Morphological Changes of the Lower Tedori River, Japan, over 50 Years

Abstract

Long-term variation in the morphological characteristics of rivers is complicated as a result of temporally and spatially variable natural processes and anthropogenic disturbances. Better understanding of their relationship is therefore important for river basin management. The present study conducted a detailed analysis of a long-term dataset consisting of a 58-year topographic survey and related data on human impact to clarify the long-term variation in the morphological characteristics of the lower Tedori River in Japan. An empirical model was established through the assessment of spatiotemporal variations in nonlinear rates of adjustment. The results indicated that sediment extraction and dam construction profoundly affected the morphological characteristics of the lower Tedori River and that the vertical adjustment of the river channel experienced five phases. Degradation occurred from 7 to 16 km upstream from the river mouth over all phases. Two aggradation phases following two degradation phases were observed from the river mouth to 2 km upstream. Aggradation and degradation phases appeared alternately from 2 to 7 km. The representative nonlinear rates of vertical adjustment in the second phase were the highest compared with those in the other phases in the entire reach. The correlation analysis revealed that the incision phase was mostly coupled with channel narrowing, while widening followed the deposition phase. It was deduced from aerial photo analysis and a comparison between slope and empirical critical slope that the pattern in the lower Tedori River was braided during the period 1950–2000.

Impacts of sediment transported downstream from the 2015 deep‐seated landslide in Mt. Hakusan, Japan

“…Hai et al (2014) investigated the long‐term changes in the Tedori River channel and observed a lowering of the riverbed by 0.5–3.5 m from 1950 to 1991, resulting in a loss of 12.7 × 10 6 m 3 and identified continuous sediment extraction as the main cause of this depletion during that period. Hai et al (2019) stated that sediment extraction and dam construction had a significant impact on the morphological characteristics of the lower Tedori River.…”

“…The phenomenon of riverbed heightening continued until 2021 but at a lower rate Hai et al (2014). investigated the long-term changes in the Tedori River channel and observed a lowering of the riverbed by 0.5-3.5 m from 1950 to 1991, resulting in a loss of 12.7 Â 10 6 m 3 and identified continuous sediment extraction as the main cause of this depletion during that period Hai et al (2019). stated that sediment extraction and dam construction had a significant impact on the morphological characteristics of the lower Tedori River.Similarly, riverbed degradation (Figure6) occurred in all 17 sections before the landslide, whereas deposition was observed after the landslide in 2015 and declined gradually.…”

19th Annual Meeting of the Asia Oceania Geosciences Society

“…Long-term morphological changes in rivers depend not only on the natural processes but also on anthropogenic activities since rivers are very dynamic to changes in river flow and sediment supply (Hai et al, 2019). Recently, global climate change has become a hot topic for the morphological changes of rivers worldwide due to frequent floods and droughts affecting the river flow and sediment supply.…”

Implications of Land Use and Cover Changes on Upper River Rwizi Macro-Watershed Health in South Western Uganda

“…Secondly, it is manifested indirectly in the form of deforestation, social and economic activities in river catchments [5]. Intensive human activities can indirectly impact more dynamic changes of natural processes, which may alter river processes and their subsequent hydroecological services [8].…”