Parviz Tarikhi, 1999

 

 

CHANGE DETECTION IN NORTH WESTERN IRAN

 

We live in an era that the problem of environmental protection is one of the major problems. The unprecedented rate of scientific and technological progress creates an intense human pressure upon natural systems. In such an era, almost all of the countries have been obliged to step for protecting their environment. Lake Orumiyeh National Park (LONP) is one of these protected sites.

LONP sited in Northwest of Iran is the greatest domestic lake of country with 130-km length and 40 km maximum width. While the lake's total area exceeds to 4636 sq. km, its average depth is 5 m. Being 1274 m over the free waters with the annual precipitation of 400-600 mm the lake's temperature varies from 17 to 36 (C) yearly.

High concentration of saline water makes the lake a favorable place for recreation since you can float over the water without sinking. Depending on the different places and seasons the degree of salinity in the lake varies but its average is 300 gr./lit. Consequently the water surface does not freeze in winters, and therefore is a favorite destination for migration of millions of migrant marine birds to the region from far lands.

The majority of the lake's water is supplied by the different rivers the most important of which lead to the lake in south. The Lake has a watershed area of 51300 sq. km covering part of the northern Azerbaijanian Mountains. There are 102 islands at the lake, the total area of which exceeds to 334.86 sq. km while only five islands have an area of 326.40 sq. km totally. Shahi, the greatest island at the lake -sometimes a peninsula due to water surfface downing- is the only habituated place at lake with the total area of 25.25 sq. km.

In spring and summer the lake becomes the greatest region for reproduction of some birds including flamingos. Their food is the shrimps of saline water. Ducks also recreate at the lake. In fall and winter the lake changes its appearance and quietness and stillness dominates.

LONP is not exclusively the habitat for birds. Wild mammals such as hamsters, rams, ewes and tigers live in some of the islands. Despite the water salinity of the lake its islands as well as most of its coastal zones is covered by the variety of plants such as pistachio, peanuts.

In 1967 the government declared one of the islands as the protected area. This followed by declaring the region as the protected national park in 1975. The aim for protecting the lake was to preserve existing ecosystem of the lake and supporting the divers species of wild life and preserving the natural picturesque values of the lake and its islands.

 

HIGHWAY CONSTRUCTION CAUSES ENVIRONMENTAL PROBLEM

After the establishment of I.R. Iran, the move towards attaining self-sufficiency as a strategy and for meeting integrated national demands caused the great attention to development and construction of routes during the first and second Five Year Economical and Cultural Development Plan (1989-1993 and 1994-1998 respectively). Therefore the establishment and increase of roads for goods transport and human travel became a focal point. Provincial and rural side roads can play a determining role due to their importance in linking various regions to the main roads and the share they have in the transportation network since the connection between the main roads is only possible through side roads in provinces. These roads are built according to the regional needs and upon the decisions of the provincial planning committees.

Construction of the provincial road linking Tabriz and Orumiyeh was begun in 1979. The road is of length 14 km with a 1.4 km cut in the middle that separates its 11-km western side from 3-km eastern side. The people in both sides of the lake use the road to exchange their agricultural and industrial products. In 1995 the authorities declared the project national. Beginning the construction of the road the environmental impacts in LONP have begun to appear. The impacts have had physical, chemical, biological as well as economical effects on the region.

 

RS/GIS SOLUTION

The specialists in the Iranian Remote Sensing Center (IRSC) with interesting outputs implemented a research project to study the environmental impacts in LONP. IRSC as the only governmental organisation responsible to co-ordinate and supervise all national remote sensing activities in country aims to utilise earth space data for research, earth resources and environmental monitoring.

The main input for the project was frequent satellite data of region available in IRSC. For implementing the project, firstly the existing data sources were examined. Then selecting the field study sites the fieldwork took place for detailed investigations. Later on satellite data and other imagery were processed and analyzed.

Satellite images combined with raster maps, digital elevation models and vector data can provide users and decision-makers with a real world context for fully understanding the state. While high resolution optical (HRO) data taken from Landsat-TM gives a spatial resolution of nearly 30 m and temporal resolution of about 16 days, SPOT data has the resolution of 20 m in spectral and 10 m in panchromatic mode with a 26-day temporal resolution. Due to availability of optical data including Landsat TM and SPOT Pan and spectral data in IRSC, these data were applied for investigation and combinations of satellite imagery were used. Moreover, environmental information was also applied.

The data received from satellite required both calibration and geometric rectification to be usable to the authorities and managers. Image processing and GIS techniques were implemented with outstanding results on the data. To manipulate the images they were opened within ER Mapper 6.0. The data were first analyzed and interpreted using ER Mapper to overlay, combine and query data from multiple sources.

We performed system and terrain corrections including de-striping, color balancing and mosaicing on our Landsat-TM and SPOT data collection. The coupling of ER Mapper data with AutoCAD and ArcInfo has synthesized all applicable information into a coherent system. Using ER Mapper we converted the vector files to AutoCAD successfully. ER Mapper is used to geo-reference and mosaic the imagery, and merged to form an image backdrop. Change detection comparing old maps and images with new images showed easily the place of new changes. It has simplified our data analysis process considerably causing increase of accuracy and improvement of decision-making results.

The imagery however, was given even greater value when combined with information from a GIS. We integrated GIS information from Autodesk World with our image backdrop from ER Mapper. The combination of data was simple since the ER Mapper technology is embedded inside Autodesk World.

Due to simplicity of visual interpretation we were able to query the database for more complex information. Image display and mosaic wizard enabled us to automatically display and mosaic new images. The image balance wizard also removed problems such as hot spots and visible edges in minutes. The available ER Mapper software allows saving to well known formats such as BMP, TIF and JEPG. In our project we saved our images in JEPG format.

Ortho-rectification enabled us to remove local distortions, which are inherent in earth space data. It placed the digital image in its true geographical position, suitable for inclusion as a separate data layer within the related GIS.

After processing saving the image in compressed format aided to data portability. The ER Mapper Compressed Wavelet (ECW) imagery format was created using the ER Mapper Compression Wizard. The compression combined with the ortho-photo, mosaic and color balance wizards provides a complete solution for processing and integration of imagery.

With the GIS plugins, we were no longer restricted by limited image handling capabilities. Using appropriate ER Mapper plugin we could directly read an ER Mapper image behind our GIS vector data. The images could then be used in the reports using the free ER Viewer or Power Point.

 

RESULTS

Image processing reduces the amount of processing time needed to combine data sets from different sources. Utilizing image processing and GIS save time, cost, and work.

As the information specialists, we provided decision-makers with relevant information to make informed decisions. For example one of the outputs of project was to establish a model to display the distribution pattern for sedimentation. The results show that the rate of sedimentation around the road has been change considerably during the years. Moreover, the results also show the effects of mismanagement for construction of the road. With the new satellite information we are able to provide corrected information about our environment.

New roads should avoid as much conflict as possible with existing protected areas such as LONP. This needs further studies and investigations using earth space and ground truth data.

The results of the project have been presented to some of the authorities and decision-makers. The signs for usefulness of the results can be seen applying them to reduce and mitigate the future impacts committing to proceed knowledgeably for protecting the LONP environment by improving our management methods as well as plans and programs for development.

 

 

Parviz Tarikhi is a researcher specialising in space science and technology in the Iranian Remote Sensing Center (IRSC). He can be reached at the address below:

IRSC, No. 22, 14^th Street

Saadat-Abad

Tehran 19979, Iran

E-mail: [email protected]

Fax: +98 21 206 4474

 

(Also thanks to Mr M. Jannati in IRSC for providing classified imagery.)

 

 

IMAGES

 

 

 

 

 

One of the picturesque calcareous islands in eastern part of the lake

 

 

 

 

 

 

 

Swimming in the clear and calm saline waters of the lake is a pleasant recreation.

 

 

 

These two satellite imageries taken by the Landsat TM sensor from the Lake Orumiyeh. The left image is taken on June 30, 1989 and the other on August 19, 1990. The difference in water level at different times can be distinguished easily.

 

 

 

Farmlands in Shahi Island

 

 

Big group of flamingos flying over the lake

 

 

 

 

Sh. Kalantari Highway in construction connecting Tabriz and Orumiyeh in east and west of the lake

 

 

 

 

 

 

 

 

 

 

 

The influence of road construction in the Lake Orumiyeh on the distribution of sedimentation. Top left image is a false color composite of bands 1, 2, 3 of SPOT-XS sensor acquired in 1986. The image's unsupervised classification is shown in bottom left. The top right image is also a false color composite of bands 2, 3, 4 of Landsat TM sensor acquired in 1991. The relevant unsupervised classification is shown in bottom right. The pattern of sedimentation has considerably changed from 1986 to 1991 and it is evident around the road that can be seen as a narrow line in the center of two images.