application of remote sensing and gis for flood risk analysis: a case ...

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IRJC International Journal of Social Science & Interdisciplinary Research Vol.1 Issue 11, November 2012, ISSN 2277 3630 Public attention. Inundations in Mumbai in July 2005, Surat in August 2006, Bihar in August 2008 due to breach in Kosi embankments, Karnataka in October 2009 are some of the flood events in the recent past that have resulted in considerable discussion in the public space. Every major flood event is immediately followed by a flood of a different kind – „scholarly‟ articles analyzing the flood event and the current flood management paradigm. Almost all such articles say more or less the same thing. some studies says the flood is described as man-made, the technology based flood management paradigm is declared as all wrong, the technocrats are admonished for thinking that they can concur the nature and finally, it is asserted that our ancestors had mastered the art of living with floods, which we should also adopt. As flood dynamics are more complex understanding flood management requires study of hydrology, open channel hydraulics, and river morphology. Amongst those who comment on flood Management studied on floods have found some solution for efficient flood management and mitigate flood along with further studies on lakes and rivers have symbiotic relationship in term of exchange of water inflow and outflow. 3 However Reliable and precise estimation of floods is critical for efficient flood management and surface water planning. Hydrologists use catchment and hydrological data to establish regional relationships between mean annual flood and various catchment and rainfall characteristics. The relationship is used for predicting floods of different return periods. Historically many human settlements were along the rivers but people chose the highest possible points thus minimizing chance of floods. But with increasing population of the cities, settlements had to occur at lower and lower levels and closer to river thus increasing chances for floods. This had happened in many Indian settlements. At the time when dam was built perhaps rivers had good carrying capacity and later on downstream as settlement encroaches the river catchments and their natural watercourses have caused flood.(5th WSEAS Int. Conf. on environment, ecosystems and development, (2007)). Floods are a naturally occurring hazard that becomes disasters when they affect human settlements. The magnitude and frequency of floods is often increased as a result of the following human actions. Settlement on flood plains contributes to flooding disasters by endangering humans and their assets. However, the economic benefits of living on a floodplain outweigh the dangers for some communities. Pressures from population growth and shortages of land also promote settlement on floodplains. Floodplain development can also alter water channels, which if not well planned can contribute to floods. Urbanization also contributes to urban flooding in four major ways. 1. Roads and buildings cover the land, 2. Preventing infiltration so that runoff forms Artificial streams. 3. The network of drains in urban areas may deliver water and fill natural channels more rapidly than naturally occurring drainage, or may be insufficient and overflow. 53
IRJC International Journal of Social Science & Interdisciplinary Research Vol.1 Issue 11, November 2012, ISSN 2277 3630 4. Natural or artificial channels may become constricted due to debris, or obstructed by river facilities, impeding drainage and overflowing the catchment areas. Deforestation and removal of root systems increases runoff. Subsequent erosion causes sedimentation in river channels, which decreases their capacity intern causes flood during rainy season. Failure to maintain or manage drainage systems, dams, and levee bank protection in vulnerable areas also contributes to flooding. The flash flood common in many regions results from the outbreak of dammed lakes. These dammed lakes can break resulting in flash flood. Hundreds of lives and millions of rupees worth of property and investment in high-cost infrastructure are lost in the region every year due to landslides, debris flows, and floods, along with the destruction of scarce agricultural lands. In the last decade floods killed many persons and affected billion people worldwide. And the number of events as well as deaths is increasing significantly higher in Asia than elsewhere, and among all water-induced disasters this number is much higher for flash floods . The Government of India (GOI) has been spending large amount of money on flood control, its main focus is on irrigation. GOI has launched „National Flood Control Program‟ in 1954 and set up the “Rashtriya Barh Ayog” (RBA), “National Flood Commission”, in 1976 to evolve a coordinated, integrated and scientific approach to the flood control problems in the country and to draw out a national plan fixing priorities for implementation in the future. The RBA in its report in 1980 identified flood prone districts in many states of India including Karnataka and also extended services by proposing strategies to mitigate impact of flood. It is interesting to note that despite of these efforts, India is still repeatedly witnessing massive flood hazards Under the concepts of integrated development many dams were built. Dams in India and anywhere else are made for different purposes including power generation, irrigation, flood prevention, land reclamation, and water diversion. Given the multiple objectives of dams, dam management and food control involves different stakeholders with different interests and responsibilities, but these efforts makes the flood control related decision making a complex process. This has become a quite common phenomenon in every states of India, including Karnataka which has been no exception as far as sufferings inflicted by natural and man-made hazards are concerned. The state has been frequented by cyclones, floods, droughts, landslides, subsidence and occasional earthquakes. Progressive trends of any region are controlled to a large extent by the requirements of the inhabitants, agriculture, industries, transportation, communication, education and Culture, which generally form the vulnerability attributes. Because of the high population density and concentration of industrial and agricultural activities across Karnataka, risk or vulnerability to natural or man-made disasters is particularly high. With increasing developmental activities in high-hazard zones, e.g. the coastal regions, the vulnerability scenario appears to be worsening with time. But recently flood caused in the north Karnataka region have attracted the professionals on the cause of flood and flood victims. The devastating floods of 2009 in Karnataka almost swept away 13 Districts. These floods created havoc in this affected region, resulting in immense destruction of human life, property and crops. 54
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