PROCEDURES TO THE MAPPING OF THE COASTAL FEATURES
ISBN 978-85-88783-11-9
Authors
1da Silva, A.; 2Alencar Castro, J.W.; 3Ferreira Dias, F.; 4Osilieri, P.
1SANTA ÚRSULA UNIVERSITY / BRAZILIAN NAVY Email: prof_agenor@hotmail.com
2MUSEU NACIONAL DO RIO DE JANEIRO – UFRJ Email: jwacastro@gmail.com
3UNIVERSIDADE FEDERAL FLUMINENSE - UFF Email: fabiofgeo@yahoo.com.br
4MUSEU NACIONAL DO RIO DE JANEIRO - UFRJ Email: osilieri.paulo@yahoo.com.br
Abstract
This work highlights very specific and important aspects of mapping to the nautical cartography due of the changes of the position on coastline contour. The coastline contours is the major concern of this work. Shoreline changes due the erosion or accretion are natural processes that take place over a range of time scales. They may occur to the smaller-scale (short-term) due storms, wave action, tides and winds, or in response to large-scale (long-term) events that may alter the actual position of the line of the shoreline. Some times the dynamics of sedimentation on the outlines can result at an imprecise nautical chart. The present work aims to granulometric studies of the sediments from the coastal areas of the Rio de Janeiro city where the depositional dynamics affects the cartographic accuracy of the nautical charts. The sedimentation processes almost always changes the position of a shoreline on time. Specific mapping procedures must be used to map the limits between the sea and the continents when intense erosive processes occur in a region. The case presented here concerns to strips sand stability of the Leblon beach segment - Arpoador, including the Ipanema beach and the frontal beach to the Jardim de Allah channel. The samples of beach sediment were obtained by stainless-steel catcher was the main data used in this work. Data of winds, waves and currents are used to determine how the sedimentation processes affect the evolution of the coastal boundary. Historical satellite images and field seasonal surveys to collect of beach sediments are part of the procedures for determine the depositional processes in the coastal strip. The results here are from the study of depositional dynamics on the coastal Brazilian to the Ipanema beach in the Rio de Janeiro city. In Cartographic sense this concern to the coast line position and is showed to the strip sand in dimension of the beaches since Arpoador and Ipanema until the Leblon beach since the year of 2000. Environmental data, granulometry data of the beach profiles and historical satellite images were main data used together to show the close relationship between the sedimentation processes and sand strip variations on these beaches in Rio de Janeiro city – Brazil. The narrower range of sand in Leblon almost always corresponds to a greater range of sand on the beach of Ipanema. Along coastline the slope varies few degrees. The profile is more sloped in Leblon beach where in some times the erosion process is more intensive. During this study large quantities of sand were moved from Arpoador beach to the Leblon beach. In this study were analyzed 18 sediment samples from 6 profiles along the beaches. The grain size analysis showed that the sand grains become segregated as they main move along the beach from east to west, becoming increasingly finest when transported from Arpoador beach to the Ipanema beach. The Leblon beach has coarse grains. However the medium sands grained are predominant in the rest of this coast. On most of these beaches the grains are moderately well sorted, due mainly to the action of coastal currents, waves, and tides. The results show how dimension in the size of beaches has occurred. Next to the Jardim Allah channel at begin of Leblon beach different depositional mechanics of sediments are registered in relation to the Arpoador beach. When the Leblon beach have little dimension the beach strip at Arpoador beach is larger. So, the grain size variation can explain changes in rate migration of the line coast. Due to varying of the depositional coastal processes every beach has different positions to the boundary of shoreline at different times of the year. Cartographic works have recognized recently the need by improve the knowledge of coastal sedimentation processes to improve the accuracy of shoreline mapping.
Keywords
Sedimentation processes; dynamics shoreline; Ipanema beach