17:15 〜 18:45
[AHW18-P08] An attempt to understand the water cycle in the western Mekong Delta: comparison of digital elevation models
キーワード：メコンデルタ、地形、土地利用、水循環、デジタルデータセット
Asia’s mega-deltas such as the Ganges-Brahmaputra Delta, Eirrawaddy Delta, and Mekong Delta are home to over 400 million people and more than 10 mega-cities. These mega-deltas support the world’s most productive ecosystems and are critical to the economies, food security, and sustainable development of the entire continent (World Bank, 2021). For instance, the Mekong Delta accounts for about half of Vietnam’s rice production and about sixty percent of freshwater fisheries. However, these mega-deltas are facing various environmental issues such as land subsidence, coastal erosion, and saltwater intrusion due to human activities.
In the region on the left bank side of the Cai Lon River mouth which is located in Kien Giang province, western part of the Mekong Delta, rice cultivation had been widely practiced before the 1990s. However, since the 2000s, the land use has been shifted to a rotation system of rice cultivation and shrimp/crab aquaculture. On the other hand, this region is located far from the Mekong River and has an especially low elevation in the whole delta. Therefore, this region is considered to be vulnerable to the environmental issues mentioned above. This study attempts to understand the current situation of the correlation between the microtopography, land use, and water cycle in this region by integrating actual field observations and the digital datasets of topography, land use, and satellite images. In this presentation, we report on the topographical characteristics found in the ground elevation models.
We obtained the datasets of AW3D30, NASADEM, MERIT DEM, TOPO DEM (Digital elevation model of the Vietnamese Mekong delta based on elevation points from a national topographical map), and AW3D Standard (NTT DATA CORPORATION and RESTEC).
In the topographical maps of the AW3D30, NASADEM, and MERIT DEM, high elevation points are linearly distributed in common. Even considering the effects of the stripe noise and speckle noise, these distributions are obvious. From the comparison with the satellite photos, Google Street View, and field observation, these linear high-elevation points in the topographic maps were considered to be affected by features such as houses and trees. This means that the effect of land use remains in the DEM datasets of not only NASADEM but also MERIT DEM.
As for the AW3D standard (mesh size: 2.5m), the linear distributions of high-elevation points were not found. The topographical map based on this dataset showed a certain correlation between microtopography and land use. This tendency suggests that the microtopography and land use affect interactively. That is, the microtopography regulates land use and the land use deforms the microtopography. On the other hand, from the comparison between the AW3D standard and TOPO DEM, the elevations in the AW3D standard tend to be higher than that in TOPO DEM. This difference may be based on the difference in the geodetic systems between these two datasets.
This study is supported by Global Collaborative Research, Center for Southeast Asian Studies, Kyoto University.
In the region on the left bank side of the Cai Lon River mouth which is located in Kien Giang province, western part of the Mekong Delta, rice cultivation had been widely practiced before the 1990s. However, since the 2000s, the land use has been shifted to a rotation system of rice cultivation and shrimp/crab aquaculture. On the other hand, this region is located far from the Mekong River and has an especially low elevation in the whole delta. Therefore, this region is considered to be vulnerable to the environmental issues mentioned above. This study attempts to understand the current situation of the correlation between the microtopography, land use, and water cycle in this region by integrating actual field observations and the digital datasets of topography, land use, and satellite images. In this presentation, we report on the topographical characteristics found in the ground elevation models.
We obtained the datasets of AW3D30, NASADEM, MERIT DEM, TOPO DEM (Digital elevation model of the Vietnamese Mekong delta based on elevation points from a national topographical map), and AW3D Standard (NTT DATA CORPORATION and RESTEC).
In the topographical maps of the AW3D30, NASADEM, and MERIT DEM, high elevation points are linearly distributed in common. Even considering the effects of the stripe noise and speckle noise, these distributions are obvious. From the comparison with the satellite photos, Google Street View, and field observation, these linear high-elevation points in the topographic maps were considered to be affected by features such as houses and trees. This means that the effect of land use remains in the DEM datasets of not only NASADEM but also MERIT DEM.
As for the AW3D standard (mesh size: 2.5m), the linear distributions of high-elevation points were not found. The topographical map based on this dataset showed a certain correlation between microtopography and land use. This tendency suggests that the microtopography and land use affect interactively. That is, the microtopography regulates land use and the land use deforms the microtopography. On the other hand, from the comparison between the AW3D standard and TOPO DEM, the elevations in the AW3D standard tend to be higher than that in TOPO DEM. This difference may be based on the difference in the geodetic systems between these two datasets.
This study is supported by Global Collaborative Research, Center for Southeast Asian Studies, Kyoto University.