The results are presented of research conducted in the area of Porto Piscinas in SW Sardinia, characterized by a transitional coastal system (watercourses, river mouths, beaches, sand dunes) in a Mediterranean environment. The investigation involved direct surveys photointerpretation and a series of sedimentological, morphoscopic and SEM observations on samples coming from the different facies of the system. The study aimed not only at determining the geoenvironmental characteristics and the dynamics of the system but also at gaining an insigth into the effects produced by the interaction of morphogenetic, fluvial, littoral, eolian and anthropic processes. In this transition system textural, mineralogical, morphoscopic and chromatic variations have been observed in the sediments collected in the different subenvironments, attributable to their respective genetic and evolutionary processes. The investigations have shown that the sediments transported by the rivers contribute to the system’s equilibrium and are contaminated by the material eroding from the huge mine waste and tailings dumps in the now abandoned Montevecchio and Ingurtosu mining districts. The toxicity of these deposits is responsible for the large abiotic stretches in the gravel beds of the rivers Piscinas and Naracauli, which are dry for most of the year. A comparative examination of different series of aerial photographs from 1954 onwards, revealed that the dunes are migrating landward at the rate of a few metres a year.