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274D. MUEHE ET ALLIFigure 15. Estimated erosive adjustment of differentsectors of the coastline to distinct sea level rise scenariosaccording to the Bruun rule. Profile locations in figure 3.Figure 13. Overlay of the 12 monthly topographicprofiles of the foredune-beach system indicating theabsence of net erosion during the period of observation.The last profile is represented by a red line. Location ofprofiles in figure 3.Figure 14. Topo-bathymetric profiles of the foredunebeach-shorefacesystem compared to the equilibriumprofile (broken line) according to the model proposed byDean (1991).The non-identification of an erosive trend ofthe coastline (not taking into account the possiblelack of sediments in the middle shoreface) isauspicious in the sense that it indicates a certainrobustness of the coast in the face of the variabilityof the coastal processes.However, a rise in sea-level will tend toresult in an erosive adaptation of the coastline asthere are no sediment sources to compensate for thisrise. The application of Bruun´s model (1962, 1988),as described above, to provide a rough estimate ofthe amplitude of this response to different scenariosof sea level rise, is presented in figure 15; the modelpredicts an increase in the amplitude of the retreatfrom the center to the extremities of the beach arc aresult that stems essentially from the lower gradientof the shoreface, associated with a smaller grain sizein the northern and southern sectors of Peró beach.For the urban area, behind profile P2, thiserosive adaptation will mean the destruction of thepublic walk in front of the urban area, unless thebeach is preserved by means of artificial landfill.Another vulnerability factor arises from the shallowdepth of the water table and the poor drainage of thedeflation plain with the consequent renewedflooding of the low-lying areas that were extensivelyflooded during a period of intense rainfall thatoccurred in the period from January to May 2008.ConclusionThe Peró coastal plain, with its system ofsandy dunes, presents a highly sensitive environmentalequilibrium, as climatic oscillations tendingto drier weather, independently of global changes,can disturb its delicate morpho-sedimentary balance.Alterations in the water balance, whether by dimini-Pan-American Journal of Aquatic Sciences (2010) 5(2): 267-276