Flood/Drought Monitoring and Assessment for Food Security

Global warming is intensifying the global water cycle, leading to more frequent and extreme floods and droughts, which have widespread and negative impacts on agriculture. Rapid and effective monitoring of floods and droughts is crucial for addressing the effects of these disasters on agriculture. However, large-scale, high-resolution flood and drought mapping faces significant challenges due to the sparse distribution of hydrological stations and the susceptibility of optical satellites to cloud interference. This thesis proposes leveraging multi-source satellite remote sensing data to overcome the limitations of single-source satellites in terms of temporal, spatial, spectral, and radiometric resolution. Using the GEE platform, rapid flood and drought mapping can be achieved, and by integrating land cover maps and crop maps, the impacts of floods and droughts on agriculture can be assessed. This thesis presents the development of China's first high-resolution flood maps and successfully applies flood monitoring algorithms, initially designed for China, to Greece and Libya. These algorithms have been integrated into Google Earth Engine, making them automatic, rapid, and robust. The high-resolution flood maps are valuable for assessing the impact of floods on agriculture and can support the siting of hydraulic engineering infrastructure. The thesis also introduces a comprehensive drought monitoring system. By utilizing rainfall data, soil moisture data, vegetation indices derived from optical imagery, and terrestrial water storage data from gravity satellites, the thesis successfully monitors meteorological, agricultural, and hydrological droughts through multi-source satellite data. Additionally, the thesis employs Cross Wavelet Transform and Gaussian Copula methods to analyze drought propagation processes and assess the probability of compound droughts. This comprehensive drought monitoring method has been successfully applied in Costa Rica, El Salvador, and Italy. The flood and drought monitoring methods developed in this thesis can be applied globally, offering significant potential for mitigating the negative impacts of droughts and floods.