Spatial relationship between the distribution of benthic macroinvertebrate and tidal flat geomorphology from UAV LiDAR and Photogrammetry: preliminary results

Abstract

This study assessed the relationship between the spatial distribution of benthic macroinvertebrate and topographic characteristics of mudflats. For this aim, our specific objectives were: (1) to acquire the very high-resolution image from Unmanned Aerial Vehicle (UAV) for species identification of macroinvertebrate based on morphology of burrow, (2) to generate the map of characteristic of tidal flat (sediment facies, channels, TOC, slopes, moisture contents etc.) from UAV photogrammetry, and (3) to generate and compare the high-resolution Digital elevation model (DEM) from UAV LiDAR and photogrammetry. The study site is located in the Hwangdo mudflat, central western coast of Korea. In order to identify and distinguish the fine-scaled (~ 2 cm) burrow of benthic macroinvertebrate, UAV photogrammetry data obtained at an altitude of 6 m for an area of about 30 m by 1500 m, and a very high-resolution (GSD 0.07 mm) images were acquired. The LiDAR data set and photogrammetry data sets captured from an UAV at a flight altitude of 100 m for DEM and geomorphology. The area covered is approximately 1.8 km by 4 km. The overall trend shows a high elevation in the center, and whereas there are considerable gradients in the west, the topography has relatively low relief in the east of the study area. In the analysis of the relationship between sediment facies and distribution of macroinvertebrate, Laomedia astacina, Uca arcuata, and Ilyoplax pingi species were distributed in the relative muddy sediment (western part of study area), and Urechis unicinctus species was distributed in the mixed (eastern part of study area) sediment. It was found that the tidal flat environment and the distribution of macroinvertebrates were very closely related. We demonstrated that with ground resolution of ~0.05 cm it is possible to visibly distinguish macroinvertebrate species based on the burrow morphology and generate the accurate spatial distribution map. Our preliminary results indicated that high-resolution imagery from UAVs are a promising method for construction spatial information of tidal flat.