Environmental land use Change detection and assessment using with multi-temporal satellite imagery

Mohsen Ahadnejad
Zanjan University
E-mail: [email protected]

Introduction
Environmental protection is faced a critical problems due to several factors as the increasing population, demolishing natural resources, environmental pollution, land use planning as well as others. Presently unplanned changes of land use have become a major problem. Most land use changes occur without a clear and logical planning with any attention to their environmental impacts. Major Flooding, air pollution in large cities as well as deforestation, urban growth, soil erosion, desertification, are all consequences of a mismanaged planning without considering environmental impacts of development planes. Desertification is a common consequence of improper land use change.

Many authors have experienced employment of satellite imageries for land use mapping as well as change detection studies. Sunarar (1966) has compared the results of five different techniques of band combination, subtraction, band division, principal component analysis and classification in Ekitally, Turkey. This study revealed a better result in case of principal component analysis and comparison of the classification results. Gupta and Parakash (1998) used a combined method of color composite, band subtraction, band division and supervised classification to prepare a land use map for change detection studies in a coal-mining district in India. He concluded that the supervised classification gives a better result for detecting changes.

Lashkari (1377) has used probability index method and fuzzy to analyses multi-temporal TM imageries for land use changes detection mapping in city of Mashhad . Varasteh Moradi (1996) has employed Markoff Hierarchy to predict land use changes in Gillan Province.

At The present research supervised classification has been employed to study land use changes occurred in Maragheh region. Furthermore ecological models have also been used to analyze environmental impacts of land use changes in the area.

Study Area:
Study area is located between 37 14-37 30 north latitude and 45 59-46 16 east longitude. The area covers Bonab and Maragheh cities comprising the three topographic units of mountains, foothills and plain. The main reason to select this area is the considerable land use changes occurring in the area as urban development, rural development, Alavian Dam construction, and major changes in crop pattern in the area.

Methods of study:
Topographic maps of the area including 1:50000 and 1:250000 are digitized first. Then Landsat imageries of dates 1989 and 1998 are considered for digital image processing. The following flowchart shows the major steps of the study:

Fig 1: Flow chart showing the major steps of research
Geometric correction:
20 GCP were selected throughout the area using topographic maps. RMS is estimated around 0.87 pixel (25 square meter).

Classification:
Classification carried out using MLC method. First 741 (RGB) color composite is prepared. Then training area were collected based on 10 different land cover classes including water, wetland, salty land, sparse vegetation cover, moderate vegetation cover, residential, orchards including amygdales, apple trees and citrus, dry farming, outcrops and waste land, irrigated land. Editing is applied using aerial photos as well as maps. Overall accuracy is estimated around 97% (fig 2,3).

Fig 2: The classified image shows land use and land cover of the area in 1989
Fig 3: The classified image shows land use and land cover of the area in 1998.

Table 1: The results of analysis based on the comparison of image classification in 1989 and 1998

Qualitative evaluation of Land use and land cover changes with Environmental Impact Index:
Qualitative evaluation as well as the rate of land use -land cover changes carried out through the visual inspection of pollution rate caused by every land use. As an example in case of changes from agriculture land and orchards to construction and settlements we will have high rate of environmental Impact. The reason for using weighting method and also estimating pollution rate is the ease of process as well as obtaining a general classification of impact rate caused by different land use changes so it doesn’t necessarily shows the exact rate of pollutions caused by land use changes. Detailed studies are needed to obtain accurate figures. Table 2 represents the applied weights.
Table 2: weights assigned for every land use

 According to the obtained results the rate of impact due to land use changes are classified into 4 distinct classes as very high impact, high impact, medium impact, low impact.

The results of study also revealed that during the years of 1989-1998 the total area of about 879912 hectares caused environmental impact. Table 3 shows the results of changed area based on loss Index.
Table 3: changed area based on Environmental Impact Index

Considering the above table about 615.06 hectares of these changes were due to development of settlements as well as constructed lands over orchards, which occurred mostly on the urban fringe of Bonab and Maragheh towns and are of high impact. About 247.77 hectares of these changes mostly are related to changes due to construction and settlements build on agriculture land around Maragheh, which are recognized as an environmental impact. About 7033.77hectars of these changes, which are related to the natural resources and vegetation cover in the area are classified as moderate impact. Around 902.57 hectares of the land use changes in the area are classifies as low impact (low harm) that includes those changes due to extension and transgression of the eastern coast of Uromia lake. Fig 3 shows the final result after applying the environmental impact index in the study area.

Conclusion:
The results of study disclose two major distinct land use changes occurring in the area as followings:

1. those changes due to the extension of Uromia Lake, which develops wetlands and saline lands aroud the lake altering the vegetation, cover.
2. changes caused by development of industries, population growth, and construction of Alavian dam in northern part of Maragheh, and development of residential area. The results of research revealed that this type of changes have the most environmental impact in the area so that the continuation of such a trend may endanger the surrounding land as well as the orchards in the area. So it is recommended to protect this critical area.

Reference:

• Jensen J.R, “Introductory Digital Image processing”, (1986).
• F. Sunar,”An Analysis of changes in a Multi – data set; a ease study in the Ikitelli area Istanbul Turkey”, Int, J, Remote Sensing, (1998). Vol.19.
• A.Parakash and R.P Gupta,”Landuse mapping and change detection in a coal minnig area, a case study in the Jharia coalfield, India”, Int. J. Remote sensing (1998). Vol. 19.
• M.F.Makhdoum, “Fundamental of land use planning “, Tehran University 1994.