CHAPTER 6: RECOMMENDATIONS OF FLOOD MITGATION STRATEGIES FOR MUMBAI

        The heavy rains that have been inundating the city of Mumbai and it surrounding regions time and again during the monsoons every year indicate that the city is still short of a sound flood mitigation framework. The existing efforts by the city’s governing and planning authorities towards formulating flood alleviation strategies have only been marginally successful in fulfilling their purpose. Moreover, the national disaster management framework released in the year 2004 takes a holistic approach at managing and reducing disasters by suggesting general policies applicable to all the states in the country and not just the Mumbai region in particular. The framework also considers floods only as one of the many natural disasters that it suggests strategies for. It does not provide any flood-specific mitigation strategies so to speak of.

        The Chitale Committee appointed by the governing authorities of Mumbai, following the floods of 2005, does provide some mitigation strategies specific to flooding. However, these strategies have succeeded only partially in tackling the flooding in the following year. Thus, this study aims at suggesting improvements to the existing flood-mitigation framework of the city to minimize or if possible, completely avoid the destruction of life and property and the disruption of the normal functioning of the city which results from the floods. For this purpose, this study conducts case-studies of other flood stricken areas and refers other professional literature as a guideline to suggest additional flood mitigation strategies specific to the city and the region of Mumbai. The flood mitigation framework can be broadly classified into pre-event measures and post-disaster measures. In an approximate chronological order these are as follows:

1. Pre-flood Mitigation Measures:

a. Mitigation of floods:

- Data Collection and Analysis
- Vulnerability Reduction

b. Preparation for Floods 

-Prediction

- Emergency Preparedness (including monitoring, alerts)
- Education, Training and Awareness

2. Post-flood Mitigation Measures:

- Rescue and evacuation

- Relief

- Rehabilitation and Reconstruction

3. Role of Government and Private Sector in the flood mitigation framework

1.     Pre-flood measures:

     

      As is generally believed, prevention is always better than cure. Investing time, finance and efforts in the conceiving the pre-event flood mitigation strategies may considerably save efforts needed for post-event flood mitigation strategies. They may also reduce the destruction of life and property to a large extent.

1.1.     Limiting the floods and their after-effects:

Floods are a form of natural disaster that cannot be totally avoided. However, their intensity and their after effects can be considerably reduced by adopting the following actions.

1.1.1.     Data Collection and Analysis

Figure 1: Proposed zoning of flood prone areas as a flood mitigation strategy

      Under this plan of action, climatic data stating expected amount of rainfall is collected with the help of satellite images and this information is integrated into the geographic data demarcating the flood prone areas, using GIS.

This data will then be used by the planning authorities to reserve open spaces in the floodplains such as flood basins or wetlands for the water to accumulate in the event of floods and prevent urbanization of these areas by way of land-use and zoning regulations. Figure 1 shows a map with suggested zoning strategies of the flood prone areas of Mumbai to mitigate the effects of flood. The areas shaded in green are coastal zones, highly susceptible to inundation from high tides as well as heavy rains. They should thus be zoned as open recreational spaces that can act accumulation points for rain and flood waters. Residential, commercial and any kind of development that might have habitable spaces should be prohibited in these areas, as a part of this zoning. The development in the areas shaded in brown should be also be guided by building codes that reduce the vulnerability of the building occupants to the adverse effects of flooding as discussed in the following section.

        1.1.2.     Vulnerability Reduction

Figure 2: Building designs suggested as mandatory flood

 mitigation strategies in flood prone 

areas of Mumbai.

·         The building codes should include flood mitigation measures such as mandatory flood control devices, use of specific impervious building materials, specific building methodology to create water-tight enclosures and elevation of the habitable floors of a building above the expected level of flood. Figure 2 shows graphical representation of elevation levels of buildings suggested for flood prone areas of Mumbai. The blue portion depicts the mean flood level and the yellow portion shows the level of habitable spaces in the building. Such elevation should be mandated in flood prone areas demarcated in brown and green (if any) in the Figure 1. Other flood mitigation strategies that can be mandated in flood prone zones of Mumbai include designing buildings to regulate rain water for constructive use such as watering planters. Figure 3 shows how an impervious material covers the exterior of the building and is laid at a grade at its junction at ground level, such that the rain water flows down and is directed to the surrounding planters.

Figure 3: Flood-proofing in building design 

that can also be used to redirect storm water to irrigate plantations.

·                     The building codes should mandate alternative power supply such as generators as a standby in the event of the failure of the city’s main power lines.

The data generated by GIS can also be used to restore the natural eco-systems by way of reinstating the region’s natural flora and fauna. The reclaimed land around the Bandra Kurla complex along the bank of the Mithi River has been extensively concretized and has also reduced natural course of the river. However the opposite bank of Mithi River is occupied by slums and has been considered by the government for slum redevelopment program.  Considering the inundation of Mumbai during the years 2005 and 2006, the bank should be reserved as open space, with exposed natural soil that can serve as a seepage ground for flood water and can also restore natural ecosystems. This scheme would be an extension of the Mahim Nature Park that has been developed towards this cause.

Figure 4: Map showing reclaimed land on the Banks of Mithi River that should be reserved as an Ecological reserve

Figure 5: Map showing recommended

 locations for installation of levees. (In Black)

Figure 4 shows a map depicting the reclaimed land on the banks of Mithi River that can be restored as ecological reserve. This strategy will also solve the issue of subsidence, a phenomenon that usually occurs on reclaimed lands. Zoning the reclaimed lands as open recreational spaces will eliminate the vulnerability of future developments to subsidence.

·         Flood control devices that should be installed at particular locations in the flood prone areas are levees. These levees have to be constructed with strong, impermeable materials. Figure 5 shows specific areas in Mumbai wherein installation of levees can significantly reduce their susceptibility to floods. Areas such as the Thane Creek, the Mahim Creek and South-Eastern Coast of Mumbai are probable locations which need levees.

·         To facilitate the zoning of flood prone areas as open spaces and water reservoirs the government can exercise land-acquisition, compensatory regulations and transfer of development rights. Land acquisition gives the local governing authorities the right to acquire flood prone areas and have full control over their development in the pre- and post disaster period. Such acquisitions mainly depend on state funding.

      On the other hand compensatory regulations and transfer of development rights are special forms of land-acquisition which compensate land owners in exchange for the restrictions of use on their land. By practicing these rights the government can restrict development of floodplains and compensate the land-owners in these floodplains for the losses incurred from the loss or transfer of development rights.

·                     Maintenance of existing drainage and proper design of new drains can considerably reduce the extent of flooding in Mumbai. Some of the actions that can be taken to achieve this task are:

-Design closed drains which prevent them from collecting silt and garbage.

-Regularly clear the drains off the accumulated silt and sewage to facilitate the free flow of water, using modern day equipments. Scrap the water table.

-Create additional outfalls and pumping stations at critical flood-prone locations.

-Avoid settlements along existing open drains.

·         Relevant departments should be established by the state government to handle specific disasters such as floods.

·         Each department of the State Government should set apart an appropriate portion of funds under the plan for specific projects addressing vulnerability reduction and preparedness in the event of floods.

·         There should be a close interaction between the corporate sector, nongovernmental organizations and the media in the city wide efforts for flood prevention and vulnerability reduction.

·                     Lastly, one of the most effective pre-flood mitigation measures is to allow citizen participation and input in planning flood mitigation strategies to come up with the best possible solutions. Different strata of society, especially in Mumbai, show varied perceptions and relationships to natural hazards, and reflect different socio-economic and socio-psychological backgrounds. Thus, involving the general public in disaster mitigation decision-making processes may enable local authorities to develop hazard mitigation strategies that gel well with the local context and thus address the concerns and social expectations of different population subgroups.   

1.1.     Preparation for Floods 

         As mentioned earlier, floods may not be totally avoidable. However there are certain strategies that can be applied to prepare the flood prone areas to deal with the floods when they occur and prevent loss of life and property. Some of the strategies under this category are as follows:

1.1.1.     Prediction

     The meteorological department of Mumbai should use modern technology that can accurately forecast weather. Programs like GIS can be used to process satellite images to predict the weather changes. This can be relayed to the masses through a range media including television, newspapers, radio and internet.

1.1.2.     Emergency Preparedness

Emergency preparedness for floods broadly includes strategies such as monitoring and alerts;

·                     The process of gauging rainfall should be carried out using automatic rain gauges as opposed to the manually operated rain gauges currently used by the city. These rain gauges can be calibrated to relay alarm at predefined values of rainfall intensity. The data from the rain gauges will ultimately serve as warnings in case a possibility of flooding is detected.

Figure 6: Sensors in the installed in the levees

 to relay warnings at critical pressures

·               The levees should be armed with elaborate fiber-optic sensors (Figure 6) that detect the forces within the structure, so as to provide a prior warning of the critical pressures that could cause its damage or collapse.

·         Buildings such as local schools, in flood prone areas, which can be used as shelters for flood victims, should be essentially designed to provide with sufficient sanitation and other facilities to house the flood victims.

·         In areas, surrounding the flood-prone zones, flash floods are likely. These areas could be guarded from floods by use of in-place flood control devices such as water tight gates. Water tight enclosures should be mandated as a building code in all the future developments in the city.

·         Above all, there should be a well developed communication between all the departments of the  government responsible for flood mitigation and water management.

·        Civic amenities like pipelines carrying sewage and water should be planned away from each other and  constructed with flood resistant materials, to prevent contamination of clean water and the spread of epidemics.

·         The roads should be constructed out of flood-resistant materials that can withstand the wear and tear caused by heavy rains during the monsoons.

·         Restoration of slums should be avoided at all cost, especially along the banks of the city’s drainage outfalls, such as the Mithi River. Alternatively, the population of settlements along the banks of Mithi River should be relocated under the city’s Slum Redevelopment scheme to a safer location. This would prevent clogging the banks of the river and considerably reduce the extent of flooding of the area and its precincts.

1.1.3.     Education, training and awareness

·         Creating awareness amongst the masses about the floods and their mitigation strategies helps prevent panic and chaos.

·      Awareness should also be created to help harvest the excess rain water and use it for appropriate purposes

·         Citizens should be trained to operate the in-place flood control devices installed in the buildings they occupy. This would help protect themselves and their belongings, without much delay in the event of floods.

·         The government should mandate periodic safety drills to help citizens remain alert for any catastrophe and also to ensure proper functioning of the flood-mitigation equipments.

2.     Role of the Government and the Private Sector in the flood mitigation framework:

2.1. Role of the Government

      For pre-flood as well as post mitigation strategies, the Government should serve as a one point contact coordinating between various city agencies such as the weather bureau, the telephone department, other media such as radio and television, electricity department, civic amenities department, port authorities and roads department, as these departments as consortium are responsible for the normal functioning of the city.

        The Government should also formulate policy guidelines and institutionalize a suitable co-ordination mechanism between the various agencies including the ones mentioned above along with the city police department and rescue operations team that are concerned with the disaster management in real time.

      In fact, each level of government has a different role to play in the flood vulnerability reduction. Thus, it is essential that these roles be performed as a part of a coordinated strategy. Overlapping the functions and responsibilities many needlessly exhaust the resources and waste valuable time, thus weakening the resilience to the floods. In putting up an effective strategy against floods, each level of the government should have a definite understanding of its role and specific responsibilities within the overall structure of the flood mitigation framework. For this purpose, adequate resources need to be made available and key responsibilities of the government in this regard include:

• Defining an institutional framework with the participation of local, regional, and national and even international entities such as various relief organizations;
• Strengthening the monitoring systems for climate change and floods, while institutionalizing the warning mechanisms;
• Decentralizing the decision-making process to the local level to ensure prompt action, transferring financial resources and enhancing the technical expertise of the flood mitigation team.

2.2. The Role of the Private Sector:

        Depending upon the degree of the economic activity in which the private organizations are involved and the amount of revenue generated by these activities, the organizations should have different incentives to engage in vulnerability management. Their strategies must integrate the expertise developed to handle hazards into vulnerability management and should foster productive activities as part of the reconstruction efforts. The institutional and legal framework should provide comprehensive regulations whereby private agents find it in their best interest to be actively involved in the vulnerability management.

    As is evident from this chapter, it takes a perfect synchronization between the various levels of the city’s government, the planning authorities and various sections of the civil society as well as a proper harmonization within these bodies to build up a sound flood mitigation mechanism for the city of Mumbai. Their coordination is critical at various stages of the flood management process, including the stage prior to the floods, during the floods and after their occurrence.

    Adopting this framework, essentially in that order can ensure reduction in the intensity of the inundation that disrupts the life and working of the city of Mumbai every year during the monsoons. Likewise it would also help conserve this water and help prevent the droughts that plague the state each year; a fact that seems like a paradox in the city that receives such a heavy downpour.

CHAPTER 5: EXISTING FLOOD MITIGATION STRATEGIES FOR MUMBAI

Flooding in the monsoons has been a common phenomenon in Mumbai. To deal with this annual event, the city’s disaster management framework includes some mitigation measures drafted out by the city’s planning commission and Municipal Corporation. The chapter looks at these measures and analyzes their shortcomings with respect to the intensity of the inundation faced by the city in the recent years.

1. Existing Flood Management Framework of Mumbai

Providing relief measures in the event of natural catastrophes such as floods has since long been one of the main goals of the disaster management department of the Mumbai Metropolitan Region as well as other states in India. The Central Government of the country, however, associates itself only with post-disaster relief measures and its response is determined by factors such as: “(i) the gravity of the disaster in question, (ii) the scale of the relief operation required and (iii) the requirements of assistance from the central government to expand the financial resources at the disposal of the State Government.” So far, the disaster management framework has been drafted for the country as a whole by the Central government of India. It consists of flood mitigation strategies as a part of its plan to deal with other natural and human induced disasters such as fires and earthquakes. The following report drafted in 2004 provides broad guidelines to exercise mitigation strategies for various kinds of disasters:

1.1. Disaster Management of India Report( 2004):

The following status report of the Disaster Management in India (2004) lists the salient features of the draft national policy on disaster management:

• The report adopts a realistic and holistic approach towards the management of various calamities.


• Every “department of the Central/State Government should set apart an appropriate portion of its funds, for specific projects tackling vulnerability reduction and preparedness” in the event of a disaster.
  
• Where a number of projects have been lined up for an approval from the government, the projects incorporating mitigation measures, in their plans, should be given priority over the other projects to be approved. These strategies should be integrated into the Government’s current mitigation programs.


• In order to be approved, each project in a disaster prone area should have disaster mitigation as an essential condition to be fulfilled. The project report should include a testimonial stating as to how the project tackles the issue of incorporating mitigation strategies into its design.


• Involvement of the general public and generation of awareness amongst the masses, essentially the susceptible sections of the population, should be stressed as an essential step towards sustainable vulnerability reduction. This is a vital part of the disaster management structure since the general public is the first responder to various calamities. Therefore, unless it is given authority and “made capable of managing disasters, any amount of external support cannot lead to optimal results.”


• A close interaction should be established between the “corporate sector, non-governmental organizations and the media,” in the city wide “efforts for flood prevention and disaster risk reduction.”


• Institutional framework with the right sequence of command should be developed to regularize the mitigation process. Also, the disaster managers at different levels of the government should be appropriately “trained to ensure a coordinated and quick response at all levels.”


• Additionally, during the emergencies, arrangements should be made to share resources such as power, food and funds amongst the states.


• A tradition of “planning and preparedness” is to be integrated into all sections of the government to build up their efficiency to deal with the disasters.


• “Relevant government departments should be established for handling specific disasters.”


• “The design of all the new constructions must comply with the relevant Indian standards.”


• All the vital buildings in flood prone zones such as hospitals, railway stations, airports/airport control towers, fire station buildings, bus stands and administrative centers should be checked for the extent of their susceptibility to disasters. If necessary, they should be strengthened or remodeled to deal with the expected disasters in the future.


• “The existing relief codes in various states of the country should be revised to be developed into disaster management codes and manuals.” This would regularize the “planning process with a particular emphasis on mitigation and preparedness.”


• The Government should extend co-operation with the other nations that are proficient in the fields of disaster response, preparedness and mitigation. The resultant mitigation measures should comply with the strategic objectives of the country.

It is observed, however, that the policies drafted in this report provide a general framework for all kinds of disasters for the entire country.Therefore, following the destruction left behind by city’s deluge in 2005; Mumbai’s governing authority appointed the Chitale committee. This committee formulated flood mitigation strategies specifically for the city of Mumbai and its surrounding region.

1.2. Chitale Committee Report:

The Chitale Committee’s recommendations to mitigate floods in Mumbai can be summed up as follows:

• Create Contour maps of all the water sheds in the region using tools such as GIS.


• “Stream Gauge the measurement of flow (1 for 200000 populations)–This should be based on the catchment area.”


• Install Automatic Rain Gauges: This would prove to be much more efficient in serving the purpose as opposed to the existing manual rain gauges currently deployed by the city, to measure the rainfall (Adjoining Figure).

Maintain Storm Water network –Clean the debris from the existing storm-water drains, remove obstructions, rehabilitate SWD and ban the use of plastic bags that usually block most of the drains in the city (Adjoining Figure).

• Cover the trenches carrying water pipes, drain pipes and electric cables before the advent of monsoon; this would prevent unwanted accumulation of rainwater.


• Plan additional covered outfalls for rainwater and install additional pumping stations at critical flood prone locations.


• Similarly, create more holding ponds and reservoirs to accumulate the rain water and regulate this water towards constructive use such as generation of power and irrigation of agricultural lands.


• Review and revise the earlier disaster management reports and make them adaptive to the current social, economic and climatic scenario of the city of Mumbai.

These policies would still prove to be insufficient, considering the causes of the floods in Mumbai and their consequences, stated in the previous chapters of the study. What is truly required is a flood management framework derived from a reference of the flood mitigation and management strategies successfully implemented in other regions and countries. Regions facing the issue of recurrent flooding have been essentially been chosen for the purpose of this review.

Thus, in the next chapter, this study conducts case studies of the best flood mitigation practices that have applied in other flood-prone regions around the world. These strategies shall eventually be used as guidelines to formulate and recommend mitigation policies pertaining solely to floods and particularly for the Mumbai Metropolitan region.

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.