istributed 
‘ognition, 
90. Neu- 
ich. 
ral Com- 
REMOTE SENSING MONITORING OF ESTUARINE 
WATER FLUXES THROUGH A TIDAL INLET 
Jarbas Bonetti Filho 
Oceanographic Institute 
University of Säo Paulo, Brazil 
e-mail: bonetti@usp.br 
Commission VII, Working Group 8 
KEY WORDS: Coast, Landsat, Digital Image Processing, Water Quality Monitoring 
ABSTRACT: 
The practical application of Remote Sensing technologies in water quality monitoring has been increasingly 
attempted in the last few years. This paper presents an experiment on LANDSAT-5 digital image processing, 
applied to a time series, in estuarine water fluxes monitoring. 
The chosen targets were the waters near Barra de Cananéia, a Brazilian tidal inlet located near to the Tropic of 
Capricorn. The main sources of dissolved and suspended materials are located at a 2.500 Km? coastal plain of the 
inner lagoonal-estuarine system. The associated vegetation is composed by mangroves and rain forests and are 
responsible for the input of dissolved organic matter (yellow substance) in the waters. Particulate suspended 
sediments in the column are essentially related to sandy terrace's erosion and to bottom sediment's resuspension. 
Three LANDSAT-5 images were used in the study. They were co-registered and digitally processed in a computer 
system, following the steps: histogram's analysis; atmospheric correction; digital numbers surveying and 
densitometric transects; water/land separation; linear contrast enhancement; pseudo-color and color composition. 
Brightness temperatures were also obtained and quantified from TM. 6. 
The results clearly demonstrated time dependent variations in estuarine front's shape, dimension and spectral 
response. The April 1984 image indicated the predominance of inorganic suspended sediments in surface waters 
and the September 1986 image presented a large input of yellow substance from the lagoonal-estuarine system. A 
possible seasonal control is suggested to explain these variations. 
1. INTRODUCTION 
The aim of the present work is to contribute to the 
1.1 Motivation comprehension of these fluxes. For this, a sequence of 
digital image processing steps were applied on a 
Despite the increasing number of research works on LANDSAT-5/TM time series. The test targets were 
estuarine water fluxes, the comprehension of suspended ^ the waters close to a Brazilian tidal inlet called Barra de 
and dissolved matter transport in such systems is still ^ Cananéia, the main mouth of a well-preserved 
weak. A good approach for its improvement is to focus lagoonal-estuarine system, located near to the Tropic of 
the sampling areas near to tidal inlets, which seem to Capricorn. 
be the best places for the monitoring of inner waters' 
dispersion, since they represent the point of contact — 1.2 Study Area 
between oceanic and estuarine volumes. Nevertheless, 
the adversity for data collecting grows near these ^ Cananéia-Iguape Lagoonal-Estuarine System is located 
features, since navigation (and traditional data at the southern coast of Säo Paulo State, being 
sampling by vessels) is often harmed by sea conditions. composed by several connected water bodies that were 
developed inside a 2.500 Km? Quaternary sandy coastal 
The possibility to evaluate the enrichment of coastal plain. It covers a 100 Km coastline and the inner 
waters and the paths of introduced waste disposals ^ waters are connected to the sea by three tidal inlets. 
justifies the development of practical methodologies for ^ Barra de Cananéia is the most important of them and 
estuarine fronts monitoring. Many authors have exhibits the higher water exchange rates. A well 
already demonstrated that the use of Remote Sensing developed ebb tidal delta also occurs at this point, 
in such investigations is highly satisfactory (Froidefond leading to great depth variations, with a maximum 
et al., 1991; Nichol, 1993), since well-developed optical ^ close to 22,0 m in its main circulation channel. The 
fronts are frequently associated to these areas. width of the inlet varies between 1.200 m and 1.500 m. 
77 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996