| dc.description.abstract | A thorough understanding of surface terrain and the information of inland waterbodies is crucial for flood prevention, irrigation management, and other hydrological applications. Nowadays, multispectral satellite images and LiDAR are widely used to establish underwater model with optical methods. Another possibility is to use single/multi-beam echo sounders to survey in acoustic approaches. However, optical methods are only appropriate for shallow and clean water, while acoustic methods would require considerable cost in dispatching vessels and equipment. The reduced cost of commercial unmanned aerial vehicle (UAV) in recent years has facilitated its wide applications in geoinformatics fields. Owing to its high mobility, UAV provides another kind of mobile platform for the surveying equipment.
In order to update water depth and water volume of 80 ponds in Taoyuan city, this study deploys a mobile bathymetric mapping module for the fieldwork, where each pond requires 3 to 4 operators for 1 to 1.5 hours. An UAV hanging a cellphone and a micro-sonar is designed to measure water depth over water surface. Another UAV is dispatched for aerial photography to build surface terrain around the ponds with a few control points. Finally, the slope and dyke height around the pond are measured for generating the pond DEM. Pond bottom elevation is modeled by the Inverse Distance Weighting of point measurements, and combined with slope and dyke height. The surface model is constructed using the stereo pairs of aerial images and control points. Finally, an integrated model obtained by combining both models is used to derive water storage. The correlation coefficients of water area and storage between our approach and data from the Department of Water Resources, Taoyuan (TYWR) achieve 0.99 and 0.84, respectively. Next, the Simplified Inundation Model (SPM) is used to simulate the flood extent in Bade District, Taoyuan, assuming the ponds are emptied in advance for stormwater detention purposes. Three scenarios were designed to discuss the efficiency of detention rate. Finally, the benefits of pond system and the importance of volume update are described. | en_US |