781
19°
73°W
lents in the
which appear
id the river.
5 DISCUSSION
The coastal scenery as depicted by ¿he sate
llite imagery is one of a highly indented
shoreline with creeks, promontories, cliffs,
bays and beaches. There are also extensive
marshy tracts; at a few places along the
coast, raised beaches occurring 3 m. above
the present sea-level and a band of littoral
concrete are observed at Versova and Madh
promontory respectively. The creeks keep to
NE-SW, north-south and NW-SE trends.
The raised beaches, the littoral concrete
and the marshes indicate a period of emer
gence of the Bombay region sometime in the
past. This might have occurred consequent
on the coastal faulting which is generally
believed to have taken place all along the
West Coast after the eruption of the Deccan
Volcanics; Radhakrishna (1957) has given a
Miocene age to this fault. The resultant
coastline must have been straight.
This faulting, which represents a failure
of the volcanics by rupture, has been prece
ded by plastic deformation of the volcanics
which is reflected in the monoclinal flex
ure described by Auden (1949) , the Panvel
flexure; this is an important lineament of
the Konkan region. Subramanyan (1981) has
shown on the basis of field evidence that
the Thane Creek has developed over the ten
sion fracture trending north-south that has
formed along the axis of this flexure at the
southern end. Concurrently, shear fractures
trending NE-SW and NW-SE appear to have
opened out in the volcanics in the Bombay
region. These shear fractures have control
led the courses of the creeks in the Bombay
island and the adjoining Nhava-Sheva-Uran
area in the east (Fig.2). In the latter area
the lineaments intersect mutually to form a
triple junction, cutting asunder the whole
region and initiating the process of marine
erosion.
A retrogradation cycle of marine processes
had set in subsequently and gradually conver
ted the initially straight coastline into a
highly irregular, indented shoreline of the
'ria* type. Many bays have already been for
med in the south - the compounded Back Bay
and the perfect Mahim Bay. Due to intense
urbanization in the Back Bay area, the ero
siona! processes have been interfered with
and they appear to have shifted their acti
vity to the north. The intense erosion that
is taking place south of Versova with a rhy
thmic regularity every year appears to be
partly due to this human interference. The
Madh promontory also appears to be refract
ing the waves on to this stretch of the coa
st which lies on the same latitude as the
former. Significantly, the localities to
the north and south of this stretch are free
from erosional damage. The growth of a spit
from the mouth of the Malad Creek in the
Versova area is interesting; for, it may be
able to prevent the severe erosion south of
Versova if it gains height when it will take
up the brunt of the wave attack, itself.
From this point of view as well as from the
point of view of the suitability of this
stretch for developing into an harbour, if
required later, this spit is being monitored
by Shetty and Subramanyan (1985).
It is to be expected that, due to the ope
ration of the retrogradation cycle, all the
bays and promontories will be eliminated and
that the coastline will restore its original
straight configuration in a few million
years.
6 CONCLUSION
Satellite remote sensing by itself has pro
vided significant data adequate to trace the
development and evolution of the Bombay
coast. Supplementary data from the maps and
field work have helped to complete the pic
ture.
REFERENCES
Auden,J.B. 1949. Dykes in western India.
Trans, nat. inst. sci. India. 3:123-157.
National Atlas Organization. 1964. India:
Physiographic regions, plate 41.
Radhakrishna,B.P. 1967. The Western Ghats
of the Indian peninsula. Proc. sem. geom.
stud. India, univ. Sagar. 4-14.
Shetti,Vi & Subramanyan,V. 1985. Spit simu
lation - an approach for Yersova, Bombay.
Sixth axm* ! meet. inst. Indian geogr. abs.
Subramanyan,V. 1981. Geomorphology of the
Deccan volcanic province. Mem. geol. soc.
India. 3:101-116.
