Vulnerability Atlas of India by BMTPC: Unique Tool For Disaster Management
Introduction
As per prevalent geo-climatic conditions, the Indian sub-continent is prone to natural hazards such as earthquakes, windstorms, cyclones, landslides, floods, and thunderstorms. In fact, India has witnessed such disasters that lead a trail of destruction and which bring irreparable loss to lives and properties.
Recognizing the vulnerability of the Indian sub-continent, the Disaster Management Act was enacted in 2005, followed up by National Policy for Disaster Management in 2009, and the National Disaster Management Plan in 2016. Internationally, 1990-2000 was declared as the International Decade for Natural Disaster Reduction (IDNDR) by the UN General Assembly, which was subsequently supported by Yokohama Strategy for Safer World in 1994, Hygo Framework for Action (2005-2015), and the Sendai Framework for Disaster Risk Reduction in 2015-2030. All these policy frameworks brought a paradigm shift in disaster risk management from post disaster relief centric measures to pro-active pre-disaster preventive measures.
As per the National Disaster Management Authority (NDMA) report, about 58.6% land area of India is vulnerable to earthquakes of moderate to very high intensity; about 12% of land (over 40 million Ha) is prone to floods and river erosion; 5700 km of coastline, out of 7516 km long coastline, is prone to cyclones, wind storm surges and tsunamis; 68% of cultivable area is vulnerable to drought, and hilly areas are at risk of landslides and avalanches.
Though one cannot do much to prevent natural hazards, it is the man made habitats that pose much danger to life and property. This is aggravated by the exponential rise in population, increasing urbanization, and hackneyed construction practices. It is estimated that about 1.2 to 1.5 million houses get damaged by a single disaster every year.
We need to recognize the risks to housing and infrastructure and take timely preventive measures in future constructions. Under the umbrella of Ministry of Housing and Urban Affairs, Govt. of India, BMTPC brought out the Vulnerability Atlas of India, which, till date, is the only document on damage risk to housing stock in India w.r.t. natural hazards. The Atlas was first published in 1997, and the second edition (in 2006) was based on the 2001 Census data. The third edition is based on the 2011 Census data; it was brought out in 2019 and includes hazard maps of earthquakes, wind/cyclones, floods, landslides, thunderstorms and vulnerability risk tables based on the latest data. Its aim is to help bring greater preparedness in state governments and agencies in mitigating natural disasters. The Atlas is a useful tool not only for the public but also for urban managers and national and state authorities dealing with disaster mitigation and management.
Vulnerability Atlas of India Introduction
Vulnerability Atlas of India, 1997
BMTPC in 1997 brought out the ‘first of its kind’ Vulnerability Atlas of India covering the entire country with respect to earthquakes, cyclones and floods. The Atlas contains State and UT-wise hazard maps showing the degree of vulnerability right up to the district levels and district-wise tables of housing stock, indicating the risk against the forces of natural hazards which may strike in a particular region. Nearly 80% of the housing stock in the country comes under the non-engineered category, thereby leading to a much higher risk of damage and destruction due to earthquakes, cyclones, floods, landslides, etc.
The Vulnerability Atlas of India has been a benchmark contribution of BMTPC and has been commended nationally and internationally as the first example of its kind in the world. The International Jury set up by IDNDR Secretariat ranked this work of BMTPC in the 4th position out of 41 international projects of such kind. The Vulnerability Atlas of India was also recognized as GOOD PRACTICE amongst the cases received for Best Practices by the UN-HABITAT under the Dubai International Awards for the year 2006.
Vulnerability Atlas of India, 2006
With increasing emphasis by the Central Government on pro-active, preventive and mitigation measures by all States and Union Territories (UTs), availability of the latest information on hazards and vulnerability in a user-friendly manner has become a necessity. Since the publication of the Vulnerability Atlas in 1997, the hazard scenario, especially with respect to earthquakes and floods, has undergone changes. At the same time, more information is available on seismo-tectonic aspects in the country, tsunami effect of earthquakes, storm surges, rainfall data, and landslides. The housing scenario has also changed and the latest information is available through Census 2001. Politically also, new States were formed, and a number of districts were created. In view of all this, the BMTPC, under the guidance of the Ministry of Housing and Urban Poverty Alleviation, Government of India, was entrusted the task of revising the Atlas of 1997 through a Peer Group.
Accordingly, the second edition of the Vulnerability Atlas of India was brought out by BMTPC in 2006 based on Census 2001 data using GIS tools and digitized maps were developed for the first time providing hazard and seismo-tectonic information up to the district level. Based on Census Housing Stock data, housing risk tables up to the districts were also published, based on distribution of houses by predominant materials of roofs and walls.
Vulnerability Atlas of India, 2019
Since the publication of Vulnerability Atlas of India in 2006, there has been invaluable feedback from users on the Atlas. The Atlas was also brought out in a digitized CD form in 2008 and uploaded on the National Informatics Centre (NIC) platform. The National Institute of Disaster Management (NIDM), Government of India, also used the Atlas for training SAARC countries so as to prepare the region towards disaster risk reduction.
There have been some changes made in the information on disaster mitigation and management. New data sets with respect to earthquake occurrence, cyclones, windstorms, landslides, thunderstorm etc, have been brought out by nodal government agencies. There are demographic changes also on account of the formation of new states and new districts. During this period, the country also experienced some damaging earthquakes, cyclones, landslides, thunderstorms, urban flooding, and flash floods, all of which have caused significant damage to life and property.
BMTPC brought out the third edition of the Vulnerability Atlas of India based on 2011 Census data in 2019; it includes hazard maps of earthquakes, wind/cyclones, floods, landslides, thunderstorms and vulnerability risk tables based on the latest data. The Hon'ble Prime Minister of India, released the digital version of the 3rd edition on the occasion of the Global Housing Technology Challenge - India (GHTC-India), Construction Technology India 2019 Expo-cum-Conference, organized by the Ministry of Housing & Urban Affairs on 2 March 2019, at New Delhi. The Hon’ble Prime Minister, while releasing the Atlas, emphasized the need to formulate and implement various schemes of the Central & State Governments keeping in view the vulnerability of the region and the indicative risk assessment as given in the Atlas, and suggested that suitable provisions should also be included in the tender documents. The digital version is available at https://vai.bmtpc.org for wider access by various stakeholders.
Hazard Maps
The monitoring of hazards in the country is being carried out by (a) seismic occurrence and cyclone hazard monitoring by IMD and (b) flood monitoring by the CWC. In addition, noteworthy contributions are made by the Geological Survey of India in mapping the seismic and landslide prone areas, and by the Department of Earthquake Engineering, IIT Roorkee (DEQ), on all aspects of engineering concerning seismic risks. It is pertinent to mention here that the Bureau of Indian Standards Committees on Earthquake Engineering and Wind Engineering has already prepared a Seismic Zoning Map and a Wind Velocity Map, including cyclonic winds, and the Central Water Commission has prepared a Flood Atlas of India. BMTPC has also published a Landslide Hazard Zonation Atlas of India.
BMTPC used these hazard maps to prepare 1:2 million scale maps by superimposing the above available data on the Survey of India map of this scale as the base map. The earthquake, windstorm and flood hazard maps are drawn for each State and Union Territory separately, in which the various district boundaries are clearly shown for easy identification of the hazard risk prone areas. The seismic zones of India, based on intensities of earthquakes on MSK scale, and the intensity of wind hazards related with wind speed, are shown on the maps, identifying the various intensity zones.
Earthquake Hazard Maps
The Indian subcontinent has a history of recurrent occurrence of earthquakes with moderate to high intensities. The latest version of seismic zoning map of India as given in IS 1893 (Part 1): 2002 assigns four levels of seismicity for India in terms of zone factors. In other words, the earthquake zoning map of India divides India into 4 seismic zones (Zones II, III, IV and V). According to the present zoning map, Zone V expects the highest level of seismicity whereas Zone II is associated with the lowest level of seismicity. The general basis of the zones as deliberated in the code is:
Zone V: Covers the areas liable to seismic intensity IX and above on MSK (1964) Intensity Scale. This is the most severe seismic zone and is referred here as Very High Damage Risk Zone.
Zone IV: Gives the area liable to MSK VIII. This zone is second in severity to zone V. This is referred here as High Damage Risk Zone.
Zone III: The associated intensity is MSK VII. This is termed here as Moderate Damage Risk Zone.
Zone II: The probable intensity is MSK VI or less. This zone is referred to as Low Damage Risk Zone.
The Earthquake Hazard Map of India, States and Union Territories includes the seismic zonation of India, faults and thrusts, epicenters of earthquakes from IMD besides giving administrative boundary of States and districts (Fig.1).
Wind/Cyclone Hazard Maps
The country level as well as state-wise wind hazard maps contain the following information:
Basic Wind Speed Zones: The macro-level wind speed zones of India have been formulated and published in IS 875 (Part 3):1987 entitled “Indian Standard Code of Practice for Design Loads (other than earthquakes) for Buildings and Structures, Part 3 Wind Loads”. There are six basic wind speeds Vb considered for zoning, namely 55, 50, 47, 44, 39 and 33 m/s. From wind damage view point, these could be described as follows:
55 m/s (198 km/h) - Very High Damage Risk Zone - A
50 m/s (180 km/h) - Very High Damage Risk Zone - B
47 m/s (169.2 km/h) - High Damage Risk Zone
44 m/s (158.4 km/h) - Moderate Damage Risk Zone - A
39 m/s (140.4 km/h) - Moderate Damage Risk Zone - B
33 m/s (118.8 km/h) - Low Damage Risk Zone
The basic wind-speed zones are plotted in state-wise maps which show the district boundaries as well as the district towns for their easy identification. The Wind Hazard Map of India is given in Fig.2.
Flood Hazard Maps
The flood hazard maps (Fig.3) in the Vulnerability Atlas are based on the Flood Atlas of India (1987), and updated flood prone areas of Assam and other neighbouring States, include Bihar, West Bengal, and Eastern Uttar Pradesh included in the Task Force Report (2004). These maps mark the areas which are liable to flooding. Since these maps also show the district boundaries and the location of the district towns along with the rivers, district-wise identification of the vulnerable areas will be easy. As regards the latest data on flood prone areas, the scientific assessment of flood prone areas in India is under progress by CWC. The existing flood maps presented here are of 2006 Atlas and can be updated as and when the data is made available by CWC.
Landslide Incidence Maps
In the third edition of the Vulnerability Atlas of India, 9883 nos. historic landslide data, that have been mapped and field validated till 2016 by the Geological Survey of India (the nodal department of landslide studies in India), are incorporated to depict the landslide vulnerability of the various states of India. The distribution of such historic landslide incidences indirectly shows the relative densities of landslides in different landslide prone states in the map as well as in the associated textural database, indicating their type of movement, material type and dimensions, and in some cases their initiation years and damage details, wherever such information is available.
However, landslide incidences demonstrated in the Vulnerability Atlas (Fig.4) are time-dependent and dynamic, therefore, many cases of smaller landslides cannot always be recognized because of land use and vegetation changes over time. Besides, in the Landslide Incidence Map, the annual state rainfall as provided by IMD has also been shown.
Thunderstorm Incidence Map
Thunderstorm is a severe weather phenomenon, the impact of which is felt by all the sectors of society including aviation services. In general, the orographically dominant regions as well as the coastal areas are more prone to thunderstorm-based activities. In the Indian scenario, the most thunderstorm prone areas are the north-eastern states and the adjoining east India. Thunderstorms are also known as ‘Nor’westers’ because most of them move from the northwest to the southeast over these regions. Frequency of thunderstorms is the maximum during the pre-monsoon season (April-May), and are accompanied with lightning, squalls and sometimes heavy rain and hailstorms. Map showing the number of thunderstorms at a station during 1981-2010 is presented in Fig.5.
State-Wise Maps
State-wise maps of various hazards such as Earthquake Hazard Maps of Gujarat (Fig.6), Wind Hazard Map of Odisha (Fig.7), Flood Hazard Map of Bihar (Fig.8), and Landslide Map of Uttarakhand (Fig.9) are given here.
Vulnerability and Risk Assessment
It is noted that preliminary effort toward vulnerability assessment of buildings under seismic and cyclone intensities has been made by the Deptt. of Earthquake Engineering, Indian Institute of Technology, Roorkee and Structural Engineering Research Centre (SERC), Chennai, respectively. Taking guidance from this work, the types of housing as existing in each district has been taken from the Census of India, 2011 and categorised as per their vulnerability.
The vulnerability of the housing types to various intensities of hazards including floods, was estimated based on knowledge gained in past disaster damage surveys. The damage risk in each district is presented in a separate table, wherein the area of the district prone to various hazard intensities has also been shown.
The distribution of houses based on predominant materials of roof and walls over the whole of India according to 2011 Census is shown in Table-1. From the point of view of vulnerability to earthquakes, winds, or floods, it was seen that the type of flooring had hardly any significance, hence, was omitted from consideration, and that the roof types and wall types could not be grouped together. The appropriate grouping for the whole of India is shown in Table-2, wherein the wall and roofing groups are categorized as follows:
With these groupings, the vulnerability of each subgroup could be defined separately for any given intensity of earthquake, wind or flood hazard. The risk levels of the various categories of houses for the three hazards are shown in Table-3.
Epilogue
The Vulnerability Atlas of India is a unique tool to understand the overall hazard scenario and risk to the existing building stock for earthquake, wind, cyclone, and flood at the macro-level. No other such document is available for projecting risks to existing building stocks till date. However, for better preparedness of natural hazards and their mitigation, studies at the micro level are also required. There have been a number of studies by academic and other research institutions, but there will be a long way to go before the hazard and risk maps at the micro level are published officially for public use.
References
- Vulnerability Atlas of India, 3rd Edition, Building Materials & Technology Promotion Council, Ministry of Housing & Urban Affairs, Govt. of India, 2019.
- Vulnerability Atlas of India, 2nd Edition, Building Materials & Technology Promotion Council, Ministry of Housing & Urban Poverty Alleviation, Govt. of India, 2006.
- Vulnerability Atlas of India, 1st Edition, Building Materials & Technology Promotion Council, Ministry of Housing & Urban Poverty Alleviation, Govt. of India, 1997.
- “Census of India 2011” - Distribution of Census Houses by Predominant Material of roof, wall and floor of Census Houses.
- “Flood Atlas of India”, Central Water Commission, Ministry of Water Resources, Govt. of India, April 1987.
- “IS 1893 (Part 1):1984/2002/2016, Indian Standard Criteria for Earthquake Resistant Design of Structures, – Part 1: General Provisions and Buildings, Bureau of Indian Standards, New Delhi.
- “IS 875(Part 3):1987, Indian Standard Code of Practice for Design Loads (other than Earthquake) for Buildings and Structures, Part 3, Wind Loads”, Bureau of Indian Standards, New Delhi, Feb, 1989.
- IS 15498:2004, Guidelines for Improving the Cyclonic Resistance of Low Rise Houses and Other Buildings/Structures, Bureau of Indian Standards, New Delhi, 2004.
- IS 15499:2004, Guidelines for Survey of Housing and Building Typology in Cyclone Prone Areas for Assessment of Vulnerability of Regions and Post-Cyclone Damage Estimation, Bureau of Indian Standards, New Delhi, 2004.
- Report of the Task Force constituted to examine the causes of the problems of recurring floods and 22. erosion in Assam and other neighboring States as well as Bihar, West Bengal and Eastern Uttar Pradesh, Ministry of Water Resources, Government of India, 2004
- Agrawal Shailesh Kr., Kumar Dalip: Recent Trends in Disaster Mitigation & Management: Vulnerability Atlas of India. In: Sharma M.L., Shrikhande Manish (eds.) Advances in Indian Earthquake Engineering and Seismology – Contributions in Honour of Jai Krishna, pp. 383–410. Springer (2018).
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