A comparison and coupling of two novel sensors for intertidal bed-level dynamics observation

Previous studies have revealed the importance of short-term bed-level change on the long-term development of intertidal ecosystems. One of the recent advancements in the short-term bed dynamics observation is the developments of laser-based surface elevation dynamics (LSED) and acoustic surface elevation dynamics (ASED) sensors. These two sensors are developed to automatically monitor tidally induced bed-level changes, and their measuring windows are during emergent and submerged periods, respectively. So far, there is no direct comparison or joint application of these two sensors. Therefore, in the current study, we first compare their observation precision in both laboratory and field conditions. Results show that both sensors' measurements are in good agreement with the manual measurements in the flume (R-2 > 0.99) and field (R-2 approximate to 0.70), indicating the applicability of each sensor in natural environment. Finally, a coupled system (i.e., combining LSED and ASED) is established in a mangrove wetland and both sensors show good agreement with each other (R-2 = 0.69). Results also demonstrate that the coupled observation system can well capture the bed-level change during emergent and submerged conditions, which provides detailed continuous data sets to study the bed-level dynamics within a tidal cycle. Furthermore, large-scale monitoring systems can also be established via mobile network module embedded in the sensor, providing real-time monitoring for bed-level changes, which is valuable to coastal morphological research and vital for detecting deterioration of coastal ecosystems and the services they provide to be able to apply adaptive management.