Journal of Coastal Research SI 39 1618 - 1621 ICS 2004 (Proceedings) Brazil ISSN 0749-0208
SOUTO, M. V. S.; CASTRO, A. F.; GRIGIO, A. M.; AMARO, V.E. and VITAL, H., 2005. Multitemporal analysis of geoenvironmental elements of the coastal dynamics of the region of the Ponta do Tubarão, City of Macau/RN, on the basis of remote sensing products and integration in GIS. Journal of Coastal Research, SI 39 (Proccendigs of the 8th International Coastal Symposium), 1618 - 1621. Itajaí, SC, Brazil, ISSN 0749-0208.
The study area is inserted on the region of Macau in the northern coast of the Rio Grande do Norte State, composed of tertiary and quaternary sediments. This region is characterized by the intense action of coastal processes, causing the morphologic instability in the area beyond the interference of human activities, petroliferous industry, salt companies and the expansion of shrimp farms. This situation justifies the integration of scientific multidisciplinary and multitemporal studies to the evaluation of the changing behavior of this coastal environment. This study of environmental characterization is a basic tool to the identification of areas for protection and recovery, mainly those that suffer huge social-economic intervention. The main goal of this paper is the geoenvironmental monitoring by the analysis of multitemporal images (from years 1989, 2000 and 2001) of georeferencing orbital sensors, from the topographic maps (SUDENE SB-24-X-D-II Macau and SB-24-X-D-III São Bento do Norte, both with 1:100.000 scale) and photos from low altitude aerial surveys. These sensors products had been analyzed by through digital image processing techniques to produce index maps (land use, geology, geomorphology and soil) and environmental vulnerability to the social-economic occupation, aiming to determine sensitive and/or damaged areas. The thematic maps had been produced on 1:50.000 scale and stored in georeferencing database composed in a GIS, being used as source of consultations in a decision making to the environmental sustainable of the region and on Oil-Spill Environmental Sensitivity Maps of the Coast Areas. The application of these techniques in the area allowed the optimization and/or implantation of social-economic activities causing low environmental impact, avoiding environmental protected areas and benefiting the investors with better productivity and security in areas selection.
ADDITIONAL INDEX WORDS:Remote sensing, geoenvironmental monitoring, multitemporal analysis.
ABSTRACT
Multitemporal Analysis of Geoenvironmental Elements of the Coastal Dynamics of the Region of the Ponta do Tubarão, City of Macau/RN, on the Basis of Remote Sensing Products and Integration in GIS
M. V. S. Souto†; A. F. Castro†; A. M. Grigio†; V. E. Amaro‡ and H. Vital‡
INTRODUCTION
The Ponta do Tubarão region, nearby Macau city on the northern coast of Rio Grande do Norte State, is characterized for being submitted to continuous transport processes of the seaboard and aeolian sediment, causing a morphologic instability to a large extention of the area. Moreover, one can stand out the interference of human activities such as the Guamaré Petroliferous Industrial Pole, salt companies and shrimp farms expansion that represent most of the economic activities of the State.
Recent papers have demonstrated geoprocessing techniques application mainly used in the evaluation of coastal environment dynamics and its multitemporal (annual and/or decenies) variations, based on digital image processing of orbital and airborne remote sensors products ( 1996;
1999; 2000; 2001;
2002; 2002; 2002;
and 2002; 2002).
Thus, the geoenvironmental elements changes monitoring based on multitemporal analysis of geocoding remote sensing images allowed the comparison of three distinct dates (years of 1989, 2000, and 2001) on the diagnosis and semiquantification of susceptible and/or damaged areas caused by human activities in the region, beyond decurrent changes due to natural processes.
SINGHROY, BARBOSA SOUZAFILHO, SOUTO
AMARO ALVES LIMA
SOUTO AMARO, SOUTO,
et al., et al.,
et al., et al., et al.,
METHODS
The applied methodology was based on comparison between Landsat multispectral imagens of three distinct dates (two
Landsat 5-TM WRS-215064 from August/02/1989 and June/13/2000, and one Landsat 7-ETM+ WRS-215064 from April/05/2001), georeferenced on Datum SAD-69 and UTM- S24 cartographic projection (Root Mean Square less than 0,20) from the SUDENE topographic maps: Macau-SB-24-X-D-II and São Bento do Norte-SB-24-X-D-III, both in 1:100.000 scale, and supplementary GPS data collection.
These multispectral images were submmited to digital image processing for radiometric enhancement and delimitation of different landscape units recognized in the area. Such techniques correspond to multiband function treatments based on the algorithms of software ER-Mapper Version 6.3 (Earth Resource Mapping).
The applied techniques were mainly colour composites preparation in the RGB system ( ed; reen; lue), bands ratio and indexes methods (NDVI - Normalized Difference Vegetation Index). These distinct techniques allowed the analysis and classification of the orbital images spectral data.
Each spectral band was contrast enhanced by hystogram stretching functions to highlight the borders between the surface units.
Afterwards these processed images were conducted to Geographic Information System environment ArcView software v. Version 3.2 (ESRI) which allowed the diverse thematic maps (Land Use, Geomorphology, Geology, Soil and Environmental Vulnerability) preparation on a 1:50.000 scale.
These database were stored in GIS as a geocoded basis available for consultations and decisions making for environmental index maps applied to the sustainable development of this coastal zone.
R G B
†Programa de Pós-Graduação em Geodinâmica e Geofísica. Universidade Federal do Rio Grande do Norte. Campus Universitário, P.O.Box 1596, 59072-970, Natal-RN, Brazil. PRH22-ANP.
michaels_br@yahoo.com.br;
angelica@summer.com.br;
grigioma@yahoo.com
‡ Programa de Pós-Graduação em Geodinâmica e Geofísica. Departamento de Geologia. Universidade Federal do Rio Grande do Norte. Campus Universitário, P.O.Box 1596, 59072-970, Natal-RN, Brazil. PRH22-ANP. CNPq Researcher.
amaro@geologia.ufrn.br;
Journal of Coastal Research Special Issue 39, 2006,
RESULTS
The obtained results allowed the execution of comparative thematic maps (Land Use, Geomorphology, Geology, and Soil) for three distinct dates, that assisted the preparation of the Environmental Vulnerability Map (Figure 2). The multitemporal comparison took account of areal changes of geoenvironmental elements distribution.
The Environmental Vulnerability Map was prepared in accordance with the techniques developed during the preparation of the “Ecological-Economic Zoning of the Rio Grande do Norte State Estuaries and its Surroundings”
2002). The vulnerability levels established for the geoenvironmental units present on the estuaries reflect the geologic-geomorphologics compartment fragility conditions.
In this study, the vulnerability levels was defined on the basis of the geomorphologic stability and geologic characteristics (morphogenesis-pedogenesis aspects, 1977, 2002) of the landscape units. When integrated to the
aspects of land use, economic occupation and human interventions on the coastal zone they supply an evaluation of the risk on each geoenvironmental unit. Futhermore it must be considered the aspects of social-economic development of the region and the perspectives of enterprises installation with negative impact to ecosystems ( 2002). Therefore, the proposal methodology used the geologic-geomorphologics compartments as a basis for the definition of the geoenvironmental units, allowing their relationship analysis and their integration with the physical and biological aspects.
The environmental vulnerability level measures the fragility of the geoenvironmental units to the damage impact agents. As environmental impact definition “positive or negative changes in the conditions of health and welfare of the people and in the stability of the ecosystem, on which depends the survival human being; such actions can accidental or be planned provoking direct or indirect alterations” ( 1985). The recognition of the natural systems vulnerability is a basic approach in the forecast of the environment dynamic behavior and the occupation process of the coastal territory. One becomes, therefore, basis for the ecological-economic zoning maps preparation.
The sellected parameters allowed the definition of three vulnerability indexes (High, Medium and Low) applied to described geoenvironmental units, based on the proposal of
and (1978), and (1993)
and (2002). For the study area 6 (six) geoenvironmental units were established and presented in Table 1: Unit I Tidal Plain; Unit II - Mangroves; Unit III River Estuarine Flooding; Unit IV - Mobile Dunes/Interdune; Unit V Fixed Dunes/Interdune; Unit VI - Planing Surface.
Another important result was the detection of gradual replacement of salt tanks by shrimp farms, evident on land use maps comparison (years of 1989, 2000, and 2001), accompaining the increase of this social-economic activity on State of the Rio Grande do Norte government policy. This changes were showed on the areas of Melancia and Sertãozinho Salt Farm, and the expansion of the shrimp tanks in other areas.
Also Cristal Salt Farm recently constructed few shrimp tanks nearby a petroliferous extraction field ( 2002).
(GEOPRO,
TRICART, GEOPRO,
SOUTO,
PARKER,
GUNDLACH HAYES MICHEL DAHLIM
SILVEIRA
SOUTO, Figure 1. Location of the study area, the region of the Ponta do
Tubarão, located in the City of Macau, northern portion of the State of the Rio Grande do Norte (Brazil).
BRAZIL Lajes
38°
Açu Apodi
BR-304 BR-405
Mossoró
BR-406 37°
NATAL 36°
5°
6°
Galinhos Macau Tibau
G State Capital
City Roaway Area
LEGEND
0 25 50km
Graphic Scale
A T L A N T I C
O C E AN
Figure 2. Environmental Vulnerability Map of 04/05/2001.
Multitemporal Analysis
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ANALYSIS
On the basis of thematic map integration were identified six geoenvironmental units based on radiometric signatures of the surface and checked by field information. Such recognized units were classified by Landsat images combinations as: RGB 7/1-5/1-4/1, RGB 7/3-5/3-4/3, RGB 7/4-5/3-4/2, RGB 7-5-3, and RGB 5-3-1, that assisted the detection and delimitation of these units through the spectral properties of each one of them (Table 2).
The land use maps revealed efficiency on the recognition of changes occured on the surface due to both natural and human intervention in time intervals of long period (about of 11 years) and short period (approximately 1 year).
The first time interval (in between years 1989-2000) detached huge changes occured on the shoreline caused by natural coastal processes, which characterizes the intense coastal dynamics on this region. Also the natural southwestward movement of mobile dunes forming corridors had been verified and the dune field accumulation. During the time interval (years 2000-2001) the changes due to human activities are more distinguished, representing the expansion of the economic activities of shrimp farms in the region, marked by prominent constructions and enlargements of tanks, beyond the substitution of the salt crystalization/evaporation tanks. The coastal changes were well defined, mainly due to intense erosive processes operating in the region for these two time intervals.
Owing to these modifications analyzed on multitemporal maps of land use (for the years 1989, 2000 and 2001) associated to the thematic maps of Soil, Geology and Geomorphology, the interpolation itself generated three indexes of environmental vulnerability (Low, Medium, and High), applied to the six recognized geoenvironmental units for the study area. The units with High Vulnerability correspond to the mangroves area (protection area) and the areas that involve shoreline zones (foreshore plus backshore) due to intense morphodynamic action (Table 1). The units of Medium Vulnerability are the areas related with tidal/estuarine plains, fixed plains of river estuarine flooding plains, fixed dunes/interdune and mobile dunes. These units represent the transition area between the continent and offshore region, beyond the territorial occupation of urban and industrial areas. The unit of Low Vulnerability corresponds to the planing surface that represents mostly the southern portion of the study area. The evolution analysis compared of the years 1989, 2000, and 2001, shows that this compartment remains quite stable, with only decurrent modifications due mobile dune migration and increases on agricultural, industrial and cities occupation.
On the results basis one can confirm that the applied methodology revealed efficiency on diverse multitemporal thematic maps generation (Soil, Geology, Geomorphology and Land Use for the years 1989, 2000, and 2001) by means of the multispectral images (Landsat 5-TM and Landsat 7-ETM+) colored composition and GIS integration. The multitemporal approach allowed the preparation of the Environmental Vulnerability Map. One emphasize the outcoming aspects:
The colored composite on RGB system RGB 7-5-3 and RGB 5-3-1 were of basic importance for limits definition between the landscape units useful for analysis and interpretation of land use changes during three distinct dates, following the changes occured due to human and/or natural action;
The RGB system colored composites of ratios RGB 7/3- 5/3-4/3, RGB 7/1-5/1-4/1 and RGB 7/4-5/3-4/2 mainly revealed efficiency for geomorphology units analysis and interpretation and for the comprehension of land use units changes comparing the coastal morphodynamic action with the main operating social-economic activities for the three distinct dates;
The Environmental Georeferencing Database and the GIS allowed the multitemporal analysis between three distinct dates based on comparative images integration for the years 1989, 2000, and 2001. These maps were integrated to the thematic maps (Soil, Geology, and Geomorphology) and allowed the preparation of the Environmental Vulnerability Map;
The comparative land use maps for the three dates presented the gradual replacement of the salt tanks by the shrimp farms. The construction and enlargement of the shrimp tanks toward the continent and nearby the cities and villas can provoke groundwater contamination and/or salinization;
beyond that, the ones found next or in direct contact with mangroves can cause heavy losses for the fauna and flora on this environment considered “the cradle of the sea life”;
CONCLUSIONS
·
·
·
· Soutoet al.
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Table 1.Environmental Vulnerability Indexes (levels High, Medium, and Low) for the geoenvironmental units described on estuarines regions of Rio Grande do Norte State, as defined by GEOPRO (2002) from specific data.
Plain
Fixed
Geoenvironment Unit Kind of Substratum Mobility Trafficlity Density of Biota
Indice of Environmental
Vunelability Tidal Plain Fine Sand, Silt, and
Clay
Low Very Low High Medium
Mangroves Fine Sand, Silt, and Clay
Low Very Low High Biodiversity High
of River Estuarine Flooding Fine and Medium Sand
High Low High Medium
Dunes/Interdune Medium and Coarse Sand
Medium Low Low Medium
Mobile Dunes/Interdune Fine and Medium Sand
High Low Low Medium
Planing Surface Medium and Coarse Sand
Medium High Low Low
Table 2.Information obtained from analysis and interpretation of orbital images, after a classification of the surface elements on the study area (SOUTO, 2002).
Combination Interpretation of Map R7/1-G5/1-B4/1 Land Use and Geology
R7/3-G5/3-B4/3 Geomorphology
R7/4-G5/3-B4/2 Geology, Geomorphology, and Land Use R7-G5-B3 Land Use (vegetation mangroves)
?
?
The geoenvironmental units definition have basis on the geologic-geomorphologic compartments; this in association to the land use comparative maps allowed to the characterization of the their relationship and the integration of geomorphologic evolution aspects with physical and biological elements;
The environmental vulnerability levels reflect the fragility conditions of the geologic-geomorphologic compartments to the land changes due to human activities and natural process imposed by the operating coastal dynamic events in the region;
These changes can cause many risks to the local population as also to the operating industries, based on predictable situations as oil spilling, groudwater contamination, infrastructures damage, among others. Therefore, the Environmental Vulnerability Map must be considered for the decisions making and planning of companies installations and population growth policies in the region.
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ACKNOWLEDGEMENTS
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The authors thank ANP (Agência Nacional do Petróleo) for the concession of master scholarship to the first author through the Human Resources Program (PRH-22); the Project PETRORISCO (FINEP / REDED 05 / CTPETRO / CNPq) for financial support; the Pos-graduation Program in Geodynamics and Geophysics and the Geology Department of Rio Grande do Norte University for availability of basic infrastructure necessary for accomplishment of this research.
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