Miguel da Guia Albuquerque

Erosion or Coastal Variability: An Evaluation of the DSAS and the Change Polygon Methods for the Determination of Erosive Processes on Sandy Beaches

ABSTRACT Albuquerque, M., Espinoza, J., Teixeira, P., de Oliveira, A., Corrêa, I., Calliari, L., 2013. Erosion or Coastal Variability: an evaluation of the DSAS and the Change Polygon methods for the determination of erosive processes on sandy beaches. There has recently been growing concern about issues related to erosive processes on sandy beaches and climate change in the scientific community. Several methodologies have been proposed in the worldwide literature to quantify coastline retreat on shorelines in an accurate way. It has been questioned whether these methodologies show the erosive process or the shoreline variability in a certain area. From this perspective, this paper aims at characterizing the accuracy of the Digital Shoreline Analysis System (DSAS) and the Change Polygon Method in the studies of regression on shorelines which are prone to erosion. Data collected by a GPS-RTK along Hermenegildo Beach, located in the south of Brazil, and the geo-referencing of satellite images enabled the outline of the shoreline in different periods with the use of both methodologies and the analysis of their accuracy. The DSAS showed good correlation among data; however, since it uses equidistant transects, it could not account for some features in the shape of crests or troughs in the area under study. The DSAS is based on the calculation of rates of statistical variations in a series of vector data that represents the shoreline. In order to correct those features that were not accounted for by the transects, more lines would have to be created so that a larger stretch of the area under study could be reached. The Change Polygon Method, based on the creation of polygons with lines from different periods, may be used to calculate the area of the region under study and compare it with areas from other periods. The calculated shoreline length led to the definition of the shoreline displacement in meters per year. The correlation was 13% (R2=0.131) in terms of reliability for the DSAS whereas it was 94% (R2=0.9418) for the Change Polygon Method, considering the same shorelines. Results showed that the Change Polygon Method is more reliable to evaluate variations in areas and shorelines by comparison with the DSAS. Choosing an efficient method to identify problematic areas with economic and social risks is fundamental to define strategies for proper management of places with erosive processes.

Levantamento do nível do lençol freático da área urbana dos bairros Querência e Atlântico Sul, Balneário Cassino - RS, a partir de dados de georadar

Esse estudo visa caracterizar o comportamento do lencol freatico na area urbana do balneario Cassino, Rio Grande do Sul, nos bairros Querencia e Atlântico Sul. A partir de dados de altimetria do terreno (obtidos com GNSS-RTK), composicao do solo, pluviosidade, GPR ( Ground Penetration Radar ) e medicao da profundidade do lencol freatico foram possiveis medir as diferentes profundidades da franja capilar superior e inferior do lencol freatico e estimar as zonas com maior suscetibilidade a alagamentos. As posicoes de nivel do lencol freatico superficial obtido com GPR corroboraram com os valores medidos in situ atraves da escavacao de pocos de observacao com uso de trado manual. O lencol freatico apresentou um carater superficial, com valor medio de 0,59 m de profundidade e aeracao pouco espessa. Para o lencol freatico profundo, o nivel medio estimado foi de 1,37 m. Atraves da modelagem foi possivel observar que o solo apresenta um maior indice de vazios nas regioes onde o lencol freatico e mais profundo. Nas localidades onde o solo apresenta uma menor capacidade de absorcao da agua da chuva ha uma maior suscetibilidade a alagamentos. A saturacao do solo, como consequencia o alagamento de uma regiao, ocorre quando o aporte de agua corresponde ao volume livre do solo, que no caso da area de estudo, apresentou limiar de saturacao na ordem de 108,78 mm. O conhecimento do comportamento do lencol freatico e fundamental para que os gestores municipais disponham de ferramentas para o devido planejamento das localidades suscetiveis a alagamentos no balneario Cassino.

Use of the remote sensing to obtained the dispersing of the traces pollutants concentration: Preliminary results to the city of Rio Grande, Southern Brazil

This paper aims characterized in the quantification of the air pollutants from fertilizer industry, in Rio Grande, south of Brazil. From samples collected in situ, radiometric data and hyperspectral imaging was possible quantify the regions which showed the largest precipitation of pollutants from the production of fertilizers. For soil samples, the values of sulfate, these results comprise a range 0.004-0.077 mEq. The lowest concentrations were cataloged NW of Rio Grande and in some localities the SW of the city industrial district. To the nitrate concentration, the highest percentages were cataloged in most of the urbanized area. The range of nitrate concentration was approximately 0.010-0.092 mEq. The concentrations of nitrates and sulfates, obtained by hyperion images showed maximum values of 0.092mEq and 0.338 mEq, respectively. Both samples showed a correlation of 76% with respect to pollutant concentration.

Use of remote sensing images to determination of the values shoreline retraction, in periods of El Niño in the South of Brazil

This paper aims to characterize the established erosion process at Hermenegildo beach, southern Brazil, during the period of 1947 to 2007. From data collected in the field with RTK-GPS, aerial photographs, satellite images associated with database of sea surface temperature and El Niño was possible to establish the rates of decline of shoreline for a period of 60 years. The results demonstrate that the Hermenegildo beach is under severe erosion process. In periods subsequent to the occurrence of El Niño and thermal anomalies it can be observed the highest shoreline recession rates and hence the greatest losses of homes near the coastline, due to severe erosion process.

Use of technicals of remote sensing for the development of digital elevation model from video images

The objective of this study is to characterize the process of extracting digital elevation models from ARGUS video images and remote sensing techniques. Using principal components analysis, the record of images into a UTM coordinate system, together with the acquisition of image parameters it was possible to extract altimetry from a 2D image to generate a 3D image. The use of data collected on site and the use of polynomial linear regression models it was possible to calibrate the 3D images in a way to better represent altimetry with great accuracy. In this context, the video monitoring system with 3D view turns out to be an important low cost tool to monitor coastal environments, allowing the analysis of vertical changes and thus permitting a better understanding of beach morphodynamics for the coastal managers.