facilitates the physique up of the laguna.

The features of the laguna is that during low ocean or river flow, the laguna collects deposits and the finer 1s are transported through the mercantile establishment and during flood events the larger deposits are flushed off.

Barrier laguna can be defined as frequently long and narrow offshore sedimentations of sand or deposits that are in correspondence or analogue to the seashore which varies in length and breadth but the focal point here is on the sand barrier coastal laguna. A sand laguna barrier is a long, thin, flaxen stretch of land, oriented analogue to the mainland seashore that protects the seashore from the full force of vigorous or powerful storm moving ridges. Between the sand barrier and the inland is a still, cosseted H2O organic structure. Sand barrier islands are dynamic and vivacious systems, persistently on the move, migrating under the influence of changing storms, sea degrees, moving ridges and tides currents.


It was claimed to hold been formed for over 18,000 old ages ago merely after the terminal of the ice age. As glaciers thaws and recedes, the ocean or sea degree Begin to lift and it flooded the countries behind the ocean at that clip. The lifting H2O moved deposits from the ocean ridges to lodge them in shallow countries along the coastlines. The ocean waves alongside the ocean currents begin to convey in deposits that overtime formed the so called sand barrier for the laguna.

There are three ( 3 ) types of sand coastal lagunas harmonizing to Kjerfve ( 1986 ) which is dependent on the rate and degree of exchange of H2O. See figure below ;

Beginning: Kjerfve, B. ( 1994 )

Choked Lagoons: The Choked lagunas consist of a concatenation of coupled egg-shaped cells, connected by a individual stretched narrow entree channel, along seashores and holding a high moving ridge energy and momentous littoral flow. The entryway channel serves as a vibrant filter which chiefly eliminates tidal currents and water-level fluctuations in the laguna. ( Kjerfve, 1986 ; Kjerfve et al. , 1990 ; Kjerfie and Knoppers, 1991 ) . They are characterized by long blushing times, dominant air current forcing and irregular stratification events due to intense solar radiation or overflows.

Restricted Lagoons: Restricted lagunas consist of a big and broad H2O organic structure, normally shore-parallel, and it exhibits two or more entree channels. As a consequence of this, the restricted coastal lagunas have a chiseled tidal motion which are influenced by the. In restricted Lagoons, the flushing periods are normally non up to that of the clogged coastal lagunas.

Leaky Lagoons: Leaky lagunas are elongated coast-parallel H2O organic structures with many sea entry channels along seashores where tidal currents are satisfactorily strong to flog the inclinations by wave action and littoral impetus to barricade the channel entrances. Leaky lagunas are characterized by a figure tidal moving ridges, unhampered H2O exchange with the ocean on tidal, moving ridge and longer clip graduated tables.


In order for the sand barrier to organize, rather a few conditions must be met. First, there must be a changeless or steady supply of sand to construct the island. This sand may come from the coastal sedimentations or offshore sedimentations ( shoals ) ; in either manner, the sand is as a consequence of the weathering and eroding of stone and was transported to the seashore by rivers in times of heavy flow. The forces of moving ridges, tides and currents must be strong plenty to travel the sand, and out of these three ( 3 ) H2O force per unit area group mechanisms, the dominant force should be the moving ridges.

Several accounts on how sand laguna barrier was developed have been proposed. Harmonizing to one of the theories, coastal sand was transported across the shore as sea degree rose, and one time sea degree stabilized, so the moving ridge and tidal actions worked the sand into a barrier island. a different likeliness is that barrier islands may hold formed from flaxen coastal ridges that became stray from low-lying land and bit by bit formed islands as sea degree rose.

Barrier islands are non inactive in nature ; they are ever altering and are vivacious, with the forces of the moving ridges and air currents continually traveling the barrier island sand. Sea degree alterations besides influence these islands. Barrier islands do non stand entirely ; the whole system of islands develops along favorable shorelines. The constellation of these islands encourages other landforms to construct up and each categorized by their dominant sedimentation type and by the H2O that helps organize them.

Occasionally, during heavy storms, H2O may hotfoot over the island transporting beach and dune sand and lodge the sand in the laguna. This procedure, called peal over, it is indispensable to the being of sand barriers.


Sand barrier islands are characterized by tidal recesss and tidal deltas. Tidal recess is the 1 that allows H2O to travel into and out of lagunas with rise and falling tides. It besides provides a way for high H2O during storms. As the H2O passes in between the recesss, sand is accumulated at the two terminals of the recess ‘s oral cavity, organizing tidal deltas. Finally the deltas fill in with sand and the recess is blocked merely to look someplace else on the sand barrier, usually, at a low topographic point. The size and form of the recess are determined by a assortment of factors, which includes the size of the laguna and the tidal scope. Deep, broad recesss occur where the chief beginning of energy determining the coastal country is tides or tides in concurrence with moving ridges.

PHYSICAL Procedure

While moving ridges and tides can each hold important impacts on coastal semantics, the importance of the two is best understood in combination. In moving ridge dominated countries, the sand barrier are long and narrow because of the rapid migration of tidal recesss in the system, the channel is frequently wiped out as the littorals from the next barriers migrate past. As the tidal scope additions, barrier islands get progressively shorter and tidal-inlet sand organic structures become larger and are positioned perpendicular to coast. In add-on to moving ridges and tides, some other characteristics have influences on coastal development, these are: coastal physical geography, handiness of deposit, river input and tidal prism. Tidal prisms can be an of import factor in developing the morphology of sand barrier island seashore. Barrier recesss are channels that separate one barrier island from another. An recess allows deposits conveyance and H2O motion conveyance between the laguna and unfastened Ocean. The tidal delta littorals are mostly derived from the sea, and it moves inward across the laguna toward the mainland more quickly than outward.

Functions of the sand laguna barrier

They in their nature waiters as a protection of the coastline from storm harm

They serve as place to many species of workss and animate beings

It is portion of the functional ecosystem


The sand laguna barrier has its ain ecosystem. The animate beings and workss that lives in sand barrier laguna parts are such that are able to defy air current and sand scratch, H2O want, salt spray, sand entombment, and invariably switching sand with low H2O retaining capacity. Although these conditions are rough, therefore, limits the coinage assortments that can arise from these environments. Some of the animate beings are the serpent, amphipods, mice and few birds etc.

For nomadic species like fishes and birds, the lagunas systems are linked, because both can easy migrate from one laguna to another through the sea and air, severally. In contrast, smaller size species with more limited scattering, a coastal laguna can stand for an stray environment therefore organizing a closed ecosystem

As identified before, the H2O organic structure of coastal lagunas can be exposed to really strong fluctuations of salts due to seasonal fluctuations of rainfall and vaporization. In add-on, in the shallow environment and the alterations of temperatures are frequently more marked than in the next sea. This may show a hard status for tonss of aquatic species and as a consequence, the biodiversity is atimes lower than what can be found in more reasonably fluctuating coastal environments. Nonetheless, some species have clearly evolved from pelagic species to get by with the laguna ‘s fluctuations through radiative development.

Therefore, while the big fluctuations in lagunas result in lower biodiversity of aquatic beings in the H2O organic structure and its associated deposits, at the landscape degree it becomes a spot different. The lagunas, coastal tongues, their sand barrier and their peripheral wetlands provide ecotones ( passage between two different ecosystems ) which creates highly diversified home grounds that support a high degree of biodiversity

This may be a stressing status for many aquatic species and as a consequence of this ; the biodiversity is most times lower than what can be found in reasonably fluctuating coastal environments. Though, some species have evolved from the aquatic species to get by with the fluctuations of the laguna through radiative development ( Barnes, 1980 ) .


The importance of the sand laguna barrier are legion as they form a natural barrier against air current and moving ridges as they protect inlands from harm as a consequence of heavy storms, they serve as home grounds for workss and animate beings including the endangered 1s.

Lagoons, when in their natural province helps to retain H2O rush from the ocean when there is a rise in the degree of the sea H2O, it collects the overflow H2O, holds it and so deposits it into the other available H2O organic structures. This is a natural procedure which helps in forestalling inundation but when the laguna is non in it natural province or has been blocked or sand filled due to adult males ‘ crackbrained thought like what is go oning in Lagos, it kills this natural procedure of H2O flow and specie protection and as a consequence led to deluging in countries where we should n’t hold been witnessing it.

They can besides be used as diversion countries because it provides a micro clime and has beautiful scenery.

The land barrier plays an of import function in act uponing the form and stableness of the shoreline and filtering suspended affair.

It serves as physical safety from predation and besides serves baby’s room and eating home ground for a assortment of beings

They are habitat for some primary manufacturers

The coastal lagunas are susceptible to disturbance by treading walkers and vehicles can besides pack the sand and crush the flora. This can do the shoreline prone to damage from storm.

The features of a laguna ecosystem

They are typically found along low-lying coastlines that has tides

They are formed and maintained through deposits transit procedure carried by rivers, moving ridges, currents and tides

Water quality of a laguna is influenced by the rate at which the laguna loses or additions H2O either from vaporization, precipitation, groundwater input, surface overflow and exchange with the ocean

Heat is besides gained or lost through exchange with the ambiance

They have low flushing rates and this determines the size and form of the laguna, tidal scope and fresh water flow etc

They are extremely productive ecosystems

They provide habitat for many fishes and shellfish species

Planning AND THE SAND LAGOON BARRIER ECOSYSTEM ( the Lagos state of affairs )

The sand laguna system in Lagos is of such that has witnessed tonss of maltreatments runing from sedimentations of wastes in it to sand filling and digging amongst others. This leads to jeopardizing the species available in the country thereby changing its ecosystem which has long term effects on both the destroyers ( adult male ) and the destroyed as these endangered species may travel nonextant.

The Lagos Lagoon is more than 50 kilometers long and 3 to 13 kilometers broad, separated from the Atlantic Ocean by a long sand tongue 2 to 5 kilometers broad, which has swampy borders on the lagoon side. Its surface country is about 6,354.7 kmA? . [ 1 ] The laguna is reasonably shallow and is non plied by ocean-going ships, but by smaller flatboats and boats.

Disadvantages of Lagoon Systems



aˆ?Large land country required

aˆ?Little control over intervention procedure