URBAN’S RIVER FLOOD ANALYSING USING SENTINEL-1 DATA CASE STUDY: (GORGANROOD, AQ’QALA)

Abstract. Flood is one of the greatest disasters in the world, and the cause of a lot of damages to buildings and Agricultural products every year. Gorganrood river crossing the city of Aq’qala and it is always under flood risk. In the spring, due to the high intensity rainfall and melting of the snow, upstream areas bring much water into the Gorganrood river. On 23rd March, 2019 occurred a terrible flood in Aq’qala passing discharge 650 (m^3/s), it would occur every 100 years in this river. This river in normal time is passing discharge approximately 120 (m^3/s). A large of an urban and non-urban area was affected by this flood and mapping and analyzing of this flood have a key role for river and disaster management. Remote sensing is one of the best ways to flood mapping, especially in flood time weather is cloudy, Therefore, Synthetic Aperture Radar (SAR) images had high potentiality for flood analysis. In this study the Sentinel-1 data used for flood studying due to free available and shorter revisit time. After the processing has done, by selecting the VV band the flooded areas detected. After that overlapped the images and combination of RGB bands and the change the value of pixels, at last, we will be able to obtain the flood mapping images for Gorganrood river. In the primary days of the flooding, almost all the northern regions of the city were flooded, and during a week about 96.8 (km^2) city flooded.