Flooding is an accumulation of water in an area either by direct rainfall irresistible to the volume of drainage systems or a spill of huge amount of water from water bodies beyond normal limits. Urban floods in India has slowly started to become a regular phenomenon. Recent events of urban floods include 2013 Uttarakhand floods due to could burst and Kashmir deluge due to torrential rainfall; 2015, Chennai deluge;floods in Assam and Madhya Pradesh in 2016.
Causes:
Natural causes:
- Meteorological phenomenon : Cyclone like Nada, Roanu, Vardah making landfalls in coastal areas induce heavy rainfall finally leading to flooding.
- Excessive rainfall in some cases.
- Change in course of river: Eg: Kosiin Bihar
Man made causes:
- Encroachment:More migration >> reduced availability of land >> higher economic value of land >>> more encroachment of water bodies >> reduced economical services from water bodies. Charkop Lake in Maharashtra, Ousteri Lake in Puducherry, Deeporbeel in Guwahati are well known examples of encroachment.
- Pollution: Explosive increase in the urban population without corresponding expansion of civic facilities such as lack of adequate infrastructure for the disposal of waste results in waste clogging the natural channels and storm water drains. Thus flooding.
- Cultural or religious festivalsalso misuse water bodies.
- Illegal mining activities:Illegal mining for building material such as sand and quartzite both on the catchment and on the bed of the lake have extremely damaging impact on the water body. For example, the Jaisamand Lake in Jodhpur, once the only source of drinking water for the city, has been suffering from illegal mining.
- Interference in drainage system: drainage congestion caused by badly planned construction of bridges , roads , railway tracts, hampers the flow of water and the result is flood.
- Unplanned tourism activities:Using water bodies to attract tourists has become a threat to several urban lakes in India. Ashtamudi Lake in Kerala’s Kollam city that has become polluted because of spillage of oil from motor boats.
- Unplanned release of water from dams: Unplanned release of water from dams lead to floods. Eg:Case of Kota.; Unplanned release of water from Nepal has caused floods in Northern Bihar; Excessive damming on tributaries of Brahmaputra such as Xiabuquhas led to inundation of vast areas in Assam.
- Absence of administrative framework: The government does not have data on the total number of urban water bodies in the country. Few cities have recorded water bodies because of court rulings. Union Ministry of Environment & Climate Change had not identified wetlands and no identifications of risks to these wetlands due to pollution of river water. Central Pollution Control Board (CPCB) had not identified the major aquatic species, birds, plants and animals facing risks due to pollution of rivers and lake.
Way forward:
- Detailed survey of the wetlands and then bring every water body and its catchment under legal protection.
- Inclusion of water bodies and their catchment in the city development rules.
- Comprehensive urban planning with proper study of topography, drainage, rainfall, soil lithology with improved flood water disposal system
Floods in India are an outcome of both natural and anthropocentric changes. However the latter has been more responsible for floods in the current age of Anthropocene. Thus a comprehensive urban planning which reconciles both environment and economic needs is required.
