###### Abstract  
Remote sensing technologies are extensively applied to prevent, monitor, and forecast hazardous risk conditions in the present-day global climate change era. This paper presents an overview of the current stage of remote sensing approaches employed to study coastal and delta river regions. The advantages and limitations of Earth Observation technology in characterizing the effects of climate variations on coastal environments are also presented. The role of the constellations of satellite sensors for Earth Observation, collecting helpful information on the Earth's system and its temporal changes, is emphasized. For some key technologies, the principal characteristics of the processing chains adopted to obtain from the collected raw data added-value products are summarized. Emphasis is put on studying various disaster risks that affect coastal and megacity areas, where heterogeneous and interlinked hazard conditions can severely affect the population. Earth Observation; remote sensing; coastal regions; river deltas; disaster risk management 2022142884102841  
increases globally, tides have also shown worldwide changes. These risks are accompanied by concerns about the increasing urbanization of coastal regions and related hazards (e.g., tidal-induced nuisance flooding, storm surge). The global sea level has drastically risen during the last century and is expected to increase and possibly accelerate by at least ~60 cm by 2100 because of ocean warming and glacier melt, but these projections are spatially dependent, and some regions may expect larger increases [37; 38]. Projections of future sea-level-rise (SLR) at any coastal location of the world up until the year 2150 under various Shared Socioeconomic Pathway (SSP) scenarios as determined by the IPCC Sixth Assessment Report can be interactively explored using the NASA Sea Level Projection Tool ([[https://sealevel.nasa.gov/ipcc-ar6-sea-level-projection-tool](https://sealevel.nasa.gov/ipcc-ar6-sea-level-projection-tool)]([https://sealevel.nasa.gov/ipcc-ar6-sea-level-projection-tool](https://sealevel.nasa.gov/ipcc-ar6-sea-level-projection-tool))) (accessed on 1 January 2021). SLR results in negative impacts, including coastal erosion [39; 40; 41], flooding [42; 43; 44], freshwater salinization [45; 46; 47], and wetland loss [48]. However, SLR is not uniformly spatially distributed [49; 50] and, consequently, vertical rates of ground subsidence coupled with global SLR pose variable hazards and risks for many coastal population centers. Moreover, anthropogenic processes (e.g., land subsidence connected to groundwater extraction [51], the effects of large land reclamation projects [52], the presence of artificial seawalls) and natural hazards (e.g., storms and storm surge, cyclones and hurricanes, extreme precipitation and flooding) exacerbate the disaster risks in coastal zones and coastal cities, amplifying the vulnerability of the local population. Thus, a detailed understanding of the combined risk of SLR, tidal evolution, storm surge, and ground subsidence in river deltas and coastal regions is of great relevance for reducing disaster risk and fostering resilience. Earth Observation (EO) technologies (e.g., [52; 53; 54; 55; 56; 57; 58; 59; 60; 61; 62; 63; 64; 65; 66]) have been proven to be highly useful for obtaining consistent and frequently updated information on environmental conditions and their temporal variations. Several works have encompassed the study of the atmosphere [67; 68; 69], the ground surface [62; 70; 71; 72; 73; 74; 75; 76], and the sea [77; 78; 79]. The products of these investigations can help monitor the evolution of natural and anthropogenic calamities that affect the population and help local authorities and the national governments design, maintain, and manage effective disaster plans. Disaster management [80; 81; 82; 83; 84; 85] aims to limit the effects of potential losses from hazards, guarantee timely support to victims of disasters, and accomplish a rapid and effective recovery.