scholarly journals EROSION DUE TO HIGH FLOW VELOCITIES: A DESCRIPTION OF RELEVANT PROCESSES

2011 ◽  
Vol 1 (32) ◽  
pp. 24 ◽  
Author(s):  
Frederik Bisschop ◽  
Paul Visser ◽  
Cees Van Rhee ◽  
Henk Jan Verhagen
Keyword(s):  
Large Scale ◽  
Analytical Formula ◽  
Sediment Concentration ◽  
Soil Mass ◽  
High Flow ◽  
Granular Soils ◽  
Erosion Process ◽  
Erosion Rates ◽  
Clear Insight ◽  
Flow Velocities

Convential models for the erosion of non-cohesive sediments overestimate the erosion rate induced by high flow velocities. These high flow velocities occur, for instance, in breaching of embankments or dunes (flow velocities up to 10 m/s) or in jetting sand with a trailing suction hopper dredger (30 to 60 m/s). At these very large flow velocities the erosion process is significantly influenced by the properties of the soil mass (non-cohesive particles). Governing parameters at higher flow velocities are dilatancy, permeability and the (un)drained shear strength of the soil. The sediment concentration in the water also influences the erosion process, especially in case of higher erosion rates. Based on the concept of Van Rhee (2007, 2010) a simple analytical formula is derived that gives a clear insight into the parameters influencing hindered erosion. The concept of hindered erosion is explained by two properties of granular soils: dilatancy and permeability. This implicates that the erosion behaviour of granular soils cannot be described by the behaviour of single particles alone. The properties of the whole soil mass should be considered in predicting erosion at higher flow velocities. Results of a large-scale breach experiment performed in 1994 in the Zwin Channel in the Netherlands (Visser, 1998) are analyzed to evaluate the formula.

scholarly journals Evaluation of Various Perimeter Barrier Products

2021 ◽  
Author(s):  
Rabin Bhattarai ◽  
◽  
Yufan Zhang ◽  
Jacob Wood ◽  
◽  
...  
Keyword(s):  
Large Scale ◽  
Sediment Concentration ◽  
Department Of Transportation ◽  
Vegetative Cover ◽  
Buffer Strip ◽  
Erosion Rates ◽  
Sediment Removal ◽  
Loam Soil ◽  
A Site ◽  
Large Scale Tests

Construction activities entail substantial disturbance of topsoil and vegetative cover. As a result, stormwater runoff and erosion rates are increased significantly. If the soil erosion and subsequently generated sediment are not contained within the site, they would have a negative off-site impact as well as a detrimental influence on the receiving water body. In this study, replicable large-scale tests were used to analyze the ability of products to prevent sediment from exiting the perimeter of a site via sheet flow. The goal of these tests was to compare products to examine how well they retain sediment and how much ponding occurs upstream, as well as other criteria of interest to the Illinois Department of Transportation. The products analyzed were silt fence, woven monofilament geotextile, Filtrexx Siltsoxx, ERTEC ProWattle, triangular silt dike, sediment log, coconut coir log, Siltworm, GeoRidge, straw wattles, and Terra-Tube. Joint tests and vegetated buffer strip tests were also conducted. The duration of each test was 30 minutes, and 116 pounds of clay-loam soil were mixed with water in a 300 gallon tank. The solution was continuously mixed throughout the test. The sediment-water slurry was uniformly discharged over an 8 ft by 20 ft impervious 3:1 slope. The bottom of the slope had a permeable zone (8 ft by 8 ft) constructed from the same soil used in the mixing. The product was installed near the center of this zone. Water samples were collected at 5 minute intervals upstream and downstream of the product. These samples were analyzed for total sediment concentration to determine the effectiveness of each product. The performance of each product was evaluated in terms of sediment removal, ponding, ease of installation, and sustainability.

scholarly journals The Debris Content of Surging Glaciers in Svalbard and Iceland

1975 ◽  
Vol 14 (72) ◽  
pp. 395-406 ◽  
Author(s):  
Chalmers M. Clapperton
Keyword(s):  
Bottom Sediments ◽  
High Flow ◽  
Frictional Heat ◽  
Horizontal Extent ◽  
Compressive Flow ◽  
Melt Water ◽  
Terminal Zone ◽  
Trigger Zone ◽  
Vertical Development ◽  
Flow Velocities

In Svalbard and Iceland there appears to be much more debris entrained in glaciers that surge than in those which do not. Conditions particularly favourable for the basal incorporation of debris develop as a consequence of the high flow velocities attained by a surge. These are increased cavitation in the lee of obstacles and an increased supply of basal melt water resulting from frictional heat and from the trigger zone. Layers of regelation ice incorporating debris can thus develop to a much greater vertical and horizontal extent than in non-surging glaciers. Excessive shearing, and the distortion of foliation structures in the terminal zone of compressive flow, enhance the vertical development of the debris-rich regelation layers. Glaciers that surge over outwash and/or fjord-bottom sediments become particularly rich in debris.

Scour Around Bridge Piers at High Flow Velocities

1980 ◽  
Vol 106 (11) ◽  
pp. 1827-1842 ◽  
Author(s):  
Subhash C. Jain ◽  
Edward E. Fischer
Keyword(s):  
High Flow ◽  
Bridge Piers ◽  
Flow Velocities

Discussion of “Scour Around Bridge Piers at High Flow Velocities”

1981 ◽  
Vol 107 (7) ◽  
pp. 958-958
Author(s):  
Fred W. Blaisdell ◽  
Clayton L. Anderson
Keyword(s):  
High Flow ◽  
Bridge Piers ◽  
Flow Velocities

Accelerated Erosion and Sedimentation in Southeast Asia

2005 ◽  
Author(s):  
Avijit Gupta
Keyword(s):  
Southeast Asia ◽  
Sediment Yield ◽  
Large Scale ◽  
Drainage Basin ◽  
High Rate ◽  
Annual Rainfall ◽  
Sediment Yields ◽  
Erosion Rates ◽  
Sediment Transfer ◽  
Very High

Periodic attempts to plot global distribution of erosion and sedimentation usually attribute most of Southeast Asia with a very high sediment yield (Milliman and Meade 1983). The erosion rates and sediment yield figures are especially high for maritime Southeast Asia. Milliman and Syvitski (1992), for example, listed 3000 t km−2 yr−1 for the archipelagos and peninsulas of Southeast Asia. They provided a number of natural explanations for the high erosion rate: location near active plate margins, pyroclastic eruptions, steep slopes, and mass movements. This is also a region with considerable annual rainfall, a very substantial percentage of which tends to be concentrated in a few months and falls with high intensity. Part of Southeast Asia (the Philippines, Viet Nam, Timor) is visited by tropical cyclones with heavy, intense rainfall and possible associated wind damage to existing vegetation. The fans at the foot of slopes, the large volume of sediment stored in the channel and floodplain of the rivers, and the size of deltas all indicate a high rate of erosion and episodic sediment transfer. This episodic erosion and sediment transfer used to be controlled for most of the region by the thick cover of vegetation that once masked the slopes. When vegetation is removed soil and regolith de-structured, and natural slopes altered, the erosion rates and sediment yield reach high figures. Parts of Southeast Asia display striking anthropogenic alteration of the landscape, although the resulting accelerated erosion may be only temporary, operating on a scale of several years. Over time the affected zones shift, and slugs of sediment continue to arrive in a river but from different parts of its drainage basin. The combination of anthropogenic alteration and fragile landforms may give rise to very high local yields. Sediment yields of more than 15 000 t km−2 yr−1 have been estimated from such areas (Ruslan and Menam, cited in Lal 1987). This is undoubtedly towards the upper extreme, but current destruction of the vegetation cover due to deforestation, expansion of agriculture, mining, urbanization, and implementation of large-scale resettlement schemes has increased the sediment yield from < 102 to > 103 t km−2 yr−1.

scholarly journals The periglacial engine of mountain erosion – Part 2: Modelling large-scale landscape evolution

2015 ◽  
Vol 3 (4) ◽  
pp. 463-482 ◽  
Author(s):  
D. L. Egholm ◽  
J. L. Andersen ◽  
M. F. Knudsen ◽  
J. D. Jansen ◽  
S. B. Nielsen
Keyword(s):  
Large Scale ◽  
Landscape Evolution ◽  
Computational Experiments ◽  
Frost Action ◽  
Erosion Rates ◽  
Bedrock Erosion ◽  
Simple Scaling ◽  
Sediment Cover ◽  
Mechanical Weathering ◽  
High Elevations

Abstract. There is growing recognition of strong periglacial control on bedrock erosion in mountain landscapes, including the shaping of low-relief surfaces at high elevations (summit flats). But, as yet, the hypothesis that frost action was crucial to the assumed Late Cenozoic rise in erosion rates remains compelling and untested. Here we present a landscape evolution model incorporating two key periglacial processes – regolith production via frost cracking and sediment transport via frost creep – which together are harnessed to variations in temperature and the evolving thickness of sediment cover. Our computational experiments time-integrate the contribution of frost action to shaping mountain topography over million-year timescales, with the primary and highly reproducible outcome being the development of flattish or gently convex summit flats. A simple scaling of temperature to marine δ18O records spanning the past 14 Myr indicates that the highest summit flats in mid- to high-latitude mountains may have formed via frost action prior to the Quaternary. We suggest that deep cooling in the Quaternary accelerated mechanical weathering globally by significantly expanding the area subject to frost. Further, the inclusion of subglacial erosion alongside periglacial processes in our computational experiments points to alpine glaciers increasing the long-term efficiency of frost-driven erosion by steepening hillslopes.

DIMENSIONAL ANALYSIS RELATIONSHIPS OF STREAMBANK EROSION RATES

2016 ◽  
Vol 78 (5-5) ◽  
Author(s):  
Azlinda Saadon ◽  
Junaidah Ariffin ◽  
Jazuri Abdullah ◽  
Norhidayati Mat Daud
Keyword(s):  
Dimensional Analysis ◽  
Physical Characteristics ◽  
Bank Failure ◽  
Erosion Process ◽  
Streambank Erosion ◽  
Fluvial Erosion ◽  
Erosion Rates ◽  
Erosion Processes ◽  
Hydraulic Force ◽  
River Meandering

Bank erosion is commonly associated with river meandering initiation and development, through width adjustment and planform evolution. It consists of two types of erosion processes; basal erosion due to fluvial hydraulic force and bank failure under the influence of gravity. Most of the studies only focused on one factor rather than integrating both factors. Evidences of previous works have shown integration between both processes of fluvial hydraulic force and bank failure. Bank failure seldom treated as a probabilistic phenomenon without assessing the physical characteristics and the geotechnical aspects of the bank. Thus, the objective of this paper is to investigate factors governing streambank erosion process and to perform a dimensional analysis considering the physical characteristics of both processes namely fluvial erosion and mass failure and their interaction.

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