The 630-km long coastline of Rio Grande do Sul, the southernmost state in Brazil, wasrnfrequently described as a very homogeneous and straight, exposed sandy beach. Only recentlyrnstudies have pointed that this coast is not straight and shows local and regional morphodynamicrndifferences. From 1997 to 2000, the Rio Grande do Sul shoreline was mapped annually using thernkinematic Global Positioning System (GPS) method. In 1997, 1998, and 1999, shorelines werernmapped in November (end of spring), allowing evaluation of changes that have happened under thernsame energetic conditions. The 2000 shoreline was monitored in June, allowing assessment of thernseasonal shoreline changes. Alongshore distance vs. Shoreline change graphs were used to determinernpatterns of changes in the Rio Grande do Sul shore. Differences occur in the annual and totalrnmaximum amplitude of shoreline displacement, in the patterns of alongshore changes, and in therneffects of seasonality. In general terms, the 1999-1998 and 1998-1997 lines behave similarly in thernsouthern sector, and oscillate in opposite directions along the central and northern sectors,rnsuggesting a rhythmic shoreline configuration. A nearly perfect mirror image between the linesrn1999-1998 and 2000-1999 observed along the northern part of the southern sector indicates a beachrnrecover in a seasonal time scale. Similar effect is observed along the northern sector in a longer timernscale (19 months). The kinematic GPS turned to be a reliable, fast, and economic method to obtainrnaccurate shoreline position data along the Rio Grande do Sul coast.
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