LONG-TERM (1953-2020) MORPHOLOGICAL CHANGES OF CHIKUGO RIVER, JAPAN
LONG-TERM (1953-2020) MORPHOLOGICAL CHANGES OF CHIKUGO RIVER, JAPAN
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日本筑后河的长期（1953-2020）形态变化
DOI：
10.1142/9789811275449_0043
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发表时间：
2023
期刊：
影响因子：
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通讯作者：
Azhikodan G.
中科院分区：
文献类型：
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作者：
Phyu P.E.;Yokoyama K.;Azhikodan G.
本研究利用1953-2020年的河流断面调查数据，预测筑后河的长期形态变化。研究区域分为河口（0-23 km）、中游（23-50 km）和上游（50-64 km）。计算了各调查年各断面的平均河床高程，分析了纵向高程的长期变化。研究发现，在67年的研究期间，河道形态在空间（0- 64 km）和时间（1953-2020）上都发生了变化，并出现了三种不同的形态变化趋势。从1953年到1993年，疏浚、砂石开采和大坝建设使筑后河的河床高程下降，河口1-4 m，中游2-4 m，上游1-3 m。从1993年到2009年，与第一阶段相比，海拔变化变小，海拔均匀增加（约0.5米）。2009-2020年，由于气候变化灾害导致河流流量和泥沙供应发生变化，观察到不均匀的形态变化。灾害事件不仅增加了河流的流量，而且还从流域带走了更多的泥沙。这些沉积物大部分沉积在中游（50-64 km），使河床高程增加约1-1.5 m。上游（50-64公里）表现出快速和显着的响应类型的灾害，虽然海拔变化几乎是稳定的，由于沉积的滑坡灾害和洪水侵蚀的净结果。河口高程（8-23 km）由于上游泥沙供应不足和高流量的净侵蚀而降低，而0-8 km高程由于8-23 km侵蚀泥沙的沉积而略有升高。因此，气候变化灾害对筑后川地貌动态平衡的影响是不均匀的，尽管与人类活动相比，筑后川的高程变化较小。
This study aims to predict the long-term morphological changes of the Chikugo River using river cross-sectional surveyed data from 1953-2020. The study area was divided into the estuary (0-23 km), middle stream (23-50 km) and upstream (50-64 km). The mean bed elevation of every cross-section in each surveyed year was calculated to analyze the long-term longitudinal elevation changes. Spatial (0-64km) and temporal (1953-2020) changes in channel shapes were found. In addition, three different morphological trends were found during the study period of 67 years. From 1953 to 1993, dredging, sand & gravel mining, and dam construction decreased the bed elevation of Chikugo River; 1-4 m for estuary, 2-4 m for middle stream and 1-3 m for upstream. From 1993-2009, elevation changes became less compared to the first period and elevation increased uniformly (about 0.5 m). From 2009-2020, non-uniform morphological changes were observed due to changes in river flow and sediment supply by climate change disasters. The disaster events not only increase the river flow but also carries more sediments from the watershed. Most of these sediments were deposited in the middle stream (50-64 km) increasing the bed elevation by about 1-1.5 m. The upstream (50-64 km) showed a quick and significant response to the type of disasters although elevation change was almost stable due to the net result of deposition by landslide disaster and erosion by the flood. However, the elevation of the estuary (8-23 km) decreased due to net erosion by high river flow and insufficient sediment supply from upstream while the elevation of 0-8 km increased slightly due to the deposition of eroded sediments from 8-23 km. Therefore, climate change disasters affect the morpho dynamic equilibrium of Chikugo River non-uniformly although elevation changes were less compared to that of human activities.