Evaluation of CYGNSS Observations for Flood Detection and Mapping during Sistan and Baluchestan Torrential Rain in 2020  
[PERSON]  
1 Department of Civil and Environmental Engineering, Norwegian University of Science and Technology NTNU, 7491 Trondheim, Norway; [EMAIL_ADDRESS] (H.N. ); [EMAIL_ADDRESS] (M.H. )1 Department of Civil and Environmental Engineering, Norwegian University of Science and Technology NTNU, 7491 Trondheim, Norway; [EMAIL_ADDRESS] (H.N. ); [EMAIL_ADDRESS] (M.H. )1 Department of Civil and Environmental Engineering, Norwegian University of Science and Technology NTNU, 7491 Trondheim, Norway; [EMAIL_ADDRESS] (H.N. ); [EMAIL_ADDRESS] (M.H. )1 Department of Civil and Environmental Engineering, Norwegian University of Science and Technology NTNU, 7491 Trondheim, Norway; [EMAIL_ADDRESS] (H.N. ); [EMAIL_ADDRESS] (M.H. )1 Department of Civil and Environmental Engineering, Norwegian University of Science and Technology NTNU, 7491 Trondheim, Norway; [EMAIL_ADDRESS] (H.N. ); [EMAIL_ADDRESS] (M.H. )1 Department of Civil and Environmental Engineering, Norwegian University of Science and Technology NTNU, 7491 Trondheim, Norway; [EMAIL_ADDRESS] (H.N. )1 Department of Civil and Environmental Engineering, Norwegian University of Science and Technology NTNU, 7491 Trondheim, Norway; [EMAIL_ADDRESS] (H.N. )1 Department of Civil and Environmental Engineering, Norwegian University of Science and Technology NTNU, 7491 Trondheim, Norway; [EMAIL_ADDRESS] (M.H. )1 Department of Civil and Environmental Engineering, Norwegian University of Science and Technology NTNU, 7491 Trondheim, Norway; [EMAIL_ADDRESS] (H.N. increased evaporation and greater overall precipitation [5]. Increased precipitation, although associated with inland flooding, can also increase the risk of coastal flooding [6]. Flood detection, and subsequently, produced maps, are beneficial in two important phases: During the flood, when we need emergency management planning, and after the flood, for land use planning, defining construction standards, and damage assessment [7]. Heavy precipitation has led floods to occur more frequently in different countries, which have drawn considerable attention over the past years. There are many regions of Iran affected by floods, for instance, heavy rainfall from mid-March to April 2019 led to flooding in 28 of 31 provinces, with the most severe flooding occurring in Golestan, Fars, Kluzestan, and Lorestan [8]. The recent torrential rain in mid-January 2020 in the southeastern region of Iran caused a devastating flood in the Sistan and Baluchestan province. We investigated the latter case in this study. Land surveying and airborne observations are the traditional methods for flood detection, but when when flood detection is conducted on a large scale, these methods are costly and slow. Space-based Remote Sensing (RS) can be considered as a practical alternative that provides up-to-date information from various sensors that have been onboard different satellites. However, there are some limitations in using RS data products for the study of flooding. For instance, optical RS can have its limitations during severe weather conditions and during night. Therefore, in some cases before and after a flood event, the optical RS imagery does not provide the required information [7]. Radar RS in the microwave spectrum can surpass these restrictions because the wave can penetrate clouds and vegetation and can effectively work at night. Among the several radars RS sensors currently in operation, Synthetic Aperture Radar (SAR) imagery provides high spatial resolution data which is typically based on a monostatic configuration. However, the revisit time of satellites with the configuration of the monostatic radar (single satellites), like SAR, is long (more than one week) and cannot offer the desirable continuous high temporal resolution for flood detection purposes. Accordingly, owing to the highly dynamic nature of the flood, SAR images are not used operationally during floods [9; 10; 11].