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Interdisciplinary Perspectives on Remote Sensing for Monitoring and Predicting WaterâRelated Hazards
Ke Zhang1, Yang Hong2,3, and Amir AghaKouchak4
1 State Key Laboratory of HydrologyâWater Resources and Hydraulic Engineering, and Yangtze Institute for Conservation and Development, and College of Hydrology and Water Resources, and CMAâHHU Joint Laboratory for HydroMeteorological Studies, Hohai University, Nanjing, China
2 School of Civil Engineering and Environmental Sciences, University of Oklahoma, Norman, Oklahoma, USA
3 Advanced Radar Research Center, and Center for Spatial Analysis, National Weather Center, Norman, Oklahoma, USA
4 Department of Civil and Environmental Engineering, University of California, Irvine, California, USA
1.1. BACKGROUND
Waterârelated hazards broadly include floods, droughts, rainfallâtriggered landslides, waterâscarcityâinduced soil salinization, and many other interconnected hazards related to water. Floods and droughts, as the core types of waterârelated hazards, have caused numerous losses of human lives and properties throughout human history (Du et al., 2018; Paprotny et al., 2018). With rapid socioeconomic development, population and industrial growth, and other anthropogenic activities over recent decades, many new waterârelated challenges have emerged and imposed increasing threats on the built and natural environment (Lehnert et al., 2017; Wear et al., 2021; Zhang et al., 2021). Moreover, climate change and variability have altered regional to global water cycles (Huntington, 2010; Zhang et al., 2018; Y. Q. Zhang et al., 2016), causing an overall increase in the frequency and intensity of drought and floods around the world (AghaKouchak et al., 2015; Gu et al., 2020). Importantly, climate change is projected to increase the frequency and intensity of drought and floods in the midâ to late 21st century (IPCC, 2013; Wu et al., 2020), and to combine with other anthropogenic activities (AghaKouchak et al., 2021; Zhang et al., 2015; Y. Q. Zhang et al., 2016), leading to a rising risk to humans (Kam et al., 2021; Roudier et al., 2016). The growing impacts of water hazards have spurred research into improving monitoring and prediction of water hazards (Khaing et al., 2019; MakinanoâSantillan et al., 2019), understanding the underlying drivers (Gui et al., 2020), implementing various mitigation and adaptation strategies (Xu et al., 2020), and identifying other relevant factors such as climate change, population growth, exposure, and socioeconomic development.
Historically, waterârelated hazards have been monitored and studied using groundâbased point observations or spatially interpolated grids (AghaKouchak et al., 2014; He et al., 2018; Sheffield et al., 2012). Globally, many areas are not well instrumented to provide sufficient groundâbased observations of precipitation, nearâsurface air temperature, relative humidity, soil moisture, and atmospheric water vapor among other hydrometeorological variables that are necessary for monitoring and investigating the waterârelated hazards (AghaKouchak et al., 2015). In addition, groundâbased gauges are often destroyed by waterârelated hazards such as flash floods, hurricanes, and landslides, making realâtime observation and consistent analysis of waterârelated hazards challenging.
Remote sensing refers to the process of detecting and monitoring an object at a distance from sensors, often onboard platforms such as aircrafts, satellites, unmanned aerial vehicles (UAVs), and towers. Satellite remote sensing of the Earthâs weather started in earnest with the Television and Infrared Observation Satellite (TIROSâ1) mission 1960 (NASA, 1987). TIROSâ1 became a very successful mission and led to a series of additional meteorological satellite missions such as the Nimbus series, the Environmental Science Services Administration Satellite Program (ESSA), the NOAA satellites, QuikScat, Landsat, and Tropical Rainfall Measuring Mission (TRMM). NASA launched the Earth Resources Technology Satellite, which was eventually renamed Landsat 1 in 1975, on 23 July 1972. The Landsat program is a joint NASA/USGS program that provides the longest continuous spaceâbased record of Earthâs land in existence. In 1997, NASA launched the Earth Observing System (EOS) program (https://eospso.nasa.gov) that is composed of a series of satellite missions and scientific instruments in Earth orbit, making it possible for longâterm global observations of the land surface, biosphere, atmosphere, and oceans. There are mainly two common types of Earthâobserving satellites, namely, geostationary satellites and sunâsynchronous polarâorbiting satellites (Njoku, 2014). Geostationary satellites, at altitudes of approximately 36,000 kilometers, revolve at speeds that match the rotation of the Earth so they are stationary relative to the Earthâs surface (Njoku, 2014). This allows the satellites to observe and collect information continuously over specific areas, which are particularly valuable for monitoring weather and forecasting waterârelated hazards (Njoku, 2014). In contrast, sunâsynchronous polarâorbiting satellites are designed to follow a northâsouth orbit, allowing them to cover most of the Earthâs surface over a certain period and collect data at the same local solar time, which are extremely valuable to observe the Earthâs surface to a larger extent and monitor changes over a long time period (Njoku, 2014).
The emergence of remote sensing techniques has provided new avenues to study, monitor, and predict waterârelated hazards (AghaKouchak et al., 2015; Andreas et al., 2020; Argaz et al., 2019; Boni et al., 2020;...
