Flume experiments on the geomorphic effects of large wood in gravel-bed rivers

2020 ◽  
pp. 1609-1615
Author(s):  
D. Ravazzolo ◽  
G. Spreitzer ◽  
H. Friedrich ◽  
J. Tunnicliffe
Keyword(s):  
Large Wood ◽  
Flume Experiments ◽  
Gravel Bed ◽  
Gravel Bed Rivers

scholarly journals Effect of stress history on sediment transport and channel adjustment in graded gravel-bed rivers

2021 ◽  
Author(s):  
Chenge An ◽  
Marwan A. Hassan ◽  
Carles Ferrer-Boix ◽  
Xudong Fu
Keyword(s):  
Sediment Transport ◽  
Critical Shear Stress ◽  
Transport Rate ◽  
Low Flow ◽  
Flood Event ◽  
Flume Experiments ◽  
Stress History ◽  
Gravel Bed ◽  
Sediment Transport Rate ◽  
Gravel Bed Rivers

<p>Recently, there has been an increasing attention on the environmental flow management for the maintenance of habitat diversity and ecosystem health of mountain gravel-bed rivers. More specifically, much interest has been paid to how inter-flood low flow can affect gravel-bed river morphodynamics during subsequent flood events. Such an effect is often termed as “stress history” effect. Previous research has found that antecedent conditioning flow can lead to an increase in the critical shear stress and a reduction in sediment transport rate during a subsequent flood. But how long this effect can last during the flood event has not been fully discussed. In this study, a series of flume experiments with various durations of conditioning flow are presented to study this problem. Results show that channel morphology adjusts significantly within the first 15 minutes of the conditioning flow, but becomes rather stable during the remainder of the conditioning flow. The implementation of conditioning flow can indeed lead to a reduction of sediment transport rate during the subsequent hydrograph, but such effect is limited only within a relatively short time at the beginning of the hydrograph. This indicates that bed reorganization during the conditioning phase, which induce the stress history effect, is likely to be erased with increasing intensity of flow and sediment transport during the subsequent flood event.</p>

scholarly journals Effect of stress history on sediment transport and channel adjustment in graded gravel-bed rivers

2020 ◽  
Author(s):  
Chenge An ◽  
Marwan A. Hassan ◽  
Carles Ferrer-Boix ◽  
Xudong Fu
Keyword(s):  
Sediment Transport ◽  
Critical Shear Stress ◽  
Transport Rate ◽  
Low Flow ◽  
Flood Event ◽  
Flume Experiments ◽  
Stress History ◽  
Gravel Bed ◽  
Sediment Transport Rate ◽  
Gravel Bed Rivers

Abstract. With the increasing attention on environmental flow management for the maintenance of habitat diversity and ecosystem health of mountain gravel-bed rivers, much interest has been paid to how inter-flood low flow can affect gravel-bed river morphodynamics during subsequent flood events. Previous research has found that antecedent conditioning flow can lead to an increase in the critical shear stress and a reduction in sediment transport rate during a subsequent flood. But how long this effect can last during the flood event has not been fully discussed. In this paper, a series of flume experiments with various durations of conditioning flow are presented to study this problem. Results show that channel morphology adjusts significantly within the first 15 minutes of the conditioning flow, but becomes rather stable during the remainder of the conditioning flow. The implementation of conditioning flow can indeed lead to a reduction of sediment transport rate during the subsequent hydrograph, but such effect is limited only within a relatively short time at the beginning of the hydrograph. This indicates that bed reorganization during the conditioning phase, which induce the stress history effect, is likely to be erased with increasing intensity of flow and sediment transport during the subsequent flood event.

scholarly journals Effect of stress history on sediment transport and channel adjustment in graded gravel-bed rivers

2021 ◽  
Vol 9 (2) ◽  
pp. 333-350
Author(s):  
Chenge An ◽  
Marwan A. Hassan ◽  
Carles Ferrer-Boix ◽  
Xudong Fu
Keyword(s):  
Sediment Transport ◽  
Critical Shear Stress ◽  
Transport Rate ◽  
Low Flow ◽  
Flood Event ◽  
Flume Experiments ◽  
Stress History ◽  
Gravel Bed ◽  
Sediment Transport Rate ◽  
Gravel Bed Rivers

Abstract. With the increasing attention on environmental flow management for the maintenance of habitat diversity and ecosystem health of mountain gravel-bed rivers, much interest has been paid to how inter-flood low flow can affect gravel-bed river morphodynamics during subsequent flood events. Previous research has found that antecedent conditioning flow can lead to an increase in critical shear stress and a reduction in sediment transport rate during a subsequent flood. However, how long this effect can last during the flood event has not been fully discussed. In this paper, a series of flume experiments with various durations of conditioning flow are presented to study this problem. Results show that channel morphology adjusts significantly within the first 15 min of the conditioning flow but becomes rather stable during the remainder of the conditioning flow. The implementation of conditioning flow can indeed lead to a reduction of sediment transport rate during the subsequent hydrograph, but such an effect is limited to within a relatively short time at the beginning of the hydrograph. This indicates that bed reorganization during the conditioning phase, which induces the stress history effect, is likely to be erased with increasing intensity of flow and sediment transport during the subsequent flood event.

scholarly journals Displacement length and velocity of tagged logs in the tagliamento river

2013 ◽  
Vol 44 (2s) ◽  
Author(s):  
Diego Ravazzolo ◽  
L. Mao ◽  
B. Garniga ◽  
L. Picco ◽  
M.A. Lenzi
Keyword(s):  
Cross Sections ◽  
Positive Relationship ◽  
Transport Processes ◽  
Large Wood ◽  
Flood Events ◽  
Gravel Bed ◽  
North East ◽  
High Magnitude ◽  
Tagliamento River ◽  
Gravel Bed Rivers

Large wood enhance the dynamics of geomorphic processes in river systems, increases the morphological complexity of the channel bed, and provides habitats for fish and invertebrates. On the other side, if transported during high-magnitude events, large wood pieces can increase flood risks in sensitive places such as bridges and narrow cross sections prone to outbank flows. However, the dynamics and mobility of logs in rivers is poorly understood, especially in wide gravel-bed rivers. Recent studies have employed fixed video cameras to assess logs velocity, but little evidence is still available about travel length during flood events of different magnitude. This study was conducted in a valley reach of the Tagliamento river, located in the North East of Italy. The Tagliamento river is approximately 800 m wide in the study area, and is characterized by relatively high natural conditions and complex fluvial dynamics. Log mobility have been studied from June 2010 to October 2011, a period characterized by a relatively high magnitude flood in November 2010. Log mobility and displacement during floods have been measured by implanting active radio transmitters (RFID) in 113 logs and GPS track devices in 42 logs. The first devices allow to recover the log after flood events by using a portable antenna, and to derive the displacement length over the monitoring period, whereas the second devices allows to calculate instantaneous (1 sec) and average log velocity of moving logs. Recovery rate of logs equipped with RFID and GPS was about 50% and 60%, respectively. A preliminary analysis of the data collected indicates that there is a positive relationship between displacement length and the peak of flood events, as well as a positive relationship between log velocity and the flood magnitude. Also, a critical flow rate over which logs stranded on active bars can be transported has been identified. The ability to predict wood mobility in gravel-bed rivers could allow to define better strategies of river management and restoration, by improving the ability to understand wood transport processes and calibrate budgets of wood in rivers.

Comparing gravel-bed rivers in paired urban and rural catchments of southeastern Pennsylvania

Geology ◽  
2000 ◽  
Vol 28 (1) ◽  
pp. 79-82 ◽  
Author(s):  
J. E. Pizzuto ◽  
W. C. Hession ◽  
M. McBride
Keyword(s):  
Gravel Bed ◽  
Gravel Bed Rivers

UNRAVELLING THE ROLE OF VEGETATION IN THE AVULSION HISTORY OF GRAVEL-BED RIVERS

2018 ◽  
Author(s):  
Daniel Donahue ◽  
◽  
José Antonio Constantine ◽  
Gregory B. Pasternack
Keyword(s):  
Gravel Bed ◽  
History Of ◽  
Gravel Bed Rivers

scholarly journals Flume Experiments Evaluating the Efficacy of a Large Wood Trap Featuring Horizontal Rods

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1837
Author(s):  
Mayuko Furukawa ◽  
Daizo Tsutsumi ◽  
Hironori Muto ◽  
Taro Uchida ◽  
Takuro Suzuki ◽  
...  
Keyword(s):  
Relative Length ◽  
Large Wood ◽  
Basic Information ◽  
Trapping Rate ◽  
Supply Rate ◽  
Flume Experiments ◽  
Water And Sediment ◽  
Constant Rate

Large wood (LW) disasters, which often accompany sediment-related disasters, occur worldwide. To prevent and mitigate such disasters, we developed a unique LW trap featuring horizontal rods aligned with the flow. When LW enters the trap, it is scooped up by the rods and thus separated from water and sediment. We explored trapping efficacy using a flume of slope 0.087. Water circulated at a constant rate of 1.8 L/s, LW was added to the flow, and the trapping rates were measured. We focused on the relative wood length (Lw) with respect to the horizontal rod spacing (Sr), the number of LW units supplied, and the supply rate. A longer relative length (Lw/Sr) of LW was associated with a higher trapping rate. The trapping rate was also high when the LW number or supply rate was high. The critical Lw/Sr value was 1.5; below this value, LW was not trapped. This study yields the basic information needed to design traps featuring horizontal rods to mitigate LW-related disasters.

Unobstructed and Obstructed Turbulent Flow in Gravel Bed Rivers

2005 ◽  
Vol 131 (8) ◽  
pp. 635-645 ◽  
Author(s):  
Hans M. Tritico ◽  
Rollin H. Hotchkiss
Keyword(s):  
Turbulent Flow ◽  
Gravel Bed ◽  
Gravel Bed Rivers
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