Abstract
Abstract. Flood is a natural hazard influenced by rainfall and dam collapse, which propels release of enormous amount of water. In the last two decades flood is the second largest natural hazards occurred worldwide, which caused serious damage to life properties, settlements and economic activities. Flood mapping is a process that is useful for assessment and reduces the risk factor during the flood. An effective monitoring of flood prone area is necessary to handle GIS techniques and without remote sensing data it is difficult to identify the flooded area in this study Microwave remote sensing plays a lead role in natural hazards, here Synthetic Aperture Radar (SAR) data is the best way for monitoring flood hazards. In this study Southern part of the Kerala is chosen as the study area, In August 2018, during the south west monsoon due to heavy rainfall a severe flood affected the southern part of Kerala which saw a 37% increase in the rate of normal rainfall. The objective of the study is to find the flood zone area using SAR data and estimate the flood occurrence over a period of time. However a satellite imagery of optical data is used to analyse the pre and post event of flood, but during a heavy rainfall, cloud may interrupt the data acquisition. SAR satellite imagery fromSentinel-1A is a cloud penetrating data available in all kind of weather conditions during day and night time, which provides a good source of high resolution data sets. To identify the flood affected area an adapted technology of threshold methodology developed by using SAR data and change detection for the year 2018 and 2019, will illustrate flood extended part in southern part of Kerala. The result shows the estimation of flood extended part of the study area and the damages occurred during a flooded time period of post and pre event, vulnerability assessing of crop and agriculture is to obtain an intensity of the damaged areas which is closely associated with the river channel, the Polarization displays a similar sequence for amount of flooding. The study helps to find the reason of flood extent and to equip with better planning for risk reduction and management during a flooding period.
Highlights
Floods are frequently occurring natural hazards that cause great damage to lives and property (Martinez, & Landuyt, et al, 2019)
In August 2018, during the southwest monsoon due toheavy rainfall a severe flood affected the southern part of Kerala which shows a 37% increase in the rate of normal rainfall as per the report of Central Water Commission (CWC 2018, 2019) in overall comparison between the years of 2019
The flood inundation area were delineated from Sentinel-1A and the permanent water body was delineated by using Sentinel-2 Multi Spectral Image of optical data, the identification of flood area is helps to understand and estimate the vulnerable zone during a disaster
Summary
Floods are frequently occurring natural hazards that cause great damage to lives and property (Martinez, & Landuyt, et al, 2019). Nearly23.34% excess of rainfall august in 2018 and 12.72% in 2019 during the southwest monsoon, this situation resulted the severe cause of flood, out of 14 districts 13 were affected by the flood (CWC 2019; Mishra et al, 2018; sudheer et al, 2019). In this scenario, the present research work have the following objectives to find the flood zone area using SAR data and estimate the flood occurrence over a periodof time, the study adopts a remote sensing data of Sentinel-1A SAR data and Sentinel-2. This research aims to delineate the flooded area using simple techniques that brought out a freely available SAR data
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