The determination of priority areas at risk for contaminant mobility challenges scientists and resource managers, who are increasingly prevailed upon to provide a predictive understanding of the processes and relative dangers associated with the degrading of the aquatic environment. Comprehensive and joint applications of GIS and statistics approach were applied in identification and spatial patterns of coastal water pollution sources with a large data set obtained through coastal water monitoring of Oualidia lagoon. This chapter describes environmental statute, discusses its ecological and socio-economic impacts and provides a GIS analysis for heavy metal assessment of sediments in coastal lagoon. The aim is to establish spatial correlations and between clays sediment distributions and total heavy metal concentrations. Further, it determines whether observed anomaly is due to natural geology (sediment grain size) or is affected by discharge from anthropogenic sources. Spatial distribution modelling of heavy metal concentrations are produced to indicate contamination plumes from possible anthropogenic sources and to reveal potential hot spots and dispersion patterns. A direct correlation between clay-enriched and high concentration of aluminium is detected, however regions of high concentrations of heavy metal indicate a relationship to anthropogenic sources.