Hydraulics and sediment transport dynamics controlling step-pool formation in high gradient streams: A flume experiment

2008 ◽  
pp. 241-250 ◽  
Author(s):  
Gordon E. Grant
Keyword(s):  
Sediment Transport ◽  
Flume Experiment ◽  
High Gradient ◽  
Transport Dynamics ◽  
Pool Formation

Insight into the sediment dynamics of a high-impact low-frequency mass movement event using single-grain feldspar luminescence in the Pokhara valley, Nepal

2021 ◽  
Author(s):  
Anna-Maartje de Boer ◽  
Wolfgang Schwanghart ◽  
Jürgen Mey ◽  
Jakob Wallinga ◽  
Basanta Raj Adhikari ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Mass Movement ◽  
Low Frequency ◽  
High Impact ◽  
Osl Dating ◽  
Transport Dynamics ◽  
Infrared Stimulated Luminescence ◽  
Single Grain ◽  
Pokhara Valley ◽  
Insight Into

<p>Mass movements play an important role in landscape evolution of high mountain areas such as the Himalayas. Yet, establishing numerical age control and reconstructing transport dynamics of past events is challenging. To fill this research gap, we investigated the potential of Optically Stimulated Luminescence (OSL) dating and tracing methods. OSL dating analyses of Himalayan sediments is extremely challenging due to two main reasons: i) the OSL sensitivity of quartz, typically the mineral of choice for dating sediments younger than 100 ka, is poor, and ii) highly turbid conditions during mass movement transport hamper sufficient OSL signal resetting prior to deposition which eventually results in age overestimation. In this study, we aim to bring OSL dating to the test in an extremely challenging environment. First, we assess the applicability of single-grain feldspar dating of mass movement deposits in the Pokhara valley, Nepal. Second, we exploit the poor bleaching mechanisms to get insight into the sediment dynamics of this paleo-mass movement through bleaching proxies. The Pokhara valley is a unique setting for our case-study, considering the availability of an extensive independent radiocarbon dataset (Schwanghart et al., 2016) as a geochronological benchmark.</p><p>Single-grain infrared stimulated luminescence signals were measured at 50°C (IRSL50) and post-infrared infrared stimulated luminescence signals at 150°C (pIRIR-150). As expected, results show that the IRSL50 signal is better bleached than the pIRIR150 signal. A bootstrapped Minimum Age Model (bMAM) is applied to retrieve the youngest subpopulation to estimate the palaeodose. However, burial ages calculated based on this palaeodose overestimate the radiocarbon ages by an average factor of ~8 (IRSL50) and ~35 (pIRIR150). This shows that dating of the Pokhara Formation with our single-grain approach was not successful. Large inheritances in combination with the scatter in the single-grain dose distributions show that the sediments have been transported prior to deposition under extreme limited light exposure which corresponds well with the highly turbid nature of the sediment laden flood and debris flows that emplaced the Pokhara Formation.</p><p>To investigate the sediment transport dynamics in more detail we studied three bleaching proxies: the percentage of grains in saturation (2D0 criteria), percentage of well-bleached grains (2σ range of bMAM-De) and the overdispersion (OD). Neither of the three bleaching proxies indicate a spatial relationship with run-out distances of the mass movement deposits. We interpret this as virtual absence of bleaching during transport, which reflects the catastrophic nature of the event. While single-grain feldspar dating did not provide reliable burial ages of the Pokhara mass movement deposits, our approach has great potential to provide insight in sediment transport dynamics of high-impact low-frequency mass movement events in mountainous region.</p><p><em>References</em></p><p>Schwanghart, W., Bernhardt, A., Stolle, A., Hoelzmann, P., Adhikari, B. R., Andermann, C., ... & Korup, O. (2016). Repeated catastrophic valley infill following medieval earthquakes in the Nepal Himalaya. Science, 351(6269), 147-150.</p>

Introduction to the special issue on sediment transport dynamics

2001 ◽  
Vol 26 (13) ◽  
pp. 1367-1368
Author(s):  
Michael Church ◽  
Marwan A. Hassan
Keyword(s):  
Sediment Transport ◽  
Special Issue ◽  
Transport Dynamics

scholarly journals Seasonal hydrological and suspended sediment transport dynamics in proglacial streams, James Ross Island, Antarctica

2016 ◽  
Vol 99 (1) ◽  
pp. 38-55 ◽  
Author(s):  
Jan Kavan ◽  
Jakub Ondruch ◽  
Daniel Nývlt ◽  
Filip Hrbáček ◽  
Jonathan L. Carrivick ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Suspended Sediment Transport ◽  
Transport Dynamics ◽  
James Ross Island

Application of ADCPs for Long-Term Sediment Transport Monitoring in Arctic Environments: Examples From the Laptev Sea

2006 ◽  
Author(s):  
Carolyn Wegner ◽  
Jens A. Ho¨lemann ◽  
Torben Klagge ◽  
Leonid Timokhov ◽  
Heidemarie Kassens
Keyword(s):  
Sediment Transport ◽  
Water Samples ◽  
Acoustic Doppler Current Profiler ◽  
Laptev Sea ◽  
Transport Dynamics ◽  
Shelf Seas ◽  
Current Profiler ◽  
Spm Concentration ◽  
Optical Turbidity ◽  
The Laptev Sea

For offshore constructions the knowledge on sediment transport dynamics is essential and the quantification of suspended particulate matter (SPM) is of major importance. The Laptev Sea shelf is one of the largest Siberian shelf seas and ice-covered for about nine months a year. In order to use indirect measuring devices for the quantification of SPM concentration on the Laptev Sea shelf, optical (turbidity meter) and acoustic (ADCP; Acoustic Doppler Current Profiler) backscatter sensors were compared to assess their potential for the investigation of SPM dynamics in an arctic environment. To estimate SPM concentrations from optical backscatter signals, these were converted using the linear relation between the backscatter signals and SPM concentrations derived from water samples. Applying the theoretical interaction of sound in the water with SPM the acoustic backscatter signals were transformed adapting a previously established approach. SPM concentrations estimated from the backscattered signals of both sensors showed a close similarity to SPM concentrations obtained from filtered water samples. While the ADCP offers distinct advantages over the turbidity meter in that it allows measurement of the complete concentration profile, bottom location, and currents, co-deployment of both sensors are recommended for improved SPM measurements.

scholarly journals Drought conditions and sediment transport in the Sabie River

Koedoe ◽  
1995 ◽  
Vol 38 (2) ◽  
Author(s):  
G.L. Heritage ◽  
A.W. Van Niekerk
Keyword(s):  
Sediment Transport ◽  
Riparian Vegetation ◽  
River Sediment ◽  
Storm Events ◽  
Rainfall Events ◽  
Transport Dynamics ◽  
Sediment Transport Capacity ◽  
Reduced Frequency ◽  
Drought Conditions ◽  
Alluvial Material

Drought conditions in the Sabie catchment in the eastern Transvaal (now called Mpumalanga), South Africa, has had an observable effect on the sediment dynamics of the river. Sediment production within the catchment is largely unaffected by a reduction in the frequency and magnitude of rainfall events, although the rate of translocation of the weathered material from the catchment into the river channel is noticeably altered. The infrequent storm events during drought conditions generate a greater sed- iment input to the river from the catchment than a similar-magnitude event under average conditions. This sediment is also less likely to be transported through the system due to the reduced frequency of intermediate flows which act to rework in-channel sed- iment accumulations. Thus, significant accumulations of alluvial material are likely to form at specific locations, particularly where the local sediment transport capacity of the channel is low. Studies of the transport dynamics of the Sabie River, under both nor- mal and drought conditions, reveal that there are major depositional zones between Kruger Weir and Skukuza, and in the area around Lower Sabie. The 1992 drought resulted in a significant build-up of sediment in these areas, with a consequent reduc- tion in geomorphic diversity. This sediment is becoming stabilised due to the lower and less variable flows of the recent drought and associated vegetative colonisation. An increase in the magnitude and frequency of high and intermediate flows is needed to mobilise this accumulated sediment and to prevent its stabilisation by riparian vegetation.

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