CHAPTER 4: FACTORS INFLUENCING MUMBAI FLOODS

About 100 years ago, if Mumbai city were to receive a rainfall, as heavy as the one witnessed in the monsoon of 2005, its outcome would not have been as catastrophic. This is because the population of the city has grown to ten times of what it was a century ago. To accommodate this population, the city has risen vertically, open spaces have shrunken, the arterial roads cannot be widened any further and the drainage systems fail to keep pace with the ever-increasing requirements of the metropolis. Thus, this natural catastrophe that shook the Mumbai region in 2005 can be ascribed to three main factors as stated by Dr. Kelkar: (1) Unusually heavy rains and rise in sea-levels, (2) Antiquated building regulations and (3) The inefficiency of the existing drainage system, necessarily in that order. These causes are discussed in detail in the following section. What added to this disaster was the lack of a precise preliminary warning from the weather department. Moreover, the absence of post-disaster management plans on the part of the city’s governing authorities further compounded the situation.

Since the discharge of all the storm water and treated sewage is released into the Arabian Sea, tidal variation also constitutes a major component in the system of the storm water drainage (SWD). It results in excessive flooding and water retention in the event of heavy rains and the water recedes only during the low tide. This phenomenon was largely observed during the floods of 26th July 2005, when high tide forced all the drained storm water from the Arabian Sea back into the city.

1. Unusually Heavy Rains and Rising Sea-levels:
1.1. Climate Change and Heavy Rains

Heavy rains to a magnitude of more than 240mm are almost of a regular occurrence in Mumbai at the onset of the monsoons.

However, after the monsoon sets in and moves into its active phase, the situation is conducive to the occurrence of very heavy rains over Mumbai, when they are collectively a result of the following factors: “(1) Development of a low pressure belt over the sea, (2) Intensification of the monsoon trough and the development of embedded convective vortices over central India, (3) Amplification of the Arabian Sea current of the monsoon and (4) Super-positioning of a meso-scale ‘Off-shore Vortex’ over the northeast of Arabian Sea and its northward movement. All these conditions build up a synoptic situation that is conducive to the occurrence of a heavy rainfall in the area.” This phenomenon was largely observed in 2005.

Offshore Vortex: It is a rare meteorological phenomenon, characterized by a heavy but extremely localized rainfall that spreads over an area of, as little as, 30 square kilometers. Scientists and experts claim that in the case of the Mumbai floods, the phenomenon started with high velocity air currents in the Arabian Sea, which turned at 360 degrees, giving rise to a trough. The turn gave rise to a vortex, which resulted in a low pressure. In the meanwhile, powerful winds rose up in the atmosphere, leading to a heavy downpour.

However, there is a scientific explanation for the occurrence of this rare phenomenon. The reason, as Dr. R. K. Pachauri explains, is global climate change, in addition to the city’s geographic proximity to the Sahyadri Hills, that has played a significant role in the intensity of the downpour of July, 2005. Even as this research is in progress, current climatic changes worldwide have been exhibiting unexpected behavior and have been a constant cause of concern for all.

All scientific studies confirm that this “climate change is significantly anthropogenic (i.e. human induced).” One of the most predicted effects of the global climate change is extreme variations in tropical climates, including irregular rainfall patterns. An example of this phenomenon was witnessed in the form of heavy rains in Mumbai on 26th July 2005. The immense loss of life and property caused by this event are testimony to the fact that the impacts of climate change can add significantly to the vulnerability of the locations and communities that face the danger of natural disasters anyway. The human influence on climate change is caused by a rise in the concentration of the so-called greenhouse gases (GHGs) in the earth’s atmosphere. The most prominent among these is carbon-dioxide, which has been emitted, in increasing quantities, from the burning of fossil fuels, since the beginning of industrialization, in the mid-19th century. As a result, by the end of this century, temperatures would go up by anywhere between 1.4 and 5.8 degrees Celsius. This increase would have impacts in the form of erosion of the coastal areas, threats to the existing ecosystems and biodiversity and problems with the supply of water. Sea levels would rise and create further risks from storm surges for populations that inhabit small island states, low-lying coastal areas and floodplains. On the whole, the changing climate would unevenly impact the developing nations and the impoverished within all the countries with a similar geographical background as that of Mumbai. Floods are also likely to get more frequent and severe in the rest of India. All of this means that we would have to create mechanisms and infrastructure by which we would have early warning about the impeding changes in the climate. For this purpose, a modern and responsive meteorological system should be set up in the most vulnerable areas. The cost to be incurred in establishing such facilities would be “justified by the substantial reduction in the damage to property and the threat to human life.”

However, as mentioned earlier, the adverse consequences of the inundation of Mumbai were further aggravated when the rains were followed by floods. These floods were mainly a result of a rise in the sea level and an inefficient drainage system.

1.2. Rising Sea-level

A gradual rise in the city’s sea-level and a high tide were highly instrumental in the intensity of the Mumbai floods. Floods in the coastal regions usually occur when there is a rise in the water levels, as a result of heavy storms. When storm tides exhibit a continuous increase over the normal high tide, it is termed as a storm surge. “The maximum intensity of a storm surge is accompanied by a high tide; therefore, storms that persist through several high tides are most severe and these lead to severe flooding.” Mumbai, being a coastal area also experienced a similar storm surge. As Dr. Kelkar puts it, in the case of Mumbai’s inundation, “the term flooding is a misnomer to a certain extent, as it is not a result of the water spilling over from a flooded river. It was an inundation caused by the accumulation of heavy local rainfall and the inability of the drainage process to match the rainfall rate.” Additionally, as stated by Dr. R. K. Pachauri, a rise in the sea-level, which forced the storm water back onto the land, was also equally responsible in bringing about this event.

This rise in the sea level is primarily a result of the global climate change that “is unequivocal. This fact is now evident from an observed increase in the global average air and ocean temperatures and the resulting widespread melting of snow and ice” at the polar caps. In addition to the global climate change, the extensive reclamation of land from the sea has also been a cause of the rise in sea-levels. event of a heavy downpour and a high tide, residential, port facilities and various business generating sectors, located in the city would face immense flooding. Tourism would also be adversely affected, if the beaches and “tourist infrastructure like hotels and lodges” were to suffer flooding. Mumbai has a large population of fisher-folk living along the coast. Therefore, shoreline fishing would also be affected if “fish habitats in the reefs and estuaries were to be disturbed due to a rise” in the sea-level.

But again, there is another significant cause to such an alarming rise in the sea levels and this cause is primarily man-made. The explanation for this phenomenon could be traced in the rampant reclamation (Adjoining picture) that has been carried out along the coast of Mumbai as well as along the banks of the city’s natural drains. A detailed description of this development and its consequences are discussed in the following section.

1.3. Extensive Reclamation and Faulty Zoning Regulations

It is evident from the city’s planning history, discussed in Chapter 2, that in the process of housing construction and setting up industries, the waterways that allowed the accumulated rain water to drain out, have been drastically reduced. The reclamation that was carried out originally only to link the seven islands of Mumbai was eventually performed to a greater extent to accommodate the ever burgeoning population of the city Large slum colonies as well as planned constructions are being developed on the land reclaimed from the sea. However, some of this development has extended further to encroach upon the city’s existing storm water drains, in order to meet the housing demand of the city’s growing population.

According to certain officials from the city’s municipal corporation, the government has justified the rampant reclamation in the city by citing a “faulty’’ report prepared of Trivandrum-based Centre of Earth Sciences (CES). The CES in its report has obliterated many areas that were earlier in the jurisdiction of the Coastal Regulation Zone (CRZ) and shown them outside the prohibitory area. Even the big patches of mangroves in this zone have gradually disappeared as a result of this plot. The report thereby made way for the rash developments, which were otherwise not permissible.

“Mangroves are known to be a vital link in the ecological chain, serving as a buffer between the land and ocean. Thus, their destruction disturbs the ecological balance.” However, developers pay little heed to this fact and ignore the coastal zone regulations to continue with their reclamation. As explained earlier in the city’s planning history in Chapter 2, these developers lobby with the local authorities to reclaim and concretize the city’s coastal areas. They end up destroying the mangroves in the process, to make way for further development. The rapid and extensive concretization of these patches of land has now led to the reduction of: (1) Infiltration rate of rainwater and (2) Availability of depression storage on the earth’s natural surface. This breach of trust with the nature has eventually led to the nature paying back in the form of disastrous floods.

However, it is the city’s inefficient drainage system that claims a lion’s share in contributing to the magnitude of the Mumbai floods. Similarly, the outdated building regulations, that have been applied to develop the city, have also been instrumental in a substantial loss of human lives and property.

2. Outdated building Regulations

Although Global climate change has been observed almost since the 1970’s, their unpleasant effects were not alarming enough for the governments and planning authorities of cities around the world, to sit and take notice of. Thus, Mumbai’s authorities were never prompted to draft new planning policies, considering the new climatic pattern. This has also been true in the case of the city authorities of Mumbai. Prior to 26th July 2005, the city’s existing zoning and building regulations, that were drafted almost three decades ago, were used to scrutinize and regulate the new developments. They regulations failed to consider the factor of the rapidly changing local climate. Mumbai, which is known to receive an annual rainfall of around 240mm, restricted only to the months of June-September, now bears a downpour of almost eight times the average expected rainfall, in addition to the untimely winter showers. However, none of these have been considered to draft new planning policies for the city that can prevent the inundation caused by these rains and the rising sea levels. Most of the new developments permit the construction of basements, underground pedestrian bypasses and habitable space at ground level. Also, numerous old and abandoned buildings are being revitalized and remodeled to be used for a different purpose. However, the change of use of buildings from “ordinary to critical functions is carried out without strengthening the building" and without considering the climatic changes in the region. In the event of the floods, these areas get water-logged, causing destruction of life and property at large. These woes are added to by an antiquated drainage system that has been serving the city since the past century. Moreover, there has also been a blatant ignorance on the government’s and planning authority’s part to promote sustainable building construction.

3. Faltering Drainage Systems:
3.1. Mumbai’s planned Storm Water Drainage (SWD) System

Mumbai’s existing storm water drainage system has largely contributed in the inundation of the city. The city’s storm water drainage system is basically a complicated system of simple drains and rivers, creeks, drains and ponds. “The network comprises of a hierarchical system of roadside surface drains (about 2,000 km mainly in the suburbs), underground drains and laterals (about 440 km in the island city area), major and minor canals (200 km and 87 km respectively) and over 180 outfalls, which discharge all the surface runoff into the rivers and the Arabian Sea (Adjoining figure).”Of these outfalls, some drain directly into the Arabian Sea, while others empty into the Mahim creek, Mahul creek or the Thane Creek. Additionally, some out-falls that drain out storm water from the western suburbs empty directly into sea while the water from the remaining ones is discharged into the Mithi River which ultimately joins the Mahim creek.

3.2. Mumbai’s Natural Drain: Mithi River

The Mithi River (Adjoining figures) constitutes a major component of the city’s SWD system. The location of the river is important from the point of view of the city as it serves as a dividing line between the city and its suburbs. Thus, its flooding has direct or indirect repercussions on the disruption of the traffic on the five transport corridors viz. Central Railways, Western Railways, Western Express Highway, Eastern Express Highway & the Harbor Railway Line. The storm water drainage of the river is encroached upon by a large number of hutments, storages, processing industries, workshops and scrap yards situated along its banks. These settlements make it difficult even to define the path of the river. Direct discharges of the untreated sewage, wastewater, trash from the unauthorized settlements and industrial effluents flow into the river’s course and choke it up, thus raising the level of water during heavy rains. Similarly, most of the other storm water drains carry sewage and dry garbage in summers which clog them and disrupt the natural flow of rain water. Moreover, illegal settlements and reclamation for future development further reduce the existing width of the river they are built on. These result in the “reduction of the river’s natural storage and aquifer recharge.”

3.3 Major Drawbacks in the Existing Drainage network

The storm water drainage system of Mumbai was built largely in the days of the British Rule in 1860, when the population of Mumbai was merely one-tenth of what it is at present. After the initial development, improving the drainage has never been a priority for the government. The system comprises of about 400 km of underground drains and laterals, built on the basis of the population and weather conditions of the times it was constructed in. This antiquated storm water drainage system is capable of handling rain intensity of 25 mm per hour at low tide. If the rain intensity exceeds 25 mm per hour and a high tide occurs, there is always a possibility of inundation. The city’s existing drainage system is designed to tackle a rainfall of normal intensity, with the assumption that there are no significant solids deposits in the drains. This is because the slope of the drains is supposedly designed to generate a self-cleaning velocity in the flow and is thus built to keep flooding relatively rare. But the fact is other wise. Most of the drains throughout the city have been found to be occupied by a substantial amount of garbage and other solid deposits.

The resulting decrease in the capacity of the city’s storm water drainage system has been proved by the disastrous effects of the inundation that hit the city of Mumbai on 26th July 2005. The city was caught unawares and un-prepared to deal with the crisis that followed the floods. It was not in the capacity of the city’s drains to let out the excess water.

3.4. Current Efforts in Maintaining the Drainage System

At present, the city authorities of Mumbai are working towards maintaining the existing drainage network with the help of certain mechanical equipment. The municipal corporation of Mumbai has a total of 63 such devices (Adjoining figure). These include amphibious dredgers, jetting and suction machines and other customized vehicle mounted equipment, among others for the de-silting and de-choking of drains. However, of the 63 devices, about 24 are over 8 years old and are rendered non-usable as per the ruling of Honorable Supreme Court/Regional Transport Office Norms. Moreover, poor workmanship and un-trained labor also result in a non-satisfactory job of cleaning the drains. In addition, there are several stretches along these drains that are lined and encroached by slums that restrict the use of such equipment. Also, the width of numerous drains is poached upon to accommodate other utilities. This further reduces the capacity of the drains to carry the storm water and the approachability for the drainage maintenance equipment.

Since the discharge of all the storm water and treated sewage is released into the Arabian Sea, tidal variation also constitutes a major component in the system of the storm water drainage (SWD). It results in excessive flooding and water retention in the event of heavy rains and the water recedes only during the low tide. This phenomenon was largely observed during the floods of 26th July 2005, when high tide forced all the drained storm water from the Arabian Sea back into the city.

In addition to the above-mentioned causes, the blame for the immense losses caused by the floods in Mumbai can be credited to the lack of proper equipment in the city’s weather bureau. The absence of modern technical tools prevented the city’s weather department from imparting precise warnings about the impending heavy rains to the citizens. Moreover, the lack of proper co-ordination amongst the various disaster management authorities in the city also delayed the relief operations, causing further damage.

Thus, a study of the most probable causes for the inundation of Mumbai city and its aftermath provides assistance to formulate the prefect strategies to mitigate each of the micro-issues originating from these causes.

However, the next chapter first scrutinizes the flood-management strategies currently adopted by Mumbai. A review of these strategies helps comprehend their drawbacks that prevented them from controlling the floods in the city.

CHAPTER 3: THE MUMBAI DELUGE

Every year, numerous cities from around the world endure injuries, property damages and other significant economic losses, as a result of natural disasters including earthquakes, floods and heavy rains. The losses resulting from these disasters cannot be solely attributed to their repeated occurrence. Alternatively, they can be credited to numerous other factors. Large metropolitan cities throughout the world attract millions of people who are on a look out for better job opportunities and a better life-style. These cities are hubs of various revenue generating sectors such as commerce, government, communication and transport and require the support of a complex network of infrastructure, including power supply, telecommunications, roadways, railways, airways and civic amenities such as water supply and drainage systems. Often, this infrastructure ages beyond the point of reliability, is left unattended and is therefore, incapable of catering to the ever-increasing needs of the city’s growing population. This infrastructure is thereby, highly vulnerable to major breakdowns resulting from natural disasters like floods and its breakdown translates into a massive blow to the functioning of all its revenue generating sectors. Mumbai is one such city, which largely depends on its infrastructure for its normal functioning.

As the country’s economic core, Mumbai has been witnessing a constant rise in its population, resulting in a brisk and haphazard development of the city. The “physical infrastructure to support the city’s economy exists, but it has been designed for few and is used by many; it is usually stressed. Moreover, the dense and sometimes, organic patterns of the city’s development are incapable of accommodating the extensions in the infrastructure. Intensive mixed land use is a characteristic of the city of Mumbai.” Furthermore, the government’s drive to accommodate the growth of the city overrides issues, such as improving the infrastructure and formulating natural disaster management plans, to deal with the city’s current climatic scenario and rapid development.

This negligence on the government’s part has reflected on the city in the form of the massive destruction caused by the inundation in 2005 and 2006. The city has witnessed numerous floods in the past. Until a few years back, the citizens associated these floods with a severe disruption and suspension of the city’s train services (Adjoining figure) on an average of twice a year, during the monsoon. The event would lead to a shutdown of the offices, businesses and educational institutions throughout the city. However, the effects of these floods have never been alarming and devastating enough for the city authorities to plan preventive and relief measures.

But, the heavy rainfall of 26th July 2005 and the inundation that occurred in 2005 and 2006 was something that the city had least expected. The weather observatory at Santa Cruz in North Mumbai recorded a rainfall of 944 mm. in a brief time span of 24 hours. However, the Colaba observatory, at Mumbai's southern tip, recorded barely 73 mm of rainfall in the same period. Figure 14 shows the flood prone areas of Mumbai. However, the rainfall over Vihar Lake was 1050 mm, which was even higher than in Santa Cruz. About five years ago, in July 2000, Mumbai had recorded exceptionally heavy rains with Thane recording 45mm, Santa Cruz 37mm and Colaba 250 mm of downpour. But the consequences were not as disastrous as the ones that followed the floods of 2005 and 2006. This goes to show that it was not so much of the rainfall, but the inundation, that was unprecedented. Never before had the metropolis experienced anything like this.

The floods and the Offshore Vortex (an unusual meteorological phenomenon) resulted in about 1000 deaths and misplaced about 100 people. It forced more than 52000 people to evacuate their dwellings and caused the city a financial loss of nearly US $1Billion. Reports, quoting the government officials, stated that these “floods were the worst to hit the city in the past 100 years.” Moreover, the high tides that coupled with the torrential rainfall at its highest intensity, in this sea-facing city, further compounded this disaster.

The deluge came unannounced. Despite moderate warnings from the weather bureau, the rain wreaked havoc. This is because the government and the citizens failed to gauge the gravity of the warnings announcing the impending heavy rains and high tide. They mistook it to be one of the seasonal notices given out by the meteorological department. But in reality, the rains of 2005 brought in the devastating floods that will continue to haunt the people of Mumbai for the rest of their lives. All of the city’s means of communications such as the phone lines and power supply collapsed, thus cutting off the city from the rest of the world. The city’s public transport came to a grinding halt, within hours of the city’s flooding; the airports flooded, resulting in the cancellation or delay of flights. Also, most of the city’s arterial roads such as the LBS road (Adjoing figure), the S.V. Road and major highways, such as the Western Express Highway and the Eastern Express highway in the suburbs were severely affected due to water logging and traffic jams, caused by a mass vehicle breakdown in the floods. The event left thousands of people stranded in the buses, trains and cars. A lot of deaths occurred when people, hoping for the floods to recede, stayed put in their cars and were choked up when their vehicles submerged in the steadily rising levels of the floods. The death toll also rose when those marooned in their work places, made way for their homes and were carried away by the high currents of the floods. Moreover, the termination of the city’s main power supply rendered the sewage pumps in the city dysfunctional. The city’s municipal authorities were thus compelled to open out its storm water drains to let out the storm water. However, this adversely resulted in the drowning of a number of people into those drains. The city’s main storm water drain, Mithi River overflowed and spilled out the sewage it is dumped with and this gave rise to a host of epidemics in the following days. To add to this plight, the heavy rains caused landslides in the hilly areas in the north-west part of the city that had been quarried to accommodate future developments. It claimed the lives of almost 65 people and left more than a hundred, homeless. The floods damaged nearly 50,000 residential structures and close to 40,000 commercial establishments. It is a loss that the city would probably never be able to recover from.

And the bad news is that, this is not just a unique event that the city can conveniently forget about. “According to all the responsible predictions, flooding will get worse than before in the coming future.” This means that Mumbai can expect to have similar or even worse flooding in the coming years. This fact holds true for every country and city in the world that bears geographical resemblance to Mumbai. Inevitably, more and more existing settlements in the flood plains will be frequently inundated. This would cause more disturbances in the city’s functioning and a loss of property and life. Thus, it is extremely critical for flood prone areas to come up with a fool proof plan to deal with this wicked disaster. The plan should essentially include pre-flood prevention strategies as well as post-flood mitigation strategies, some of which haven’t been executed in such cases in the past.

However, to come up with almost perfect strategies, it is extremely essential to examine the most probable factors that led to this catastrophe, which is what this study aims to achieve in the next chapter. A review of these causes can help this research in devising solutions that meet the requirements of the issues and their causes.

CHAPTER 2: MUMBAI’S GEOGRAPHY, PLANNING HISTORY AND DEMOGRAPHICS

This chapter focuses on Mumbai’s geography, its planning history and its demographics. It thus provides a better understanding of what has given rise to the recurrent deluge in the city.

1. Physical Features

The Mumbai Metropolitan region is located in the tropical zone, on the west-coast of India. It is bordered on its three sides by sea: the Arabian Sea to the west and south and the Harbor Bay and the Thane Creek in the east. The Mumbai region covers an area of 600.71 square kilometers. An aerial view (Adjoining figure) of this region shows a tapering island, about 25 miles long and two to seven miles wide, connected to the region’s mainland towards the north-east and separated by an estuary. At present, “the region includes the original group of islands of Mumbai, and a large part of the island of Salsette. The Salsette-Mumbai island creek and the Thane Creek (Adjoining figure) together separate it from the mainland.”

The area is just about 10 to 15 meters above the region’s mean sea level, while at some locations the topographical elevation is barely over the level of the sea. The Backbay and Bandra reclamation are the two of largest parts of Mumbai, reclaimed from the Arabian Sea. The soil cover within Mumbai city is mostly sandy while it is largely alluvial in the suburbs. Until about a decade ago, the region has had a year around moderate climate, with the mean temperatures ranging from 75-90°F. On an average, it has had an annual rainfall ranging from 230-240 millimeters, which is one of the highest to be recorded in the entire country. As is the case with most of the islands around the world, this island region also consists of a central mountainous area. In Mumbai, this hilly consist of the Vihar Lake and Powai Lake that serve as reservoirs to store the rainwater. In the past, the excess rainwater from these reservoirs overflowed and drained through the city’s natural drain, the Mithi River, into the Mahim Creek and finally into the Arabian Sea.

2. Regional History
The history of the Mumbai region give details of the socio-economic factors that have led to the physical development of the city as it is in the present day. Since the advent of civilization, urbanization is related to proximity of water sources such as the sea, rivers and lakes. As Donald Geis and Barry Steeves mention in their article, “development along seacoasts and rivers has been a product of a logical evolution.” Access to a water-source is vital for transportation, economic development, defense, recreation, social amenities and sanitation. The strategic importance of each of these factors has changes with passing times. However their linkage and the need for each of these factors to be close to a water source, has persisted. Human settlements have taken advantage of the nature on both, economic and social front. The need for water has led to humans occupying low- lying lands that are prone to flooding. This has led to the rapid urbanization of these areas, as is the case of the metropolitan region of Mumbai, formerly known as Bombay. The city has proven to be the proverbial “melting pot” for people from various cultural, ethnic and economic backgrounds. With an advantage of being located next to the Arabian Sea, the region has fostered international trade in the past centuries. In the past, it became a favorite hub for various invaders including the Moguls, the Portuguese and the British among others.

In 1534, the Portuguese, who had by then acquired many important trading hubs along the west coast of India, forcibly took Bombay away from the Moguls. They also guarded this possession by constructing forts at Sion, Mahim and Bandra. Until the 1660s, Mumbai was made up of seven islands, comprising of Colaba, Mazagaon, Old Woman's Island, Wadala, Mahim, Parel, and Matunga-Sion; these islands were eventually connected in various phases, by reclaiming land from the sea. In 1668, Queen Victoria, the ruler of India leased out these islands to the English East India Company. The Company, which then operated from the port of Gujarat, a port to the north west of Bombay, was in search of a deeper port to facilitate the docking of larger vessels and it found the islands of Bombay apt for this use. The sea-routes at Worli, Mahim, and Mahalaxmi transformed the soil cover linking the islands into marshes and thus made Bombay, an extremely unsanitary place at that time. Many commuters traveling from one island to the other by boat lost their lives during the monsoon storms. To end this crisis, in the years 1784-1845, the seven islands were linked in phases by reclaiming land and connecting the various islands to form a network of roads. With the British invasion, also came the rapid development of the city’s transportation infrastructure. On the April 16, 1853 the first railway line of India, began operating for 21-miles, between Bombay's Victoria Terminus and Thane. The opening of the Suez Canal in the year 1869 brought the Western world closer to Bombay and the city prospered. Following the success of this venture, more projects were launched to reclaim more land and build more roads, rails and wharves.

3. Population Dynamics
Bombay started drawing fortune seekers by the thousands. The population of the city had risen from 13,726 in 1780 to an astonishing 644,405 in 1872, within a century. By 1906 the population of Bombay was as much as 977,822. The expansion of Mumbai continued until present times and the city has now developed into India’s financial capital. As India’s center of commerce, financial institutions like the, Bombay Stock Exchange, National Stock Exchange, Reserve Bank of India, and other major banks are housed here. It is also home to numerous refineries, power plants, residential and commercial developments and port facilities. Additionally, tourism is one of its important industries, especially along the coastal zone. With one of the world’s most promising economies, it witnesses a large influx of population every day. This influx comes from the neighboring cities, states and even from the neighboring countries, either legally or illegally. As of the 2001 Census, Mumbai had a population of about 16.37 million, which is expected to shoot up to 25 million by 2025 and surpass 35 million by 2031.The population density of this city also exceeds that of most of the other metropolitan cities in the world. Mumbai has a population density of 27209 persons/sq. km, compared to a figure of about 900 persons/sq. km, in Sydney, Australia. Adjoining figure shows the pattern of population growth, for the city of Mumbai and the Mumbai Metropolitan Region for the years 1971-2001, with projections for the years 2001-2031. The steep growth that is depicted in the accompanying graph demanded more space to be accommodated. This led to the destruction of the mangroves and extensive reclamation of land from the sea. A detailed analysis of these events is performed in the following section of this chapter, starting with a review of the city’s growth pattern and resultant history of its planning.

4. Growth Pattern and Planning History

The demand to house the overwhelming population growth has led to Mumbai reclaiming more land from the sea, rivers and marshy lands. Nariman Point; the city’s southern most tip, the whole of Marine Drive, large parts of Colaba, Oval Maidan and most of Ballard Estate have been reclaimed as the Backbay Reclamation. Low-lying areas like Haji Ali and Mahalaxmi, that were originally swamps, were also reclaimed under this scheme for development. A lot of this development is in the form of vulnerable, informal and often illegal settlements, such as the ones seen on the banks of Mithi River. “Nearly 65% of the city’s population is known to reside in illegal or informal settlements. According to the 1985 census, the city had nearly 2335 slum settlements, which has multiplied to almost five times that number in the past two decades or so.” The governing authorities have added to this plight by permitting development in the areas, which earlier served as natural drains for the city. This blocks the natural flow of water.

Even the city’s lake beds are not spared. The Mithi River is inundated because its course has been reduced to almost 1/3 of its original width due to the excessive reclamation of land. Infrastructure facilities such as the Bandra-Worli sea-link and the extension to the Santacruz International airport have been largely developed on this reclaimed land.Thus, the uncontrolled construction and concretization of land on either of its sides has left the Mithi River with no “flood-banks.” The Mumbai Metropolitan Regional Development Authority (MMRDA) has also been largely responsible for the reclamation along the Mithi River to facilitate the construction of the Bandra-Kurla Complex; a commercial hub in the city's northern suburbs, planned to dissolve the further concentration of offices and commercial activities in South Mumbai. It covers about 370 hectares# of low-lying land on either sides of the Mithi River, the Vakola and the Mahim Creek. The area has been massively reclaimed and concretized. The entire process has continued until the present day and the city now has the lowest ratio of open land available per person, compared to any major metropolis.

The city’s “Natural ‘sinks’ for the excess rainwater such as open grounds – with vegetation, forests, mangroves, marshes have been reclaimed and developed, and are therefore, now in short supply.” The Thane Creek has also witnessed some major, unchecked reclamation. At the local level, the region’s planning authorities have tried implementing the Coastal Regulation Zoning (CRZ), “which prevents development within 500 meters from the high tide line of the sea.” However, the developers pay no heed to this regulation and continue with their land-filling exercise.

Moreover, the faulty reports made by the state government’s environmental authority; the Center of Earth Sciences (CES), deleted various areas from the jurisdiction of the Coastal Regulation Zone (CRZ). The report legally permitted developers to develop rashly in the areas that fall in the coastal flood plains. The results of this report reflected in the Mumbai development plan 2005-2025. The plan relaxed the laws in CRZII and CRZIII (coastal zones which have been granted concessions for development depending upon the proposed land-use), in order to meet the extra demand for almost 15-20% more housing. These regulations should be reviewed again and updated to deal with the city’s current climatic conditions and the change in the amount of annual rainfall. The city’s rapid urbanization has also led to a fast reduction of the mangroves in the city. Figure 9 shows a graphical representation of the area-wise reduction of mangroves in the Mumbai Metropolitan region between the years 1925-1994.

Another alarming atrocity on the environment is the quarrying of the hills to make land available for the expansion of the city. Extensive, legal and illegal quarrying of the hills in and around Powai has made the hill remnants extremely unstable, making them highly vulnerable to collapse. The hill slopes have been cleared off vegetation to maximize the construction potential and this has added to the risk of landslides in this region.
In addition to a loss of the vegetation, quarrying also results in the destruction of the earth’s natural, permeable surface that has an innate capacity to retain and absorb the rain water.

5. Current Efforts to Save the Banks of Mithi River
There have also been certain measures taken up by the MMRDA to contain the alarming decrease in the natural sinks in the city. To make up to the natural drainage lost from the extensive reclamation of the Mithi River, the MMRDA has developed, what is now known as the Mahim Nature Park. Until about 30 years ago, this site was used as a dumping ground for the city’s garbage. Most of this garbage overflowed into the Mithi River, obstructing its natural flow. Towards the end of the 1970s, this area, stretching approximately over 37 acres in the Bandra-Kurla Complex, was ecologically reinstated, to be developed as a nature-friendly park by the MMRDA, in partnership with the WWF-India, an environmental conservation organization. Located on the southern bank of Mithi River (where the river flows into the Arabian Sea at the Mahim Bay as one of the major drainage outfalls of Mumbai), this small forest-like development can be described as a miracle of sorts. The park essentially serves as a green breather for a pollution-stricken city and a sanctuary for birds of various species and other rare insects. In addition, this park also serves as a natural sink with a permeable soil cover that absorbs excess rain water and drains the remainder of it into the bay.

However, the park covers only a small fraction of the area covered by the Bandra-Kurla Complex and is not sufficient to serve the entire city. This is because, in addition to the Mithi River, Mumbai largely depends on the storm water drainage system laid out throughout the region. A detailed layout, of the city’s drainage system and its contribution to the inundation of the city during the annual monsoons, is discussed in the following chapters.

CHAPTER 1: INTRODUCTION

Floods and storms are natural: a factor that must be stressed. The crisis arises when these floods take their toll on human life and property. The floods that swept over Mumbai in the monsoon of 2005 and more recently in 2009 in various parts of India, were the worst to be recorded in the city’s history of flooding. As far is Mumbai is concerned, the cause of this disaster was primarily the lack of sufficient drainage to help let out the floodwaters; this was further compounded by a high tide. The result was a city-wide inundation that battered the life and property in Mumbai. The event rendered the city dysfunctional by crippling its basic essential utilities and public means of transportation which are the lifelines of the city. This episode, that left a trail of massive destruction in Mumbai and its surrounding region in 2005, can be termed as a case of urban flash flooding. However, the probability of its recurrence in the future cannot be denied and this has been proven by the moderate floods that the city witnessed in the monsoon of the year 2006 as also by the ones that destroyed settlements in various parts of India, in 2009. The fact that global climate is changing largely contributes to this prospect of recurring floods. But, whether these floods would mainly result from continuous and heavy downpours bears some uncertainty in the view of the scientists who have been scrutinizing the world-wide change in climate patterns. Nevertheless, they believe that the global climate change may result in shorter but more intense monsoons in India. Likewise, these experts also claim that the melting of the ice caps at the poles and the vast reclamation of land from the sea, for the future expansion and urbanization of land, have substantially contributed to the rise in the sea-levels world-wide. Thus, in the event of a high tide or heavy rains or both, coastal areas such as Mumbai would be highly vulnerable to intense flooding, more often. It thus becomes inevitable for the governing and planning authorities of such coastal regions to include flood mitigation policies as an integral part of their general development framework.

Following the devastation left behind by the floods of 2005, the state government has been working towards minimizing the adverse effects of the floods by devising a flood mitigation framework for the city of Mumbai and its surrounding region. However, the destruction caused in the city by the moderate floods of 2006 is testimony to the fact that the flood mitigation mechanism, currently adopted by the city of Mumbai, is inefficient in curbing the intensity of the floods and their distressing consequences.

Therefore, this study makes an attempt to formulate and recommend policies from a planner’s point of view. The prime aim of these recommendations is to revise the existing flood mitigation structure of Mumbai as well as to suggest planning policies that can guide the future development of the city and curtail the adverse effects of the floods. At first, this study examined the probable causes for the intensity of the inundation in the city of Mumbai, after which it scrutinized the city’s presently deployed flood mitigation system to identify its shortcomings. Subsequently, this research conducted case studies to examine the role of planning in flood mitigation. In addition to an extensive review of Mumbai's history related to flood management, four additional regions are studied to reveal the success and failure of different mitigation strategies. These include New Orleans, Delaware, South Africa, and Bangladesh. Also, existing literature was examined in order to develop a comprehensive understanding of the best practices planners can utilize for proactive flood mitigation.

This report is organized as follows. An overview of Mumbai's geography, demographics, and planning history is discussed in Chapter 2. This is followed by an extensive analysis of the severe flooding in Mumbai in 2005 and 2006. Chapter 3 discusses the specific factors that influenced the severity of the flooding, including both natural and man-made causes. A review of the existing flood mitigation strategies in Mumbai is discussed in Chapter 5, while certain flood mitigation strategies not been addressed in the case-studies but crucial for the city of Mumbai are discussed in Chapter 6, through a review of literature about the best practices to manage floods. Based on this research, Chapter 7 recommends planning policies to mitigate the recurring inundation in Mumbai. The results of this research indicate that; The flood mitigation framework for Mumbai has to include planning policies suggesting more preventive measures as opposed to only post-flood relief measures. To achieve this, the policies should use sustainable development strategies as its basis to plan the future expansion of the city. Also, improving the existing infrastructure, to withstand floods, should constitute an essential part of the city’s flood management plans. Lastly, a proper co-ordination between the various flood management bodies is also essential to effectively implement the mitigation strategies as and when required.

While, this blog mainly discusses flood mitigation strategies for Mumbai region, the solutions are pretty much applicable to any flood affected region in the world.