The proliferation of slums in Brihanmumbai is the direct outcome of its teeming millions growing at a great pace. The initial `island' city, south of Mahim and Sion had engulfed Trombay and most of Salsette (the area north of Mahim-Sion and south of Vasai creek) through two expansions of municipal limits by 1960. Today, the urban sprawl of Brihanmumbai has already devoured the northern fringes of Salsette in Thane taluka. Repeated surges of the human tidal wave have flowed across Vasai and Thane creeks, and a Metropolitan region has emerged.

The population of Brihanmumbai today is estimated to be around 15 million. This numerical growth isessentially a post-Independence phenomenon, generated by in-migration from the districts of Maharashtra on one hand, and from neighbouring states on the other. Job opportunities in the expanding industries, financial institutions and administration have made the city attractive. The age and sex selective in-migration of the earlier days have transformed into family migrations over decades. Natural growth of the resident population is accounting for an increasing proportion.

Insularity and the north-south linear configuration have necessitated a northward urban sprawl of the city from the south end, first into northern sections and later into Salsette and Trombay. The northward growth is still continuing unabated along the traffic corridors and in recent years augmented by an eastward march across the Thane Creek. Mumbai today is more a conurbation than a sharply defined `million' city.

Parel was an outlying suburb of the British fort city in early nineteenth century. Then came the textile industry andParel became central Bombay, with new developments around Dadar. The third and fourth decades of this century saw the rise of Shivaji Park area, Matunga and Mahim as the outlying suburbs. Apart from Bandra and Kurla, Salsette and Trombay were then supply villages of perishables to the city.

Independence brought in its wake a vigour and dynamism with the city's newly added port functions. Industries, commerce and banking too were on a fast pace of growth. Large waves of immigration from far and wide was the concomitant result, worsened by inflows of refugee population. Refugee colonies were set up in Sion-Koliwada, Chembur and Bandra apart from the distant Ulhasnagar. Khar was planned as a `model' suburb, but ceased to be so, before long. By the sixties, the inner suburbs in southern Salsette and Chembur-Trombay had emerged. The seventies and eighties saw the assimilation of the `extended suburbs' beyond Vile-Parle and Ghatkopar.

The northern fringes of Salsette beyond the municipal limits have been suckedin in the suburbanisation process in the last decade. Conceived as a counter-magnet to Mumbai, Thane, Vashi, Belapur have emerged merely as extended suburbs.

In this process of suburbanisation, a spatial order of succession (step by step growth) is evident. The northward creep along the rail-cum-road corridors, crystallising into dormitories around the rail head is the first phase. The west side in each case is invariably developed first. The building of the Express Highways has brought a subsequent east side development. Built up areas extending outwards, away from the rail head is the next phase. Such extensions progressively spread over new reclamations on the creekside, and an upward creep on the hill slopes and levelled sites towards the central hill complex of Salsette. With the rail head as the focal point of commuter convergence, roads leading to the rail head have become shopping fronts. While the reclamation grounds house middle and upper class society, inevitably accompanied by hutments in theniches, the lower hill slopes of the central hill zone shelter innumerable shanties.

The dormitory character of early suburban development has undergone vast transformation following family in-migration. The cosmopolitan character of early Mumbai that was an urban mixture of groups of in-migrants living in closed communities has itself changed into a truly cosmopolitan character as the suburbs have matured into an urban amalgam of people of varied linguistic, religious, caste groups living together in harmony in open housing societies that are stratified more on economic grounds.

Today, less than a third of the population of Brihanmumbai lives in the `island' city. Nearly half lives beyond Vile Parle in the west and Old Kurla in the east. The centre of density of population has shifted from the island city well into suburban Salsette. With the `suburban' Mumbai growing faster than the island city, especially in its northern parts, the centre of density is bound to move further north in the immediatefuture.

The commuter traffic is no more one way into the Central Business District (CBD) in the south of the city in the mornings. Though it is still the main movement, movement in opposite direction is substantial and is gaining in strength, thanks to industrial jobs in the suburbs. East-west cross flows within the suburbs and beyond, into and out of Vashi and further outwards are also increasing. It is therefore not surprising that two-thirds of the BEST bus service is now focussed on the suburbs of Salsette, Trombay and beyond.Real estate is more active in the distant suburbs than in the city. Urban renewal is no more confined to the city. South Mumbai colleges and schools are concerned about falling numbers of students. Few of the residents of the suburbs today seek the markets and shopping arcades of South Mumbai or Dadar. The suburbs have become increasingly self-supporting, in terms of their needs of shopping, education and medical amenities and entertainment. Only civic amenities and infrastructurelag behind. The suburbs are no more suburbs. They have come of age, and have distinct identities as organs of the larger urban mosaic.

Where then are the present day and future suburbs of Mumbai? Perhaps Vasai to Virar on the Western railway, though a nightmare to planners as far as its water supply and drainage are concerned. Perhaps Airoli-Vashi-Konkan Bhavan-Kalamboli-Panvel, as more commuters to the city throng these areas. Perhaps even Mumbra-Taloja-Panvel as the Konkan railway picks up momentum.

(The author is the former HoD of geography, Mumbai University)