# Potential and Limitations of Open Satellite Data for Flood Mapping  
[PERSON]  
1 National Research Council of Italy, Research Institute for Geo-Hydrological Protection (CNR-IRPI), Strada delle Cacce 73, 10135 Torino, Italy; [EMAIL_ADDRESS]  
[PERSON]  
1 National Research Council of Italy, Research Institute for Geo-Hydrological Protection (CNR-IRPI), Strada delle Cacce 73, 10135 Torino, Italy; [EMAIL_ADDRESS]  
[PERSON]  
2 National Research Council (CNR) of Italy, Institute for the Electromagnetic Sensing of the Environment (IREA), via Diocleziano 328, 80124 Napoli, Italy; calo.firea.cnr.it (F.C. ); [EMAIL_ADDRESS] (A.P.) [PERSON]  
2 Department of Earth and Environmental Science, University of Pavia, Via Ferrata 1, 27100 Pavia, Italy; [EMAIL_ADDRESS]  
[PERSON]  
3 Department of Earth and Environmental Science, University of Pavia, Via Ferrata 1, 27100 Pavia, Italy; [EMAIL_ADDRESS]  
Footnote  
provides synthetic aperture radar (SAR) and multispectral data with global coverage, high-frequency pass, and high spatial resolution. Other examples of free remote sensing programs are Landsat, which has provided data since 1972 [6], and the MODIS daily satellites giving multispectral images [7]. These data are often available with the first level of atmospheric or radiometric calibration, allowing their use by different types of users and not only experts in remote sensing processing. An example of a user-friendly data portal is the Worldview [8] service for the visualization of MODIS products or the G-Pod service of European Space Agency (ESA), which allows the on-line processing of ENVISAT and Sentinel-1 SAR data [9; 10]. In addition, free GIS plugins allow the downloading and processing of free multispectral satellite images [11]. The availability of these resources is useful for the management of natural hazard effects. Every year, flood events cause great economic losses and victims [12]. For this reason, precise flood mapping and modelling are essential for flood hazard assessment [13], damage estimation [14] and sustainable urban planning to properly manage flood risk [15]. In such a context, satellite remote sensing is currently a low-cost tool that can be profitably exploited for flood mapping [16; 17; 18]. Extraction of flooded areas can be performed by using multispectral satellite data and their derived indexes [19; 20; 21; 22; 23; 24], SAR images [25; 26; 27; 28; 29; 30; 31], or a combination of these data [32]. Other types of satellite data can be useful to improve flood mapping. For instance, the digital elevation models (DEMs) derived from satellite data, e.g., Shuttle Radar Topography Mission (SRTM) and ASTER, were also used to estimate flood-prone areas or to improve a SAR/multispectral data-based map [33; 34; 35; 36]. In addition, water storage data from the GRACE satellite [37] or soil moisture data from ASCAT [38] were used to derive flood indicators. Each remote sensing technique for flood mapping presents advantages and drawbacks [39] that must be evaluated on a case-by-case basis. The frequent passes of satellites and the availability of rapid processing chains allowed the development of services providing automatic and quasi-real time flood mapping such as, for example, the Copernicus Emergency Management Service (EMS) performed by the European Union [40; 41], the Global Flood Detection System [42; 43] and the NASA Global Flood Mapping System [44]. However, these services provide rapid mapping products that can be affected by uncertainty and are not always validated [45]. Maps of flooded areas produced by official authorities and based on bespoke aerial photos and field surveys are more accurate, although they are time-consuming and require higher costs to be generated. Consider also that flood mapping can be affected by uncertainty related, for instance, to hydraulic models or the resolution of DEMs [46]. In this work, we present a multi-sensor, low-cost and user-friendly approach for flood inundation mapping.