Flood Management

[keerthi sureshbabu]

Impact of Climate change on flood sector has reviews such as

•  mapping flood prone areas using modern technologies like remote sensing, satellite data and air borne laser terrain mapping.
• flood plain zoning bill be adopted and enforced
• flood hazad zonation maps be prepared and widely publised
• flood forecasting and warning network be strengthened and modernised
• instrumentation for monitoring of glacial lakes and warning for outburst flood be mandatory to appropriate organization and necessary institutional arrangement be set up.
• special studies and mitigative measures for landslide events shold be undertaken

[Sandeep Shukla]

REMOTE SENSING AND GIS APPLICATIONS FOR FLOOD

AND RIVER MIIGRATION STUDIES

 

INTRODUCTION

A flood is an unusually high stage in a river- normally the level at which the river overflows its banks and inundates the adjoining area. The damage caused by floods in terms of loss of life, property and economic loss due to disruption of economic activity are all too well known. Floods cannot be controlled totally, however flood damages can be minimised by proper flood control measures. Human activity tends to concentrate in flood-liable areas, which are often convenient and attractive locations for settlement and other economic endeavors resulting in greater flood damages. With an increase in population every year, more and more flood-prone areas are occupied for residential, agricultural and industrial activities.  Areas that under normal conditions were used for floodwater storage have become build up areas without any scope for flood water storage.  This has not only lead to frequent flooding of these areas, but also possibility of large scale economic damage along with the loss of human life, in case of a flood disaster.

With the development of remote sensing and computer analysis techniques, now traditional sources can be supplemented with these new methods of acquiring quantitative and qualitative flood hazard information. This static approach uses indicators of flood susceptibility to assess an area's flood proneness (Sellers et al, 1978). Both of these approaches are discussed below.

Remote Sensing Techniques for Floodplain Mapping

          Remote sensing technology can be especially useful and desirable when applied during the planning process. With remote sensing methods, the extent of floodplains and flood-prone areas can be approximated at small to intermediate map scales (up to 1:50,000) over the entire river basins. Flood hazard maps can be prepared early in a development planning study to aid in defining and selecting mitigation measures for proposed sectoral development projects. In addition to discerning the risks of flooding, the same satellite data can be used to assess other hydrologic and atmospheric hazards as well as geologic and technological hazards. Furthermore, this satellite information can provide natural resource and land-use information at a small incremental cost once the basic data are acquired. It must be emphasized, however, that remote sensing technology is a tool, one of many that are employed by planners today. Application of this technology does not solve problems, but it can provide a planning study with recent, historical, and repetitive information.

            Remote sensing can provide information on flood-inundated areas for different magnitudes of floods so that the extent of flooding can be related to the flood magnitude.  Duration of flooding can be estimated in view of multiple coverage of the same area within 2/3 days by satellites. High-resolution satellite data provides information on the floodplain and details of flood control works.  Inundation extent for specific flood return periods can be estimated.  Using close contour information inundation extent for given level elevation can be estimated which is a vital input for risk zone mapping.

Continuous availability of satellite-based remote sensing data in India has made understanding of dynamics of flood events much easier. The advantage of satellite remote sensing (SRS) technique is that, it provides a wide area synoptic coverage, repetivity and consistency, which enables the collection of information on all major flood events on a reliable basis. Satellite based remote sensing of the flood-plains aided with modern analytical tools like digital image analysis and Geographic Information System (GIS) provides capability to survey and monitor the ground situation and helps in planning flood management measures and assessment of flood dam