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270D. MUEHE ET ALLItrenches were dug, and one side of the trench wasscraped to obtain compound representative samples.Thirteen sediment samples were obtained from thedune field and its associated deflation plain and afurther 27 samples were collected from the dunebeachsystem. Grain size analysis was made throughdry sieving according the method described by Folk& Ward (1957).The stability of the coastline was assessedby means of a comparison between aerialphotographs from 1970 with orthophotocharts from2000/2002.Climatic data for Arraial do Cabo/Cabo Friowere obtained at following sources: Corpo deBombeiros Militar do Estado do Rio de Janeiro(CBMRJ) for rain, Centro de Previsão do Tempo eEstudos Climáticos (CPTEC) for cold fronts, andRede de Meteorologia do Comando da Aeronáutica(REDEMET) for hourly wind direction and speed.ResultsSediment characterizationSamples collected on the beach (beach faceand berm) and on the top of the foredunes, along thebeach arc, indicate an increase in median grain sizediameter from the southern end toward the center ofthe beach arc, and a decrease towards the northernend. The median grain size is coarsest in the vicinityof the center of the beach arc (P5), and decreasestowards both extremities of the beach. This suggeststhat the region near the center of the beach is adispersal center for the finer sedimentary fractionswhich are displaced preferentially towards the north,possibly being the result of an increase in waveenergy under storm conditions (waves from the SE)due to the more exposed position of this segment.The localized increase in the grain size of the beachsediments is not so clearly reflected in the sedimentsof the foredunes because of the inability of the windto transport sediments greater than 0.2 mm (2.3 phi)(dashed horizontal line in Fig. 4).The finer sands that are more easilytransported by wind are found in the final third ofthe northern extremity of the beach arc (Profile P7),precisely where the beginning of the active dunefield is located.In figure 5 it is presented a correlationbetween the median diameter and the respectivestandard deviation of the sediment samples collectedon the berm, foredune and on the deflation plainwith associated parabolic dunes. The area delineatedon the graph by a broken ellipse indicates the grainsize characteristics of the foredunes whosesediments present a median diameter equal to or lessthan 0.2 mm (2.3 phi) and a standard deviation ofless than 0.7 mm (0.5 phi). The occurrence ofsediments of larger median grain size and higherstandard deviation in the dunes of the deflation plainsuggests the occurrence of residual depositsresulting from the winnowing of the finer fractionsor even a mixture with the sediments of the deflationsurface.Figure 4. Median grain size distribution along the beachand foredune field. The dashed horizontal line representsthe local grain size threshold for eolian sediment transportas depicted in figure 5 indicating a convergence in grainsize between beach and foredune sediments toward thenorthern sector (profile P7) of the beach.Figure 3. Location of the sediment traps (ο), of the topobathymetricprofiles (Pn) and of the beach-foredunesediment samples (Δ). Image Google Earth.Sediment trapsThrough out the monitoring period onlythree traps, 7, 11 and 14, registered a significantcapture of sand. The first two were located on thewindward side of parabolic dunes of the deflationPan-American Journal of Aquatic Sciences (2010) 5(2): 267-276