Wednesday, July 25, 2012

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.















9 comments:

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  3. Thank you so much for your response...just boosts me up to keep going!!!! I really wish to make a dent in the current system.

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  4. Hi, really like your blog. Wanted to know what the references are for the maps with original course of mithi and the reclamation in bandra kurla complex.

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  5. Hello Priti,

    I am very impressed with this work on Mumbai-
    I discovered it while searching on info for flooding and water management in Mumbai- I work for an engineering consultancy in England, but I love India and am passionate about seeing cities like Mumbai flourish with a greater certainty of water supply, reduction of pollution and mitigation against severe flooding.

    What is the latest on the developments in Mumbai?
    I have a research bursary which can be used for looking at resiliance in cities: is there anything you would like further research on? We do a lot of work with modelling sewer networks, flood risk and mitigation. Also we are involved with risk based prioritisation and contingency planning.

    I would love to talk more about these challenges- please contact me on
    david.w.burgess@gmail.com

    Best Regards
    David

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