Research Topics
Deep learning for multilabel classification of coral reef conditions in the Indo-Pacific using underwater photo transect method
Research Overview Because coral reef ecosystems face human activities and climate change threats, coral reef conservation programs are implemented worldwide. Monitoring coral health provides references for guiding conservation activities. However, current labor-intensive methods result in a backlog of unsorted images, highlighting the need for automated classification. Few studies have simultaneously utilized accurate labels along with updated algorithms and datasets. This study aimed to create a dataset representing common coral reef conditions and associated stressors in the Indo-Pacific. Concurrently, it assessed existing classification algorithms and proposed a new multilabel method for automatically detecting coral reef conditions and extracting ecological information. A dataset containing over 20,000 high-resolution coral images of different health […]
UAV-based seagrass wrack orthophotos classification for estimating blue carbon
Research Overview When seagrass such as eelgrass flows out of seaweed beds, some of it is washed up and deposited on nearby beaches. This is called seagrass wrack. If it is utilized as a resource or managed well, it can be expected to contribute to blue carbon (carbon sequestered and stored by the marine ecosystem). Monitoring the annual occurrence of seagrass rack is the first step toward such management. In this study, we investigated a method to automatically classify seagrass rack from orthorectified images taken by an unmanned aerial vehicle (drone) along the Futtsu Coast of Tokyo Bay. By using a low-pass filter for preprocessing and ISODATA as the classification […]
Mapping of subtidal and intertidal seagrass meadows via application of the Feature Pyramid Network to unmanned aerial vehicle orthophotos
Research Overview Seagrass meadows, including eelgrass beds, are expected to contribute to blue carbon, defined as carbon sequestered and stored by the ocean, and to provide co-benefits with ecosystem services such as fisheries. Although the restoration of seagrass meadows has long been undertaken by local non-profit organizations, it is necessary to annually monitor the distribution of seagrass meadows in an inexpensive, simple, and high-resolution manner for the certified assessment of carbon dioxide sequestration. In this study, we proposed a method for mapping seagrass meadows distributed from subtidal to intertidal zones by employing consumer-grade aerial drone photography and deep learning of Feature Pyramid Network (FPN). Extensive efforts were made to create […]
Comprehensive Probabilistic Tsunami Hazard Assessment in the Makran Subduction Zone
Research Overview Although earthquakes in the Makran subduction zone (MSZ) can cause tsunamis along the southern coast of Iran, little research has been done because of ethnic minority settlements and undeveloped areas. Chabahar is an important port city in this region and some areas are considered to be an important coastal zone in Iran as a free trade zone. In this study, a probabilistic tsunami hazard analysis (PTHA) method is proposed to apply to the source and coastal areas where information is scarce, and the probability of tsunami height exceedance for different recurrence periods (50, 100, 250, 500, and 1000 years) is presented for several areas along the southern coast […]
Knowledge, awareness, and attitudes toward tsunamis: A local survey in the southern coast of Iran
Research Overview The southern coast of Iran (mainly the coastal area facing the Gulf of Oman) is a potential tsunami and storm surge disaster area, but since it is the least developed area in Iran, little work has been done to prevent such disasters. In recent years, the Iranian government has moved to designate this area as a free trade zone, and it is being positioned as an important area. In addition, there are many ethnic minorities living in the area, and religious influences are significant, so it was assumed that ordinary disaster mitigation measures would not work well. In this study, a questionnaire survey, interviews, and focus group discussions […]
Assessing the natural recovery of mangroves after human disturbance using neural network classification and Sentinel-2 imagery
Research Overview llegal cultivation of shrimp ponds and rice paddies was carried out in the Wumbaik Reserved Mangrove Forest in Rakhine State, Myanmar; many of them have been abandoned under administrative guidance. Although mangrove reforestation has often been carried out around the world, it is costly and tends to be biased toward specific tree species, resulting in a state that differs from the natural state. This study focuses on how abandoned sites can be regenerated in a natural state without human intervention. AS abandoned areas are generally small in size and low-cost method is required especially in developing countries, we adopted Senitnel-2 imagery, which has relatively high resolution and can […]
On the status and mechanisms of coastal erosion in Marawila Beach, Sri Lanka
Research overview Coastal erosion has been a serious threat to the properties and livelihoods of coastal communities on the western coast of Sri Lanka. Since the cause of the erosion was not fully investigated, there were arguments over the selection of countermeasures among beach users. This study found that a decrease in sand supply from rivers was a main reason for the initiation of erosion in the 1980s. An increase in wave energy has become a main cause of coastal erosion since the 2010s. This study suggests the significance of integrated coastal erosion management for the sustainability of the coast and its users. Publication Ratnayakage, S. M. S., Sasaki, J., […]
Groundwater salinization and associated co-contamination risk increase severe drinking water vulnerabilities in the southwestern coast of Bangladesh
Bangladesh is one of the most vulnerable deltas to climate change, sea level rise, inundation, and salt water intrusions. Freshwater salinization is becoming a serious threat to household water security among coastal communities. Our study found that groundwater is severely contaminated with salinity intrusions while co-contaminants were found to be in high concentrations compare with different drinking water standard values, which is completely unsuitable for drinking purposes. In Bangladesh, almost all the people used to drink groundwater as a principal source of water as well as household purposes. Now, it is a great concern to the future sustainable drinking water security and public health problems. Publication Rakib, M.A., Sasaki, J., […]
Hybrid methods combining atmospheric reanalysis data and a parametric typhoon model to hindcast storm surges in Tokyo Bay
Reanalysis data and a parametric typhoon model formula are often used to prepare wind and pressure fields for storm surge hindcasting. However, their optimum selection and usage have not been well established. To enhance the accuracy of wind and pressure fields, two hybrid methods were proposed by applying a parametric typhoon model of Mitsuta–Fujii’s formula, which is determined from the typhoon center to a certain radius of Rb, and then switching to the reanalysis data of ERA-Interim in the outer region through the interpolated transition bandwidth of Wb. In hybrid model I, Rb and Wb were fixed because the time-varying radius of the maximum wind speed was determined by the […]
2019.7.8 iSymWater2019 in Beijing, China
Dr. Sasaki delivered a keynote talk in the international symposium, iSymWater2019, held at Xijiao Hotel in Beijing, entitled "Sustainable Marine Environment and Coastal Disaster Mitigation in Tokyo Bay." One of the organizers of this symposium is School of Environment, Beijing Normal University, with which Graduate School of Frontier Sciences, the University of Tokyo has concluded Memorandum of Understanding (MOU) since May, 2019. This symposium was also reported by China Daily.