4:15 PM - 4:30 PM
[HTT14-04] Topographical comparison of mangrove forests in the Ryukyu Islands using LiDAR technology
Keywords:mangrove, LiDAR, ALS, MLS
Mangroves, inhabiting the tropical and subtropical intertidal zones, are recognized for their unique ecosystems. Also, their role as green infrastructure is anticipated due to their location in the buffer zone between land and sea. However, the distribution characteristics of mangroves have not been fully understood, leading to cases of unsuccessful conservation and afforestation efforts, resulting in mangrove mortality (Lewis, 2005). This difficulty arises from the challenging assessment of microtopography and sediment environments that define the habitats of mangroves (Pham et al., 2018). Mangroves, with roots extending above the ground, submerging underwater during high tide, and often existing in dense conditions, make topographic surveys difficult (Ellison, 2022). Consequently, there are few instances globally where extensive and high-precision topographic data have been obtained.
In this study, we aim to quantitatively measure the distributions and topographies of multiple mangrove forests in the Ryukyu Islands in order to elucidate the relationship between distribution of mangrove species and topography. LiDAR technology was used as a method to understand the topography in mangrove forests. LiDAR enables the rapid acquisition of vast and highly accurate point cloud data, facilitating direct topographical measurements. However, examples of LiDAR surveys using multiple LiDAR platforms in mangrove forests are still limited and methodology is still under development. In this study, both Aerial Laser Scanning (ALS) using Unmanned Aerial Vehicle (UAV) and Mobile Laser Scanning (MLS) using backpack and mobile devices are adopted. The latter was used when traversing the forest was possible. Point cloud data obtained from the surveys are used to create high-resolution Digital Elevation Model (DEM), Digital Surface Model (DSM), and Digital Canopy Height Model (DCHM). The quantitative comparison of mangrove distribution and differences in elevation range for habitat, along with topographic analysis, allows for the examination of the effects of elevation-based tidal inundation and tree distribution. Additionally, a comparison between past aerial photographs and orthophotos created using aerial photos captured by UAV is conducted to explore the relationship between changes in mangrove distribution, topography, and sea-level.
The results of comparing mangrove forests on wide area revealed variations in topography and tree height. Also, changes in mangrove distribution during past 50 years are different. These differences are believed to reflect variations in the establishment ages of mangroves and the species inhabiting different regions.
In this study, we aim to quantitatively measure the distributions and topographies of multiple mangrove forests in the Ryukyu Islands in order to elucidate the relationship between distribution of mangrove species and topography. LiDAR technology was used as a method to understand the topography in mangrove forests. LiDAR enables the rapid acquisition of vast and highly accurate point cloud data, facilitating direct topographical measurements. However, examples of LiDAR surveys using multiple LiDAR platforms in mangrove forests are still limited and methodology is still under development. In this study, both Aerial Laser Scanning (ALS) using Unmanned Aerial Vehicle (UAV) and Mobile Laser Scanning (MLS) using backpack and mobile devices are adopted. The latter was used when traversing the forest was possible. Point cloud data obtained from the surveys are used to create high-resolution Digital Elevation Model (DEM), Digital Surface Model (DSM), and Digital Canopy Height Model (DCHM). The quantitative comparison of mangrove distribution and differences in elevation range for habitat, along with topographic analysis, allows for the examination of the effects of elevation-based tidal inundation and tree distribution. Additionally, a comparison between past aerial photographs and orthophotos created using aerial photos captured by UAV is conducted to explore the relationship between changes in mangrove distribution, topography, and sea-level.
The results of comparing mangrove forests on wide area revealed variations in topography and tree height. Also, changes in mangrove distribution during past 50 years are different. These differences are believed to reflect variations in the establishment ages of mangroves and the species inhabiting different regions.