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Flood Characterisation and Inundation Pattern Mapping using Radarsat Imagery for Rice Vulnerability Assessment

Kundu, Sananda (2010) Flood Characterisation and Inundation Pattern Mapping using Radarsat Imagery for Rice Vulnerability Assessment.

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Abstract:Nuna River basin is situated near the coastal area of Orissa which is frequently affected by disastrous floods and adversely affect the life of people and property. River overflows the banks or enters the region due to the breaching of the embankments and races through the agricultural land and settlements to cause havoc in the region. Flood disaster is difficult to predict but the route which it follows to inundate the region can be assessed to reduce the severity of the loss. The main objective of this research is inundation pattern mapping and rice vulnerability assessment. Radarsat images have been used for extracting flooded areas, depth and duration and also for identifying flooded paddy fields by backscatter values. To assess the pattern of flood inundation of the area and rice fields coming under the influence of flood, the path which flood water is following during its progress through the region and also while it is receding from the study area has been mapped and analysed with respect to the geomorphology, elevation and depth. This pattern of flow is directly related to the paddy vulnerability as it will be possible to understand the agricultural fields which will be directly affected by flood. Flood inundation pattern has been assessed from the temporal RADARSAT images of three years of 2003, 2006 and 2008 by relating it to the grid of 50*50m in order to find out the relation of the flood pattern with geomorphology, DEM and different flood characteristics like flood extent, depth and duration. Flood recession pattern is obtained from the year 2003 and flood progression pattern is obtained from 2006 and 2008. The results clearly show the flood pattern of the area from the analysis of three years inundation and that path can be used to consider the area which will come under the direct effect of flood. The flood pattern is also related to the damage of crops of the region which forms the basis of economy of the study area. The identification of the flooded paddy fields has been done from the backscatter coefficients of the RADARSAT images as paddy fields are difficult to identify during floods. Detecting the flooded paddy fields directly from the images will also help in indicating the vulnerable area as field visit during flood may become dangerous sometimes. The study includes recognition of flooded paddy fields from the Radarsat imagery and distinguishing it from the non flooded paddy, settlements and water bodies by showing variation in the backscatter values. The growth stage of paddy has been given by doing field survey and co-relating it with the daily rainfall data. This has been done to consider the paddy crop which comes under damage. Vulnerability assessment of paddy crops includes vulnerability assessment with respect to the depth and duration of flood. Paddy plants are water intensive plants, so low depth of water of less than 1m is not harmful for paddy and therefore they remain less vulnerable. But long duration of water in the field may affect it. While flood depth with more than 2m makes the plants highly vulnerable even if the duration is less. Vulnerability of paddy has been shown here for 2003, 2006 and 2008 which shows that in all the years’ paddy fields are highly vulnerable to the flood inundation and because of more depth of water farmers face huge loss. Vulnerability assessment has been done on the basis of field observations. 2003 and 2008 have shown maximum loss as the flood was much disastrous during these two years while 2006 loss is little less with respect to the area under damage. A damage calculation is done on the basis of field information. It includes the variation in the damage of paddy when flood occurs at different stages of growth like when flood comes at the initial stage, damage is much less with respect to the monetary term than the flood occurrence at the middle or mature stage. This is again related to the flood depth and duration. This also reflects the damage the region may experience if flood occurs at different times. Key words: Flood Inundation Pattern, Geomorphology, DEM, RADARSAT, Backscatter, Paddy Growth Stage, Vulnerability, Damage.
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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