Estimation of water boundaries and evaluation of flood risk for a reservoir using GNSS multipath reflectometry

Using global navigation satellite systems interferometric reflectometry (GNSS-IR) as a technology, a single GNSS receiver can approximate neighboring environmental factors. Signal-to-noise ratio (SNR) measurements from a geodetic GNSS receiver contain interference patterns caused by reflected and direct signals. The frequencies of interference patterns in water applications are generally utilized to retrieve the water level. The cutoff elevation angle can be used to estimate the significant wave height (SWH). This study is the first study to apply GNSS-IR to estimate the water boundary. The water level and SWH were also estimated. Many artificial or natural hydrous slopes are inclined, and the SNR oscillation significantly differs between inclined reflecting surfaces and horizontal water reflecting surfaces. The cutoff elevation angle is used to detect this difference in this work. The relationship between the cutoff elevation angle and water boundary was deduced and implemented to estimate the water boundary. In addition, the reservoir flood risk was evaluated according to SWH retrievals and empirical formulas. The estimated and actual water boundaries were similar, and there was no flood risk for the experimental reservoir. The results highlight the potential of GNSS-IR technology to monitor and water boundaries and be involved in flood risk evaluation. Finally, an example of an integrated application of GNSS to monitor reservoirs is discussed.