Monitoring the tidal topography of the north Yellow River Delta with LIDAR data

Tidal flat of the north Yellow River Delta has been strongly influenced by human activities. In this study, the LIDAR (Light Detection and Ranging) data and in-situ topographic data were used to study the characteristics and changes of the tidal flat in this area. The west section of the area is characterized by straight, featureless tidal flat with tidal slope less than 1/1000. The east section is the coast of the abandoned Yellow River section. LIDAR data show the topographic characteristics of the tidal flat. In the northwest of the abandoned Yellow River section, the tidal flat profiles are straight slope with a gradient of about 1/1000. However, a tidal profile in the bay in the east of the abandoned river mouth exhibits upward convex. The profile, along with the plan view of topography and the growing saline seepweed (Suaeda salsa), indicates that the tidal flat is accretional. A strong eroded tidal profile is located in a small bay formed by seawalls. The different patterns of profiles show that the local factors such as local morphology, hydrodynamic conditions, and human activities influence the topography of tidal flats. LIDAR data also show that the bottom of a tidal channel is almost flat. Therefore, through the tidal channels, the sea water rapidly enters the tidal flat when the tide comes in.