Morphodynamics in a Tropical Shallow Lagoon: Observation and Inferences of Change

Lagoon system and its adjacent tidal basins exhibit dynamics which are significantly different on both spatial and temporal scales. This is expected from a semi-diurnal tidal regime; as urbanization and human activities around the lagoon increases, and the volume of sediment that is entering into the basin is believed to be increasing on a daily basis. The changes on the Lagos Lagoon water bed over six years' time scale using repeated bathymetric data (2008 and 2014) was presented in this chapter. In overview, it presents a basic understanding of bathymetry as a process of acquiring the bathymetric data that was used in the research. The procedure of the bathymetry and data reduction is followed by analysis of the Lagoon water bed dynamics using abstracted profile lines from the bathymetric data in a GIS environment (ArcGIS 10.1). However, the results of the significant accretion and erosion inside the Lagoon were analyzed spatially to quantify the volume of sediment gain or loss on the Lagoon water floor. Part of the findings shows that between 6 years, average height of 0.16m was gained by the Lagoon. Going by this rate it means that in 1 year the height of accretion will be 0.026m. This enhanced the possibility of verifying if the Lagoon is disappearing gradually. To the best of the author's knowledge, this research among the various researches that has been done on the Lagoon reveals for the first time the various kinds of evolutionary changes (channel movement, accretion, erosion, infill and movement of shoal) on the Lagoon water bed.