5:15 PM - 6:45 PM
[HTT14-P07] Tsunami deposits and Anthropogenic Debris in Coastal Deposits 10 years after the 2011 Tsunami - Combined UAV Photogrammetry, LiDAR and Ground-Penetrating Investigation
Keywords:tsunami, high-resolution topography, Ground Penetrating Radar, coastal environment
The March 11, 2011 tsunami took the lives of an estimated 11,000 with numerous remains still to be returned to their families and a coastal landscape profoundly remodeled both by the tsunami and the post-event anthropogenic structures. Because Japan has densely populated coastal shores (since 70% of the land is covered in mountainous forests), the tsunami was as much the story of a water invasion on land as it was the story of the generation of tons of anthropogenic debris.
Ten years after the event, the coastal environments have been partly restored or reoriented, but how much of the anthropogenic influence is still controlling the coastal sedimentary environment is an essential question to ask both from a purely scientific perspective (question of the Anthropocene) as well as from a practical stance (how much pollution is leaking out of remaining debris, fully or partly buried.
In order to chip at this question, the present contribution has used a combination of drone photogrammetry calibrated against existing post-earthquake LiDAR data (1m tile resolution) and Ground Penetrating Radar, to investigate the subsurface. The collected dataset is centered on a strip of coastal sea-shore located to the South of the renewed Sendai Port. The area is of importance in terms of the presence of debris, because it is a popular spot for surfers and beach-goers.
The drone data is composed of a series of 1500 photographs taken from an altitude < 98 m, which were processed using the now streamlined method of SfM-MVS generated using the Metashape-Pro software. Altitude data and horizontal feature distribution were controlled using the LiDAR data using an iterative process. The Ground Penetrating Radar was acquired using a Mala Pro-Ex and two shielded antennas of 250 MHz and 800 MHz, to capture both the general structure and the presence of punctual objects inferior to a few centimeters.
Both drone data and the Ground Penetrating Radar data have confirmed the presence of metallic buried and semi-buried objects in the coastal sand, and above the shoreface. The visual confirmation of the semi-buried objects did show car parts and structures remaining from the tsunami. Because the elevation at which these are buried is above the present water level the alternation of a dry and wet environment mixed with the coastal saline environment may be lead to local pollution of the surrounding water.
Ten years after the event, the coastal environments have been partly restored or reoriented, but how much of the anthropogenic influence is still controlling the coastal sedimentary environment is an essential question to ask both from a purely scientific perspective (question of the Anthropocene) as well as from a practical stance (how much pollution is leaking out of remaining debris, fully or partly buried.
In order to chip at this question, the present contribution has used a combination of drone photogrammetry calibrated against existing post-earthquake LiDAR data (1m tile resolution) and Ground Penetrating Radar, to investigate the subsurface. The collected dataset is centered on a strip of coastal sea-shore located to the South of the renewed Sendai Port. The area is of importance in terms of the presence of debris, because it is a popular spot for surfers and beach-goers.
The drone data is composed of a series of 1500 photographs taken from an altitude < 98 m, which were processed using the now streamlined method of SfM-MVS generated using the Metashape-Pro software. Altitude data and horizontal feature distribution were controlled using the LiDAR data using an iterative process. The Ground Penetrating Radar was acquired using a Mala Pro-Ex and two shielded antennas of 250 MHz and 800 MHz, to capture both the general structure and the presence of punctual objects inferior to a few centimeters.
Both drone data and the Ground Penetrating Radar data have confirmed the presence of metallic buried and semi-buried objects in the coastal sand, and above the shoreface. The visual confirmation of the semi-buried objects did show car parts and structures remaining from the tsunami. Because the elevation at which these are buried is above the present water level the alternation of a dry and wet environment mixed with the coastal saline environment may be lead to local pollution of the surrounding water.