Abstract:We report the successful case of a rapid response to a flash flood in I-Lan County of Taiwan with a map of inundated areas derived from COSMO-SkyMed 1 radar satellite imagery within 24 hours. The flood was caused by the intensive precipitation brought by Typhoon Soulik in July 2013. Based on the ensemble forecasts of trajectory, an urgent request of spaceborne SAR imagery was made 24 hours before Typhoon Soulik made landfall. Two COSMO-SkyMed images were successfully acquired when the center of Typhoon Soulik had just crossed the northern part of Taiwan. The standard level-1b product (radiometric-corrected, geometric-calibrated and orthorectified image) was generated by using the off-the-shelf SARscape software. Following the same approach used with the Expert Landslide and Shadow Area Delineating System, the regional threshold of each tile image was determined to delineate still water surface and quasi-inundated areas in a fully-automatic manner. The results were overlaid on a digital elevation model, and the same tile was visually compared to an optical image taken by Formosat-2 before this event. With this ancillary information, the inundated areas were accurately and quickly identified. The SAR-derived map of inundated areas was OPEN ACCESSRemote Sens. 2015, 7 11955 published on a web-based platform powered by Google Earth within 24 hours, with the aim of supporting the decision-making process of disaster prevention and mitigation. A detailed validation was made afterwards by comparing the map with in situ data of the water levels at 17 stations. The results demonstrate the feasibility of rapidly responding to a typhoon-induced flood with a spaceborne SAR-derived map of inundated areas. A standard operating procedure was derived from this work and followed by the Water Hazard Mitigation Center of the Water Resources Agency, Taiwan, in subsequent typhoon seasons, such as Typhoon Trami (August, 2013) and Typhoon Soudelor (August, 2015).
Water reservoirs are the primary source of freshwater for most cities around the world. To monitor the dynamic changes in reservoir water quality, however, we need an innovative platform that is able to observe the entire reservoir with both high-spatial- and high-temporal-resolution. Formosat-2 is the first commercial satellite dedicated to site surveillance with a high-spatial-resolution sensor placed in a daily revisit orbit (2 m in panchromatic and 8 m in multispectral). In this research, we developed two empirical algorithms to map the water contents of Chlorophyll-a (Chl-a) and suspended solids (SS) from Formosat-2 multispectral imagery. These algorithms are derived from a total of 53 pairs of water-quality and surface-reflectance data collected during 14 field campaigns at Tsengwen Reservoir from 2005 to 2006. A total of 15 Formosat-2 images were selected from all available images of Tsengwen Reservoir taken in 2006 to generate water quality maps of Chl-a and SS using our new algorithms. Results from this study indicate that the Chl-a and SS concentrations can be retrieved from Formosat-2 imagery with deviations of 56% and 43%, respectively. This is the first time that the reservoir water quality can be mapped from a high-spatial-resolution satellite image at such a high-temporal-resolution. To facilitate the administration of water resources, this research encourages the application of Formosat-2 high spatiotemporal imagery in identifying areas of poor water quality and monitoring the dispersal pattern of pollutant plumes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.