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Impact of Flood Dynamics on Eastern Gangetic Agroecosystem: A Remote Sensing Analysis
Rabi N Sahoo
Scientist (Sr Scale)
Indian Agricultural Research Institute,
India
Email: rnsahoo@yahoo.com
IPABROL
Director
Centre for Advancement of Sustainable Agriculture
Email: iabrol@vsnl.com
Raj K Gupta
Head and Regional Facilitator
CIMMYT India (RWC)
r.gupta@cgiar.org
'Flooding is a natural and recurring event for a river or stream which is a result of heavy or continuous rainfall exceeding the absorptive capacity of soil and the flow capacity of rivers, streams, and coastal areas. This causes a watercourse to overflow its banks onto adjacent lands. Floodplains are, in general, those lands most subject to recurring floods, situated adjacent to streams and rivers. These are therefore "flood-prone" and are hazardous to development activities if the vulnerability of those activities exceeds an acceptable level; therefore affecting livelihood of the region. Eastern Gangetic Flood Plain particularly Bihar has been found to be most prone to frequent flood severely affecting agro-ecosystem and livelihood of the region. The use of remotely sensed data facilitates the synoptic analyses of flood at different spatio-temporal scale depending upon the spatial and temporal resolution of the sensor in use. In this study, an attempt has been made to make an use of coarse spatial (1 km) combined with high temporal (10 days) resolution component of SPOT VEGETATION data to monitor the inundation and recession pattern of flood (i.e. flood dynamics) during the major flood event year 2003 in Eastern Gangetic Flood plain covering Bihar state only. Ten days composite vegetation products taken for the period May 2003 to April 2004 were preprocessed and analyzed. It is very well known that NDVI data from a satellite sensor is primarily related to vegetation changes and follows annual cycle of growth and decline. But clouds and poor atmospheric conditions usually depress NDVI values causing sudden drops in NDVI which are not compatible with the gradual process of vegetation growth and is considered as noise and removed using FASIR (Fourier Adjusted Sun Zenith Angle Corrected Interpolated and Reconstructed) Technique.
Extent of flooded area was delineated at every 10 days interval resulting in inundation pattern till it attains the peak followed by the recession pattern of the flood. The processed VEGETATION data products were also analyzed for mapping cropping pattern of the year. Crop damage due to flood was assessed and spatio-temporal distribution of crops of the area was linked to flood dynamics for understanding its impact on agro-ecosystem of the region. It was revealed that multitemporal data though having coarse spatial resolution was especially advantageous to study the dynamic feature like flood and crop at regional scale. Information on flood dynamics led to know its impact on the flood plain in terms of damage to agricultural crops and adoptive strategies for agricultural practices to live with flood.
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