Author(s): Zilong Xia; Cuiping Kuang; Lei Zhu; Yuhua Zheng; Yunlong Wu
Linked Author(s): Cuiping Kuang
Keywords: Rgus monitoring system; Storm surge; Morphological evolution; Short-term change
Abstract: During a storm event, such as tropical cyclone and cold front, sea surface in coastal water will experience a significant increase due to storm surge. The high wind-waves therefore may break on the beach and strongly stir up local sediment, resulting in an erosion. The morphological impact of these extreme events has drawn great interest of coastal community, however, a real-time in-site observation is still hard to be conducted considering the devastating forcings. The Argus monitoring system, a real-time and omnibearing image observation, is able to record the image information during the storm event with high-definition cameras mounted in a high and safe place. In combined with some post-processing tools, the recorded image can be converted and provide the information of shoreline location and the digital elevation model (DEM) for intertidal zone. It is therefore considered to be a robust technique to estimate the coastal morphological evolution in recent years. The Pingshuiqiao beach is located in the west of Beidaihe district, Hebei province, China. To maintain local ecotourism value, the Argus monitoring system is applied to the beach to monitor shoreline movement, morphological evolution of intertidal zone and berm profile, with six high-definition cameras. In this study, we firstly extract the location of shoreline by processing time exposure images every 30 minutes based on the improved Canny edge detector, which uses a conventional “derivative of Gaussian” filter to detect step edges, i.e., shoreline. Then, the coordinates of shoreline are derived by establishing coordinate relation based on the control points fixed on the beach. Finally, the multi-temporal shoreline coordinates in one day are inputted into ArcGIS for interpolation to set up a DEM. We adopt the above method to process 11-day Argus monitoring results during a storm event on 15-25, July, 2016. The results indicate that the most severe erosion appeared in the western beach with the loss of beach volume per unit width of 132.50m3/m by the storm. After the storm surge, sediment gradually comes back to the beach and deposits there due to the restorative effect of wave in normal weather conditions. Generally, the strong erosion occurs in the supratidal zone and the upper part of intertidal zone, while the deposition in the lower part of intertidal zone during the storm surge in such a wavedominated low tidal range sandy coast. This study clearly presents the morphological change processes at Pingshuiqiao beach based on the Argus monitoring system that can be taken as a practical technique to study on coastal morphology.
Year: 2020