Journal of Coastal Research SI 39 1635 - 1637 ICS 2004 (Proceedings) Brazil ISSN 0749-0208

FRANÇA, F. A. N. de; AMARAL, R. F. do and PEREIRA, D. de A., 2006. Land use mapping and change detectionassessment in the eastern littoral zZone of Rio Grande do Norte State, Brazil, using GIS techniques. Journal ofCoastal Research, SI 39 (Proceendigs of the 8th International Coastal Symposium), 1635 - 1637. Itajaí, SC, Brazil,ISSN 0749-0208.

This work presents the survey and evaluation of changes on the coastal area of Rio Grande do Norte State,Northeastern Brazil, between the municipalities of Maxaranguape and Rio do Fogo, using Geographic InformationSystem techniques and remote sensor images from 1969 and 1999 (aerial photos and ETM/Landsat 7 image,respectively). The study area is limited by UTM bearings 230KmE and 254KmE and 9,416KmN and 9,387 KmN(UTM zone 25 South) - SAD69. The aerial photos were digitalized, resulting in images with approximately3m of spacial resolution. The aerial photos and ETM/Landsat 5 sensor images were registered using theETM/Landsant 7 sensor image and the ER Mapper 6.0 software.Afterwards, all the imagery was visually vectorizedusing ArcView GIS 3.2 software. The objects were identified by numbers in order to separate each diferent featureand help to calculate their areas and other attributes. The main features visually classified in the study area wereriver-beds, lagoons, dune bodies, fluvial plains, landuses and unclassified areas (i. e. areas located between dunesand fluvial plain). The most important changes found occurred in the cost line, due to erosional and depositionalprocesses; with the cover of the dunes, due to variation of vegetation or ocupation; populational growth of cities orvillages, that already ocuppies areas of erosional risk in few years. The studies allowed the determination of severalchanges that occurred in the study area during a 30 years period. The quantification of these changes was based on avectorial analysis.

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ADDITIONAL INDEX WORDS: Maxaranguape river, coastal erosion, coastal changes.

ABSTRACT

Land Use Mapping and Change Detection Assessment in the Eastern Littoral Zoneof Rio Grande do Norte State, Brazil, Using GIS Techniques

F.A. N. de França † R. F. doAmaral‡ and D. deA. Pereira;

INTRODUCTION

The study area is located between the municipalities ofMaxaranguape and Rio do Fogo, northeastern littoral zone ofRio Grande do Norte State, Brazil. It is limited by UTMbearings 230KmE and 251KmE and 9,416KmN and9,387KmN (UTM zone 25 South, SAD69) (Figure 1).

Trade winds from NW are the predominant winds and have

an average speed of 4,35 ms . These winds are responsible forthe rainy months and dune changes. There are two rivers in thestudy area: Punaú and Maxaranguape. Study area is dominatedby recent dune sediments and alluvium sediments that cover theCenozoic units (P , 1981)

Dune bodies can be covered or not by vegetation. There arealso several small lagoons with different forms. We can find twovillages in the study area: Pititinga and Maracajaú. Fishing,agriculture and turism are the most important economicactivities in this area. These characteristics give a high levelenvironment sensitivity to the area.

This work intends to survey and evaluate changes that occurin the study area during the study time (from 1969 to 1999),using GIS techniques, with a vectorial approach. Changes indune bodies, rivers, coastal line and vegetion were observed.

The imagery is composed by aerial photos from February 3 ,1969, with the approximate original scale of 1:70,000, andimages of the sensor ETM/Landsat 7, band 8, from November

19 , 1999. The ETM/Landsat 7 band 8 was choose because ithas the highest spatial resolution among all the bands of thissensor (15 m).

The aerial photos were digitalized in a table scanner with600dpi resolution, resulting in 3 m pixels images andmosaicked. In order to reduce errors due to deformation of the

periferic parts of each image, we used only the central part ofeach image. The images were cut in 20% along the same flightway and in 10% each side. With these procedures we used about50% of each whole image. The aerial photos were registeredindividually with ER Mapper 6.0 software (ERM, 2001) andbased on a previously georreferenced ETM/Landsat 7 image.The greatest RMS found was 5.93m (informed by the software).

The mosaic process with the aerial photos was carried out inorder to produce a image that represents the whole study area.We used the PanaVue Image Assembler 2.05 software to buildthe mosaic image. This mosaic image was registered, based onthe ETM/Landsat 7 image. The greatest RMS found this timewas 4.39m. After these procedures, we started the vectorizationof both aerial photo and ETM/Landsat 7 images using ArcView3.2 software (ESRI,1998).

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RATTES

METHODS

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†Departamento de Engenharia CivilUniversidade Federal do Rio Grandedo Norte, Natal,RN 59072-900, Brazilfagnerufrn@yahoo.com.br

‡ Departamento de GeologiaUniversidade Federal do Rio Grandedo Norte, Natal,RN 59000-000, Brazilric@ufrnet.br

Departamento de Engenharia Civil

Universidade Federal do Rio Grandedo Norte, Natal,RN 59000-000, Brazildiegoufrn@yahoo.com.br

Figure 1. Location of the study area, between the municipalitiesof Maxaranguape and Rio do Fogo, Rio Grande do Norte, Brazil.

Journal of Coastal Research Special Issue 39, 2006,

We selected areas that presented biggest changes in shape

and position 1999). Each identified feature

received a number in order to evaluate attributes like superficial

area projection in a plain. The accuracy of this method was

limited by spatial resolution of ETM/Landsat 7 image band 8

(15 m).

Changes in Punaú and Maxaranguape rivers, mainly in

Punaú River estuary (Figure 2) where occurred the formation of

two small lagoons (about 23,110m² and 3.672m²). It is possible

to notice the presence of human action because of the

retification of Punaú riverbed in some places.Natural vegetation areas were reduced to about 50% of the

amount in 1969 (259.37 Km² in 1969 to 138.56Km² in 1999).

Culture area was increased about 190% in this period (54.05

Km² in 1969 to 165.11 Km² in 1999) (Figure 3).Dune area without vegetation cover has reduced almost 45%

during the study period.Pititinga and Maracajaú have had a extraordinary growth.

The area of Maracajú increase about 920% and the Pititinga

area increase about 1,230% (Figure 4A).Erosional processes in Ponta do Coconho have provocated

coastal erosion about 100m during the study period (Figure 4B).

These processes can form a little sand bank near the coast in

Ponta do Coconho and in other southern areas. Pititinga may

suffer engineering problems in ten years if the erosional speed

continues as it is.

(MITCHELL,

RESULTS

Main Changes Found in the StudyArea

The main features classified visually in the study area were

rivers (Punaú and Maxaranguape), lagoons, dune bodies,

fluvial plains, villages (Pititinga and Maracajaú), cultures and

natural vegetation. Lagoons did not suffer great changes during

the study period. However, some features have presented

important changes (Table 1).

França .et al

Figure 3. Changes in vegetation cover. Natural vegetation areaswere reduced to about 50% and culture area has increased about190%.

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Table 1. Area of features that has presented the greatest changesduring the study period.

Plantation Area 54.04 157.94 + 192.26%

NaturalVegetation

259.37 138.56 - 52.42%

Pititinga Village 0.35 4.65 + 1,228.57%

Maracajaú Village 0.14 1.43 + 921.43%

Dune withoutvegetation

31.18 17.63 - 43.46%

Greatest Change

Features 1969 1999

Percentual

Change

Area (km )2

Figure 2. Changes in Punaú river. It is possible to notice the formation of two small lagoons close to the estuary.

Coastal Change Detection

CONCLUSIONS

This study allowed us to determine and evaluate some

changes in the study area. On one hand, some of these changes

were carried out by human beings action. On the other hand,

others were produced naturally.

This study found out that the risk of engineering problems in

Pititinga village is iminent due to erosional rate observed. The

erosional process next to Ponta do Coconho was about 100 m in

30 years. If the erosion process speed continues as it is, the

coastal line will reach Pititinga village in 10 years,

approximately.

Change in vegetation cover was intense. Culture areas have

increased almost three times, which represents human action.

The lost of vegetation areas happen due to increasement in

Pititinga and Maracajaú villages and culture areas.

Change in dunes without vegetation cover may be caused by

differences in the months the images were taken.

LITERATURE CITED

PRATES, M. GATTO, L. C. S., COSTA,

MITCHELL,

M. I. P. Geomorfologia.

In: PROJETO RADANBRASIL/ Ministério das Minas e

Energia. Folhas SB. 24/25 Jaguaribe/Natal. Rio de Janeiro,

1981. 301-348p. (Levantamento de Recursos Naturais).

ERM - Earth Resource Mapping LTD., 2001, Using ER

Mapper. 361p.

ESRI - Environment System Research Institute - INC, 1998,

ArcView Version 3.2 software handbooks.

A., 1999.

Redlands,

California: Environmental Systems Research Institute, Inc.,

188p.

The ESRI Guide to GIS Analysis, Volume

1: Geographic Patterns & Relationships.

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Figure 4. A) Growth of Pititinga village. B) Greatest coastalerosion in the study area.