Remote sensing applied to slope stability in mountainous roads in Iran
The Alborz Mountain range separates the northern part of Iran
from the southern part. It also isolates a narrow coastal strip to
the south of the Caspian Sea from the Central Iran plateau.
Communication between the south and north until the 1950's was
via two roads and one rail link. In 1963 work was completed on a
major access road via the Haraz Valley (the most physically hostile
area in the region). From the begining the road was plagued by
accidents resulting from unstable slopes on either side of the valley.
Heavy casualties persuaded the government to undertake major
engineering works to eliminate ''black spots" and make the road safe.
However, despite substantial and prolonged expenditure the problems
were not solved and casualties increased steadily due to the increase
in traffic using the road.
Another road was built to bypass the Haraz road and opened to
traffic in 1983. But closure of the Haraz road was still impossible
because of the growth of settlements along the route and the need for
access to other installations such as the Lar Dam.
The aim of this research was to explore the possibility of
applying Landsat MSS imagery to locating black spots along the road
and the instability problems. Landsat data had not previously been
applied to highway engineering problems in the study area. Aerial
photographs are better in general than satellite images for detailed
mapping, but Landsat images are superior for reconnaissance and
adequate for mapping at the 1 :250,000 scale. The broad overview and
lack of distortion in the Landsat imagery make the images ideal for
The results of Landsat digital image analysis showed that certain
rock types and structural features can be delineated and mapped. The
most unstable areas comprising steep slopes, free of vegetation cover
can be identified using image processing techniques. Structural
lineaments revealed from the image analysis led to improved results
(delineation of unstable features). Damavand Quaternary volcanics
were found to be the dominant rock type along a 40 km stretch of the
road. These rock types are inherently unstable and partly responsible
for the difficulties along the road.
For more detailed geological and morphological interpretation a
sample of small subscenes was selected and analysed. A special
deve loped image analysis package was designed at Aston for use on a
non specialized computing system. using this package a new and unique
method for image classification was developed, allowing accurate
delineation of the critical features of the study area.