MORFODINÂMICA DO ?SACO DO LARANJAL?: COSTANOROESTE DO ESTUÁRIO DA LAGUNA DOS PATOS - RS
The objective of the present work is to analyze the morphodynamic characteristics of the ?Saco do Laranjal? an embayment located at the northwest portion of the Patos Lagoon estuary in order to evaluate recent and actual changes associated with the coastal sedimentaryprocesses. The embayment is subdivided in four beaches: Laranjal, Barro Duro, Totó and Colônia de Pescadores Z3. Coastline evolution was based on aerial photographs obtained in 1980 and 1995. Beach profiles surveys and grain size analysis both at the sub aerial and sub aqueous portions of the beach associated were performed at monthly intervals. Additionally a wave forecast model and visual observations were done for specific energetic conditions. Characterization of its morphological evolution, morphodynamic behavior and associated processes will certainly provide important contributions to future plans of coastal management regarding the control and minimization of the erosive processes which occur on a significant portion of the area. Analysis of shoreline changes demonstrate that between 1980 and 1995, erosion rates for Barro Duro beach reached 1.04 m/year. Colônia Z3 beach display some erosional spots and Totó beach presents both erosive and accretional stretches.In contrast, Laranjal beach display accretion and stability. The studies allow to infer that the main erosion causes can be attributed to short period waves generated by local winds, the associated littoral drift and the frequent increase of the water level on the margin during periods of floods associated with winds from the southern quadrant. Significant wave heights and period varied between 0,10 and 0,35 m and 1,2 to 2,9 s, respectively. The five beaches profiles monitored during the study period can be classified as steep mainly due the low breaker height (J 0.25 m) and the coarse characteristics of the beach face sediments. The evaluation of the morphometrics parameters showed high mobility index for Barro Duro Beach, medium for Totó and Colonia Z3 beaches and very low for Laranjal beach. Beachnourishment or the use of a mixed solution (nourishment and groins) is suggested as the more convenient methods to control beach erosion along Barro Duro beach. Sources of goodquality sand were found in the lagoon nearby the erosional sites.
Advisor:Maria Ângela Vaz dos Santos; Antônio Henrique da Fontoura Klein; Paulo Roberto de Freitas Teixeira; Lauro Júlio Calliari
School:Fundação Universidade Federal do Rio Grande
Source Type:Master's Thesis
Keywords:morfodinâmica praial Patos Lagoon estuary estuarine beaches shoreline changes beach morphodynamic nourishment
Date of Publication:04/07/2005