EVOLUTION OF MUMBAI-FROM ISLAND ENVIRONMENT TO URBAN ENVIRONMENT
Dr.V M Dehai Kulkarni,
Retd. Professor & Head of the Geology Dept.
K J Somaiya College of Science & Commerce,
Vidyavihar, Mumbai - 400 076.
Evolution of Mumbai during the last 300 years is an illustrative example as to how present day development: Economic, Social & Environmental have caused various problems for the inhabitants of Mumbai. Introduction: 1) Dr. Buist wrote in 1851 that Bombay Island for most part rose in to round or nearly flat topped hills varying in height from 100 to 1000 ft. At that time there existed a belt of Coconut trees adoring the Shores of Bombay having within it an infinite variety of Woodland, Mountain, Lake and River Scenery every where. According to him Bombay island scarcely surpassed in picturesqueness and beauty anywhere in the world. Within one hundred years there is a tremendous change in Bombay. Many of the hills like Mazagaon hill (150 ft.) Chinchpokli Hill (150 ft.). Matunga Hill, Tardeo Hill has vanished from Bombay's topography. Even the hills like Malbar Hill, Worli Hill do not look like hills now. Most of the hills in Greater Bombay have already been digested by our greed for more land and for housing industry & other activities.
Bacon has rightly pointed out 400 years ago that "Nature to be commanded must be obeyed"! Any interference with Natural process may have therefore unexpected effects elsewhere in course of time. In this context, it may be stated that a city can never be planned and designed in total disregard of its environment upon which it cannot be just imposed. The city must fit in at least with the topographic limitations of the chosen site. Consideration of the environment of the site is therefore one of the most vital parts in the complex process a part without which the planning-operations cannot proceed with any degree of certainity or true efficiency. Haphazard and local reclamation, distinction of hills, disturbing the earlier natural drainage of Mumbai Island, have affected Mumbai's environment.
Evolution of Mumbai during the last 300 years is an illustrative example as to how present day development: Economic, Social & Environmental have caused various problems for the inhabitants of Mumbai.
1) Dr. Buist wrote in 1851 that Bombay Island for most part rose in to round or nearly flat topped hills varying in height from 100 to 1000 ft. At that time there existed a belt of Coconut trees adoring the Shores of Bombay having within it an infinite variety of Woodland, Mountain, Lake and River Scenery every where. According to him Bombay island scarcely surpassed in picturesqueness and beauty anywhere in the world. Within one hundred years there is a tremendous change in Bombay. Many of the hills like Mazagaon hill (150 ft.) Chinchpokli Hill (150 ft.). Matunga Hill, Tardeo Hill has vanished from Bombay's topography. Even the hills like Malbar Hill, Worli Hill do not look like hills now. Most of the hills in Greater Bombay have already been digested by our greed for more land and for housing industry & other activities.
Gilbert Hill Andheri: - Nature's Geo-Architecture.
The fill has been excavated to procure construction material and also to provide space for housing colonies. After the Seminar on "Endangered Hills" in 1981 the author wrote to G.S.I, requesting to preserve this hill as "Geological Monument" now declared as "Heritage Monument" by the Govt. of India. It has become a centre of Geo-Scientific expedition for studying formation of "Columnar Basalt" by Geologists all over the world.
2) Man and Nature
Bacon has rightly pointed out 400 years ago that "Nature to be commanded must be obeyed." Nature has a remarkable way of balancing operations. Any interference with natural processes may have therefore unexpected effects elsewhere in course of time. In this context it may be stated that a city can never be planned and designed in total disregard of its environment upon which it can not be just imposed. The city must fit in at least with the topographic limitations of the chosen site. Consideration of the environment of the site is therefore one of the most vital parts of the complex processes, a part without which the planning operations can not proceed with any degree of certainty or true efficiency.
Geologically the city of Bombay is an unusually interesting area for an urban planner. Three hundred years ago Bombay consisted of seven islands. At the time it was the sea which had claimed the land. Nature had designed its own plan for Bombay. One of the important environmental conditions of Nature was that the Arabian Sea water to circulate freely around the seven islands. With the gradual increase in population of Bombay, the need for more space was felt. Man began to reclaim land from the sea and thus process of joining the seven islands of Bombay began. Since then, water is constantly being kept in check by putting bunds on the western shore. Hornby Vellard - a big wall to hold back the sea water was built in 1720 between Worli and Mahalakshmi. This shows that the struggle against water and the process of reclamation has been going on for centuries in Bombay. The Backbay reclamation is the culmination of this process. How for man will be able to disturb nature's plan and to what extent Nature responds to man's interference in her plan is the crux of the problem facing the urban planner.
3) Geological Setting of Bombay
The principal rocks in Bombay are volcanic. A variety of trap rocks are found here. The traps are interstratified with Sedimentary rocks of fresh water origin. At few places the traps rocks of fresh water origin. At few places the traps rocks are also covered over by marine alluvium of three or four different ages. From these facts and observations it is that there have been four distinct periods in the formation of the islands of Bombay. 1st is that of primary volcanic effusion, 2nd that of the deposit of fresh water strata, 3rd that of the Secondary volcanic effusion and 4th the deposit of marine strata.
4) Secular upheaval and Subsidence in Bombay
From the diversity of levels at which the various beds in Bombay are found and their dip indicates that there have been movements of the land. The submerged forests and the raised beaches in Bombay confirm such up and down movements of the land. Geological reports by H.J. Carter, Dr. G. Buist and Dr, Frayor indicate that Bombay area was subjected to succession of upheavals and depressions during the human period. At the present the depressing process seem to be still in progress. According to Belussov, corresponding member of the U.S.S.R. Academy of Sciences, Bombay coast is sinking at the rate of 0.02 mm per year. Thus, Bombay has a coast of Submergence. It has bays, estuaries and off lying islands. The North Kokan and South Kokan Coasts are coasts of emergence.
5) Drainage pattern around Bombay
The major three rivers which from a drainage pattern around Bombay are the Vaitarna, the Ulhas and the Amba. The Centripetal drainage pattern around Bombay is significant and supports the theory of overall depressing movement in Bombay with respect to the highlands around. The presence of fresh water intertrappeans (Sedimentary rocks) in Bombay further indicates that the earlier drainage around Bombay had a centripetal pattern and that the drainage focus for those rivers was also Bombay.
6) Reclaimation in Bombay
The wresting of land from the water is nothing new to man. There are to be found examples of land reclamation in almost every developed country. The Netherlands provides the most famous of all of "Winning land from Sea." When reclamation work in progress at present in the Netherlands is completed, seven percent of the total land will have been created by reclamation. This epic feat of engineering is an example of what can be done by a relatively small country, working against great difficulties but always on the basis of most complete preliminary geological information possible about all the areas to be gained from the sea. It was the worst flood disaster of February 1953 which forced the Netherlands Government to set up a commission to investigate with regard to control measures to be taken to prevent recurrence of flooding. The "Delta Project" is the fruit of the studies of the Delta Commission. It should be pointed out here that it is the Delta Project which has made the land of Holland a habitable place.
In Honkong a major runway for its important international airport was built on land reclaimed from the sea. Similarly the main runway for the airport serving Gibralter was reclaimed from the sea. In Japan great progress has made in reclaiming much needed land from the sea by the controlled deposition of Industrial waste. Bombay Back Bay reclamation Scheme is an outstanding example. The great demand for land in coastal urban areas is one of the important factors for using marginal lands for reclamation and development. In the modem world reclamation of the land from the sea is not an unusual feature and in Bombay reclamation process is intimately connected with its growth from the 17th Century. The author wants to emphasis here that consideration of the Geology of the area can add to sound planning and success of the reclamation project.
7) Geological hazards in Bombay due to reclamation
Planning in Bombay for urban development has to take into account not only local geology but also the relation of local landforms to the possibility of inundation by the sea under extreme Combinations of high spring tides and violent winds. Even through they are rare, they cannot be ruled out entirely. In Bombay, the sea water penetrates inland through the estuaries and creeks and seeps into the subsoil. The water also comes down the three rivers and their tributaries. During Monsoon, the rain water is added. All this water has to be kept under control if the land in Bombay is to remain habitable. The Versova beach erosion, the recurrence of floods in the Ulhas and Vaitarna rivers and the flooding of the low lying areas in Bombay are symptoms of the geological hazards due to reclamation in Bombay. These geological hazards may assume alarming proportions if not checked in time by proper planning.
8) Coastal problem in Bombay
The ceaseless movement of the Arabian Sea Water, the process of erosion and deposition, the wildness of storms and the cyclical effects of tides are all reminders of the dynamic forces of nature that are trying to change the face of the coast near Bombay. Building of bunds or a sea wall on the Western shores of Bombay may not be a safely measure against the might Arabian Sea. The mean wind spread during the Monsoon is 17 Kms. Per hr. mainly from west and South - West. During Monsoon, Gales abnormal high wind velocities reach 100 kms per hr. or more have been recorded. These winds generate violent waves in the Arabian Sea which will attack the Bombay coast also.
9) Hydraulic action of Waves
When waves break against rocky shore, the water exerts great force. On the west coast of Scotland pressure measured by dynamometers averaged as much as 1 ton per sq. foot. During a great storm at wick on Northern Scotland, a solid mass od stone, iron and concrete weighting 1350 tons was ripped from the end of a breakwater and moved inshore. The damage was repaired with a block weighing 2600 tons but 5 years later storm waves ripped it loose and swept it away. This example shows the potential of the force that the sea displays sometimes.
10) Storms and Floods
The February, 1953 flood disaster in the Netherlands and the November, 1970 flood in Bangladesh are reminders to Bombay-men. During February, 1953 flood disaster, dikes in Netherlands were breached and sea walls on the coasts of England were badly damaged. There was extensive damage to human life and property. Cyclones also originate in the Arabian Sea. Even though Arabian Sea storms are not of much consequence to the Indian weather, the storms may occasionally recurve and hit the west coast of India like the 1952 November cyclone that hit Bombay Coast. Have we taken any precaution and safety measures against such probable flood disaster in Bombay? Can Hornby Villared or other similar bunds withstand the future onslaught of the sea on the Western Coast? No doubt, the reclamation process at various places in Bombay raises the level of the land but one should not forget that the slow depressing movement in Bombay at the rate of 0.02 mm per year.
11) The problem of Versova beach erosion and flooding of law lying areas in Bombay during Monsoon.
Versova beach erosion may be cited as an example of the effect due to interference with natural process in Bombay. The incoming waves towards Bombay advance more rapidly through a deeper water opposite a bay or creek than through a shallow water opposite a headland. Thus, the waves assume the shape of a coastline they approach. The line of front of wave is modified during its inshore journey. The shallow waters of headlines like Kolaba point, Malbar point, Bandra Point and Madh Point arrest the forward progress of the waves sweep into the bays and creeks before being checked. Now, the Backbay and the Mahim bay are being reclaimed. This process of reclamation is holding back the waters of the sea at these two points. Thus, the waves can only enter Malad creek in the North. The floor of the Malad Creek shallows rapidly and because the western face of Bombay is more prone to the fury of the direct action of the Monsoon waves, plunging breakers thrust their waters with great violence on Versova beach. Geologically the Versova beach consists of mud flats which get eroded easily. It is obvious that reclamation of the bays and creeks in South Bombay and the soft nature of the mud flats of Versova beach are responsible for the Versova beach erosion.
Similarly flooding of the lowlying areas is due to the haphazard and localized reclamation in Bombay without taking into consideration the relation of local landforms to the possibility of floods by rain water. The reclamation process has made Bombay - man to fight the sea water, the river water and the rain water, the fight may be a long-drawn affair and a relentless too.
Sometimes one wonders had the Arabian Sea put a signboard saying "Trespassers will be prosecuted" then man would not have ventured to reclaim land from the sea. But what guarantee is there that the mighty Arabian sea will not prosecute the Bombay-man by creating violent storms and disastrous floods in future? Of late, there has been a debate as to the ownership of the offshore reclaimed areas between the state and the Centre? But everyone has forgotten that there is a third party to this dispute and that is the silent but mighty Arabian Sea - rightful owner.
12) The following steps are recommended for future urban planning in Bombay.
- The plan must take into account the geological and foundation conditions in various parts of Bombay.
- The plan must be reconciled with the main environmental features of Bombay.
- Drainage of the Site (Bombay) will have to be studied in detail. Since man has to fight and remove access water from the habitable area.
- A small scale hydraulic model in which the action of moving water on a scale model of the site may be prepared for study.
- "Prevention is better than cure." So proper, systematic town planning is a better solution to disaster management.