Channel degradation in the middle Arve river, France

1987 ◽  
Vol 1 (2) ◽  
pp. 183-188 ◽  
Author(s):  
J.-L. Peiry
Keyword(s):  
Channel Degradation

Practical Applications of Bed Scour Calculations: Two Case Studies

2014 ◽  
Author(s):  
Leif M. Burge ◽  
Laurence Chaput-Desrochers ◽  
Richard Guthrie
Keyword(s):  
Case Studies ◽  
Flood Frequency ◽  
Flood Frequency Analysis ◽  
Accurate Estimation ◽  
Pool Depth ◽  
Regional Flood Frequency Analysis ◽  
Channel Degradation ◽  
Design Depth ◽  
Bed Scour ◽  
Over Time

Pipelines can be exposed at water crossings where rivers lower the channel bed. Channel bed scour may cause damage to linear infrastructure such as pipelines by exposing the pipe to the flow of water and sediment. Accurate estimation of depth of scour is therefore critical in limiting damage to infrastructure. Channel bed scour has three main components: (1) general scour, (2) bed degradation, and (3) pool depth. General scour is the temporary lowering of the channel bed during a flood event. Channel bed degradation is the systematic lowering of a channel bed over time. Pool depth is depth of pools below the general bed elevation and includes the relocation of pools that result from river dynamics. Channel degradation is assessed in the field using indicators of channel incision such as channel bed armoring and bank characteristics, through the analysis of long profiles and sediment transport modelling. Pool depth is assessed using long profiles and channel movement over time. The catastrophic nature of bed lowering due to general scour requires a different assessment. A design depth of cover is based on analysis of depth of scour for a given return period (eg. 100-years). There are three main steps to predict general scour: (1) regional flood frequency analysis, (2) estimation of hydraulic variables, and (3) scour depth modelling. Typically, four scour models are employed: Lacey (1930), Blench (1969), Neill (1973), and Zeller (1981), with the average or maximum value used for design depth. We provide herein case studies for potential scour for pipeline water crossings at the Little Smoky River and Joachim Creek, AB. Using the four models above, and an analysis of channel degradation and pool depth, the recommended minimum depth of cover of 0.75 m and 0.142 m, respectively, were prescribed. Variability between scour models is large. The general scour model results varied from 0.45 m and 0.75 m for the Little Smoky River and 0.16 m to 0.51 m for Joachim Creek. While these models are more than 30 years old and do not adequately account for factors such as sediment mobility, they nevertheless do provide usable answers and should form part of the usual toolbox in water crossing scour calculations.

Ongoing restoration and management of Las Vegas Wash: an evaluation of success criteria

Water Policy ◽  
2014 ◽  
Vol 16 (4) ◽  
pp. 720-738 ◽  
Author(s):  
Mahesh Gautam ◽  
Kumud Acharya ◽  
Seth A. Shanahan
Keyword(s):  
Las Vegas ◽  
Management Strategies ◽  
Management Program ◽  
Lessons Learned ◽  
Lake Mead ◽  
Channel System ◽  
Las Vegas Valley ◽  
Success Criteria ◽  
Southern Nevada ◽  
Channel Degradation

The Las Vegas Wash is a dynamic channel system that drains the Las Vegas Valley (3,950 km2) into Lake Mead and the lower Colorado River, which provides drinking water to southern California, Arizona, and southern Nevada. In the last few decades the Las Vegas Wash has undergone massive changes in terms of channel degradation and bank erosion followed by recovery and restoration efforts. The evolution of the Las Vegas Wash is interlinked with urbanization, water use, and wastewater discharge. This article reviews the historical dynamics of the Las Vegas Wash in the context of restoration: evaluates the ongoing activities in the Las Vegas Wash against an established framework and success criteria; summarizes lessons learned; and discusses challenges. The ongoing activities in the Las Vegas Wash differ from other regional restoration projects in that there is a lack of an appropriate historical reference to which restoration goals should be targeted. Keys to the success of the Las Vegas Wash restoration and management program appear to be strong interagency collaboration, funding availability, effective outreach and monitoring efforts, and adaptive management strategies based on pragmatic urban values. There is a potential for realignment of existing resources for more practical ecological restoration goals.

Upstream channel degradation triggered by a meander cutoff: Potential replacement for channel dredging

2020 ◽  
pp. 510-516
Author(s):  
K. Naito ◽  
L. Guerrero ◽  
H. Valverde ◽  
Y. Estrada ◽  
F. Fuentes ◽  
...  
Keyword(s):  
Channel Degradation

The Mammalian Urinary Bladder: It's More Than Accommodating

Physiology ◽  
1986 ◽  
Vol 1 (2) ◽  
pp. 61-65 ◽  
Author(s):  
Sk Lewis
Keyword(s):  
Urinary Bladder ◽  
Ionic Composition ◽  
Urine Volume ◽  
Regulatory System ◽  
Bladder Epithelium ◽  
Lack Of Information ◽  
Cytoplasmic Vesicles ◽  
Large Fluctuations ◽  
Channel Degradation ◽  
Function Relationship

Once tacitly assumed to be an inert sac, as evidenced by the lack of information in physiology textbooks, the mammalian urinary bladder epithelium is instead a dynamic system. We stress the structure-function relationship, which allows the bladder epithelium to accomodate large fluctuations in urine volume by orderly insertion and withdrawal of cytoplasmic vesicles. This process, coupled to a recently described hormonally regulated transport system, allows the bladder to maintain urine ionic composition nearly constant. In addition, studies on the bladder have revealed a novel regulatory system of ion transport involving channel degradation and turnover.

Uncertainty Improvement in a Simulation of Channel Evolution

2012 ◽  
Vol 212-213 ◽  
pp. 341-344
Author(s):  
Kwang Ik Son ◽  
Taik Jean Hwang ◽  
Man Ha Hwang ◽  
Young Ho Yoon
Keyword(s):  
Nakdong River ◽  
Channel Evolution ◽  
Alluvial Channel ◽  
Longitudinal Slope ◽  
Bed Materials ◽  
Channel Degradation ◽  
The Nakdong River ◽  
The Stability ◽  
Natural Channel

The Four Major Rivers Restoration Project (4MRRP), one of the largest river rehabilitation projects in Korea, has being carried out during the last three years. 0.57 billion m3 of sediment was dredged to widen and deepen the channel along four major rivers, the Han, Nakdong, Geum, and Youngsan rivers. As a result of reshaping the natural channel to a trapezoidal channel, and the construction of 16 weirs, the change of longitudinal slope of the river was inevitable. The distribution of bed materials was also changed, due to dredging. Therefore, the rivers were totally disturbed, and the stability of the rivers could not be assured. In particular, the Nakdong river, the second largest river in Korea, has the characteristics of an alluvial channel. Degradation of the main channel bed caused bank erosion, and head-cut phenomena in many tributaries. Deformations of the main channels could be observed all along the river. Long-term simulation of the channel evolution and prediction of the stability of the Nakdong river have to be examined, to cope with the instability of the river, which could lead to unexpected river disasters. This study deals with the methodology of uncertainty improvement, in analysis of the simulation and confirmation with field survey data. Methodology of uncertainty improvement in description of weir, whose discharge coefficient is unknown, in a river was suggested.

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