Performance of alternative methods of bank protection

1992 ◽  
Vol 19 (6) ◽  
pp. 1049-1061 ◽  
Author(s):  
P. F. Doyle
Keyword(s):  
Bank Erosion ◽  
Alternative Methods ◽  
Channel Stability ◽  
Severe Attack ◽  
Gravel Bed ◽  
Training Structures ◽  
Bank Protection ◽  
River Training ◽  
Riprap Protection ◽  
Large Floods

The durability of several common bank protection methods used as less expensive or environmentally acceptable alternatives to toe-trenched angular rock riprap has been documented during the 1980s at seven typical bank erosion sites in British Columbia. Since the sites were uncontrolled examples of actual river training works in operation, natural events hindered a precise comparison of each scheme with toe-trenched angular rock riprap protection. However, of the four alternatives investigated – gravel dykes, tree revetments, riprap with toe apron, and semi-round riprap – all but semi-round riprap performed less than satisfactorily over the years of observation. Documentation of performance is sufficient to conclude that on steep gravel-bed rivers, gravel dykes do not endure; tree revetments require constant maintenance and will not endure large floods, unless extremely well-constructed; toe aprons are not as reliable as toe trenches for the same volume of rock; and well-placed, large semi-round rock performs well under moderately severe attack. Key words: erosion, bank protection, channel stability, river training structures, gravel-bed.

scholarly journals Bank Protection Structures along the Brahmaputra-Jamuna River, a Study of Flow Slides

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2588 ◽  
Author(s):  
Maarten van der Wal
Keyword(s):  
Slope Failure ◽  
Research Question ◽  
Failure Mechanisms ◽  
Flood Plain ◽  
Design Guidelines ◽  
Test Facility ◽  
Training Structures ◽  
Bank Protection ◽  
Flow Slides ◽  
River Training

The planform of the Brahmaputra-Jamuna River followed its natural path in Bangladesh until the construction of bank protection works started to save Sirajganj from bank erosion since the 1930s. Several so-called hardpoints such as groynes and revetments were constructed in the period 1980–2015 and the Jamuna Multipurpose Bridge was opened in 1998. The Brahmaputra Right Embankment and other projects had saved the western flood plain from inundation during monsoon floods. These river training works experienced severe damage by geotechnical failures, mostly flow slides. A flow slide is an underwater slope failure because of liquefaction or a breaching process in the subsoil or a combination of both. The design of most of these training works did not consider the risk of damage by flow slides. All descriptions of the observed damages show that scour phenomena in the channel close to a river training work are a cause of flow slides, besides pore water outflow. The research question was: how can the design of river training works be improved to reduce the risk of damage by flow slides? The main part of the investigation was focussed on reducing local scour holes near river training works. The most promising results are river training works with gentle bank slopes, permeable groynes, bed protections in dredged trenches with gentle side slopes, and methods to increase locally the bearing capacity of the subsoil. It is recommended to increase the knowledge of the failure mechanisms in the Brahmaputra-Jamuna River by improved monitoring in the field, the setup of a database with descriptions of all observed flow slides and the circumstances in which they occur. In addition to these recommendations, a field test facility is proposed to verify the knowledge of the failure mechanisms in that river. These activities will optimise the design of new river training structures with a very low risk of damages by flow slides and geotechnical instabilities and they will contribute to an improvement of the current design guidelines for river training structures.

Identification of channel diversion and bank protection techniques for toorsa river

2020 ◽  
Vol 9 ◽  
Author(s):  
Monika Thapa ◽  
Nimesh Chhetri ◽  
Jigme Yoezer ◽  
Leki Tenzin ◽  
Narendra Chhetri ◽  
...  
Keyword(s):  
Soil Compaction ◽  
Flood Frequency ◽  
Flood Frequency Analysis ◽  
Sieve Analysis ◽  
Sheet Pile ◽  
Bank Protection ◽  
Arc Gis ◽  
River Training ◽  
The Stability

This project aims for desigining of flood embankment structures to accommodate both normal flows as well as the highest designed flood for the return period of 100 years form flood frequency analysis. The new channel dimensions are being determined and embankment protection works for the floods are being designed and recommended. Having found steel sheet pile more advantages and safety, the same is recommended for the river training works. The focus of the project was confined to the channel diversion along with proper embankment works. The methodology included the usage of several approaches such as ARC –GIS to obtain catchment area and cross section of the river,and hydraulics analysis was done using HEC-RAS and the slope/W analysis check was done for the stability of the embankment works. The laboratory test such as sieve analysis, bulk density test, specific gravity test was done to determine the classification of the soil, compaction of the soil, to use different parameter for the desigini g works.

Flow patterns and bed changes due to traditional river training structures “Seigyu”

2020 ◽  
pp. 936-944
Author(s):  
S.A. Kantoush ◽  
M.M. Al Mamari ◽  
Y. Takemon ◽  
M. Saber ◽  
O. Habiba ◽  
...  
Keyword(s):  
Flow Patterns ◽  
Training Structures ◽  
River Training ◽  
Bed Changes

scholarly journals Channel geomorphology differences between stream reaches with grass- or tree-dominated riparian vegetation in southern Manitoba

FACETS ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 336-349
Author(s):  
Sanjayan Satchithanantham ◽  
Henry F. Wilson ◽  
Patsy Michiels ◽  
Melanie Dubois ◽  
Sheng Li ◽  
...  
Keyword(s):  
Riparian Vegetation ◽  
Crop Production ◽  
Forest Cover ◽  
Vegetation Type ◽  
Hazard Index ◽  
Bank Erosion ◽  
Agricultural Watersheds ◽  
Channel Stability ◽  
Cross Sectional ◽  
Canadian Prairies

Removal of trees for pasture or crop production is common along the stream reaches in the Canadian Prairies, resulting in a patchwork of forested and nonforest riparian vegetation along most streams. The effect of vegetation type on channel geomorphology and potential to influence sediment dynamics was studied using eight paired reaches (forested and nonforest) within agricultural watersheds in southern Manitoba, Canada. High potential for bank erosion was observed at all sites (bank erosion hazard index scores), but Pfankuch channel stability scores were significantly higher for forested reaches compared with nonforested reaches. Furthermore, forested reaches had higher width to depth ratios, but flood-prone widths did not differ significantly, resulting in lower entrenchment ratios. Reduced channel width and cross-sectional area in nonforested reaches created an overall reduction of in-stream habitat, increased velocity, and increased potential for exceedance of channel capacity and floodplain access during high-flow events. Channel widening in response to riparian afforestation efforts has been observed in a variety of other locations globally and the results of this study suggest that widening with afforestation can still be anticipated in this region where stream gradients are low, hydrology is dominated by snowmelt, and forest cover is minimal.

Feedbacks between sediment input, bed state and threshold for motion in gravel-bed rivers: an experimental study

2021 ◽  
Author(s):  
Matteo Saletti ◽  
Marwan Hassan
Keyword(s):  
Water Discharge ◽  
State Parameter ◽  
Sediment Supply ◽  
Primary Control ◽  
Channel Stability ◽  
Surface Evolution ◽  
Gravel Bed ◽  
Particle Mobility ◽  
Sediment Input ◽  
Gravel Bed Rivers

<p>In gravel-bed rivers the relation between the magnitude and frequency of sediment input, the threshold for motion and channel stability is still not fully understood.</p><p>Here we present results from a 280-hour long flume experiment, in which poorly sorted sediment was fed episodically in an 18-m long, 2.2%-steep channel. The experiment included 7 consecutive runs lasting 40 hours each characterized by a constant water discharge but different sediment supply regimes (i.e., with no feed, constant feed and sediment pulses). Several measurements of sediment transport, flow depth and bed structures were taken along the flume, to assess how changes in sediment supply influence particle mobility and channel stability.</p><p>Our results show that the surface grain‐size distribution coarsened quickly, developing an armored layer that persisted throughout the entire experiment with only short-lived changes after sediment pulses. Grain clusters and other bed structures developed continuously during the experiments, changing dynamically in response to sediment pulses.</p><p>We estimated the thresholds of motion with three different methods, all of which yielded consistent results. Overall, the threshold for motion increased during the experiment, fluctuating in response to changes in sediment input. Our results provide further evidence to the idea that the threshold for motion in gravel-bed rivers is not a constant, but changes as a state parameter. These changes in our experiments are controlled by (a) the sediment supply regime, (b) the degree of bed structuring, and (c) the history of bed evolution. These outcomes suggest that sediment supply regime is a primary control on bed surface evolution and the channel stabilizing function played by surface structures.</p>

scholarly journals The Evolution of Gravel-Bed Rivers during the Post-Regulation Period in the Polish Carpathians

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 254
Author(s):  
Elżbieta Gorczyca ◽  
Kazimierz Krzemień ◽  
Krzysztof Jarzyna
Keyword(s):  
Conceptual Model ◽  
Economic Activity ◽  
River Regulation ◽  
River Channel ◽  
River Channels ◽  
Subsequent Evolution ◽  
Gravel Bed ◽  
Polish Carpathians ◽  
River Training ◽  
Gravel Bed Rivers

This study provides a conceptual model of the functioning of gravel-bed rivers during the post-regulation period in Poland and forecasts their subsequent evolution. The main difference between fluvial processes during the pre-regulation and post-regulation period is that they are limited to a zone that is currently several times narrower and trapped in a deep-cut channel. During the river post-regulation period, the construction of additional river training works was significantly limited in river channels. Moreover, all forms of economic activity were significantly reduced in the channel free migration zone, particularly bed gravel extraction operations. As a result of these changes, a limited recovery of the functioning and hydromorphology of the river channel occurred via a return to conditions in effect prior to river regulation. In recovering sections of river, the channel gradually broadens, and its sinuosity and number of threads increase. The overall process can be called spontaneous renaturalization, which yields a characteristic post-regulation river channel. The conceptual model was developed on the basis of the evolution of the gravel-bed river, the Raba River, during the post-regulation period in the Polish Carpathian Mountains.

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