Research Highlight

Sediment Control Function of River Notches

Pubdate:2017-11-28    From: ANDF    Views:

On August 8, 2009, Typhoon Morakot brought a record-high rainfall of nearly 3,000 mm over a period of three days, triggered a great number of landslides and debris flows, and caused the worst sediment disaster in Taiwan (Chen et al. 2011; Kuo et al. 2013; Shieh et al. 2010; Shieh et al. 2009). Surveys after the typhoon found that, some of the sediment produced upstream was deposited right before the constricted sections of the river, and was gradually moved downstream in later years. The authors recognized that the temporary sediment-trapping at river notches after sediment disaster events followed by gradual release of that sediment warranted further investigation because it could significantly minimize catastrophic impacts downstream. This recognition provided the motivation for this study of the river notch buffering effect on sediment.

The sediment control function has a relationship with the occurrence of choking in a river notch, which results in flow regime and sediment transport rate changes upstream of the notch. A choking condition is also applied in the experimental setup in this study. In this study, flume experiments were designed to investigate the influence of river notch width contraction on the sediment control function. The results of these flume tests were compared to numerical simulations. In this paper the major mechanism of sediment control of river notches is concluded to be related to the multiple interactions among flow hydraulic, sediment transport capacity, and riverbed morphology, and the multiple interactions could be explained and modeled reasonably well by the flume experiment and numerical simulation in this study.

The results of research works have been published on the journal of mountain science Lin, C. H., Liu, C. J., Lin, S. H, Shieh, C. L. (2017). Sediment Control Function of River Notches. Journal of Mountain Science (in Press).https://doi.org/10.1007/s11629-017-4546-1.

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Figure 1  Validation of water surface for R4-Lc40-S3

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Figure 2  Validation of sediment deposition under R4-Lc40-S3-A

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Figure 3  (a) to (d) Dynamic response of bottom shear stress, sediment transport rate, and bed elevation