**1.2 Research aims and objectives**

coastal dynamic equilibrium for the exchange of materials between land and sea. Consequent upon this, wetlands that function as a medium of water quality improvement, biological productivity and flood risk reduction, always co-exist

*Lagoon Environments Around the World - A Scientific Perspective*

Due to the nearness of lagoons to wetlands and the morphological characteristic that allows for their restricted exchange of water with the adjacent ocean, they are generally vulnerable to organic processes that occur as a direct impact of increasing population densities along the coastline [6, 7]. In addition, coastal lagoons that are considered as one of the most fragile marine environments could likely be altered by global environmental climate change [6]. Such effects may include loss of wetlands due to sea level surface temperature rise, sea level rise, change in hydrodynamics of water masses, alteration in water salinity and increased dissolved oxygen. However, the rise in sea level or global environmental change normally produces a morphological response in the coastal area that drowns many river-valley systems. These, if eventually isolated by longshore current barriers, form lagoons of complex

Coastal lagoons according to Kjerfve and Magill [9] are landforms along the margins of most continents. They are shallow water systems formed in a marginal depression behind barriers [10] and connected to the sea by one or more entrances and with little freshwater influence. Lagoons generally have restricted connections to the ocean [9] compared to their surface area, and hence the water body is poorly flushed. This makes them exhibit long residence times in contrast to a flowing river. The degree of human activities and increased coastal urbanisation, and the impact of natural phenomena (like biological processes, physical processes and erosion, tide and wave propagation) will affect the level of morphological and hydrody-

Lagoons are sensitive areas that play a vital role among the coastal zone ecosystems as they provide suitable breeding areas for many species. In terms of formation, lagoons are formed with their long axes parallel to the coastline [8, 11] where offshore barriers developed more or less parallel to the original shoreline. Nonetheless, the interaction of various coastal processes [12] and increased human action are the major forces controlling the lagoon morphology [13–15] leading to gradual or rapid changes in the landscape of the coastal lagoons. Such morphology can be viewed in two dimensions, lateral or horizontal and vertical or bathymetric.

No coastal lagoon and its immediate catchment area remain static over any timescale (short or long). The natural balance of the coastal lagoon can be seen as the sustainability of the natural ecosystem between the sea and the coastal lagoon. However, no matter how carefully managed the natural balance of the lagoon and its ecosystem, it will be susceptible to change. As a result of the general morphological features, lagoons are naturally very sensitive to dynamic balance in all

The rapidly induced changes in the morphological nature of coastal lagoons due to an incessant increase in population around the coast are prominently brought into display around the Lagos Lagoon, Nigeria (West Africa), the study area in this research. This is the major force that propels this investigation of the morphological and hydrodynamic changes in the Lagos Lagoon. Lagos' population is currently about 17 million, up from 2 to 3 million in the 1970s. Despite this pressure, research to date on the lagoon only identifies ecological studies [17–19], lagoon sensitivity and pollution studies [17, 20, 21], fishery and plankton sustainability [22, 23] and

namic changes that will be experienced in any coastal lagoon.

**1.1 Rationale for the research**

aspects [16].

**80**

parallel with lagoons [5].

outline [8].

The coastlines and the adjacent lagoons of the Nigerian coast have suffered several losses mainly as a result of an inability to manage the sensitive natural balance of the lagoon and its catchment area and retain the initial ecosystem structure and forces that control the natural processes within and around the lagoon's morphological regime. Due to increased urbanisation and industrial expansion witnessed in Lagos from the mid-1970s until the present, the Lagos Lagoon must have been seriously affected, with no remedial action in place.

The existing problem of an overcrowded human population in Lagos, the incessant repository of industrial effluence into its lagoon and increased flooding issues from the immediate watershed has generated two primary research questions for this study. They are as follows:


The aim of this study is to investigate the spatial dynamics of the Lagos Lagoon water floor. In terms of objectives, this chapter analyses the changes on the lagoon water bed resulting from the impact of urbanisation and the changes experienced along its coastline through bathymetric data sets and different statistical tests and analyses on the spatial difference in the lagoon depth characterisation. Moreover, a volume analysis was performed; it enhances the study to calculate erosion and accretion, which was also depicted in map format. Lastly, the significance of the accretion variation with factors that account for uncertainty in the lagoon bottom dynamics is discussed and the chapter ends with concluding remarks and recommendations.
