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EAH 422 ADVANCED WATER RESOURCES ENGINEERING
Stable Channel HydraulicsProf. Aminuddin Ab. Ghani
W e l e a dReferences
Howard H. Chang (1988)
W e l e a dSediment Transport
Welcome to the Book Companion Site forNalluri & Featherstone’s Civil Engineering Hydraulics: Essential Theory with Worked Examples, 6th Editionby Martin Marriott
http://www.wiley.com//legacy/wileychi/marriott/
978‐1‐118‐91563‐9Paperback472 pagesApril 2016, Wiley‐Blackwell
W e l e a dConstructed Meandering River
Compound Channel with Meandering Main Channel
W e l e a dRiver with Floodplains
Flood PlainFlood Plain
Main Channel
W e l e a dCrossing
W e l e a dMain Channel with Dry Floodplain
W e l e a dInundated Floodplain
W e l e a dRebuilding Meanders
• Analysis of river behavior has found that stable channelsgenerally follow a meander pattern.
• Where channels have been straightened, such as in a drainagechannel, over time the flow can often be observed to rebuildthe meander pattern. Sediment is deposited in the lowvelocity zone in the inner meander and eroded from theopposite bank as flow accelerates around the outer bend.
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Schematic channel pattern and profile
Many rivers follow a naturally undulating profile
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Schematic meandering channel pattern
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Rebuilding Menders from Straight Channel
W e l e a dRiver with Floodplains
Flood Plain
Flood Plain
Main Channel
Bund
2 April 2015
W e l e a dRiver with Floodplains
Riffle & Pool
Riffle
Pool
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B = 5.04 m
Channel Cross Section 1
W e l e a dBenefits of Pools and Riffles
• Riffles, snags and other channel controls are important to the stability andecology of stream systems.
• The pool‐riffle sequence provides a variety of riverine habitats that areable to support a greater diversity of species than sections that haveuniform characteristics.
• Riffles and meanders create variable water speeds and depths andmaintain river pools that are important in providing warm weather refugesand breeding areas. The pools also provide resting zones for migratingaquatic fauna after tackling higher velocity flows.
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• Pool‐riffle sequences contribute to channel stability by controlling thevelocity of flow and reducing the downstream movement of sedimentsinto the river.
• Stabilized bed material is important for the establishment of instreamvegetation and habitat for aquatic fauna. Sediment accumulates behindthe riffle and vegetation can be established on the flanks, stabilizing thebanks.
• By locking the sediment and reducing flow velocities, nutrients in thewater column can be removed through biological processes or remainbound in the bed material.
Benefits of Pools and Riffles
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• Water quality is also improved as the riffle creates turbulence that aeratesthe water, which in turn supports microbial activity that breaks downorganic matter and assimilates nutrients.
• A riffle structure can be designed to provide a livestock watering orcrossing point.
• The pool created by the riffle can be used for livestock watering or tosupply, via a pump, an off‐stream tank or trough.
Benefits of Pools and Riffles
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Stable Channel Design Methods• Available Methods:
• Tractive Force Method
– Based on shear stress
– No sediment transport occurs
• Permissible Velocity Method
– Based on allowable velocity
– No sediment transport occurs
• Regime equations
– Based on relationships for depth, width and slope
– Common relationships: Lacey, Blench
– * Sediment transport occurs
• Rational Method
– Based on sediment transport equations
– Sediment transport occurs
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Stable Channel Design with No Sediment Transport
• Stable channel criteria
‐ Shear stress
‐ Permissible velocity
0 < c
V0 < Vc
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Critical Bed Shear Stress: Shields Diagram
© USM_REDAC_2009
Critical Bed Shear Stress (cb): Shields Diagram
(d50 = 4mm)
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Critical Shear Stress at banks
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Flow Shear Stress Distributions
W e l e a dFlow Shear Stress Distributions
W e l e a dPermissible Velocity
W e l e a dPermissible Velocity
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Allowable velocity and shear stress for selected lining materials
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Reinforced Erosion Control Product Applications
Installation of TRM for Kulim HiTech Project
W e l e a dStable Channel Assessment
W e l e a dStable Channel Assessment
W e l e a dChannel Cross Section 2
W e l e a dShear Stress Design Method
W e l e a dPermissible Velocity Design Method
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Stable Channel Design with Sediment Transport
• Blench Regime Method
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• Sediment Transport Method
Stable Channel Design with Sediment Transport
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Observed and stable channel configurations
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Observed and stable channel configurations
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Observed and stable channel configurations
W e l e a dChannel Stability Modeling
Major Steps ofComputation forFLUVIAL‐12 Model
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Case Study: Sediment Transport in Kulim River
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Case Study: Sediment Transport in Kulim River
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Case Study: Sediment Transport in Kulim River
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Case Study: Sediment Transport in Kulim River
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Case Study: Sediment Transport in Kulim River
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Case Study: Sediment Transport in Kulim River
2003 Flood
100‐yr Flood
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Modeled Profile Changes before and after October 2003 Flood
Case Study: Sediment Transport in Kulim River
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Case Study: Sediment Transport in Kulim River
Modeled Cross Section Changes before and after October 2003 Flood
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Case Study: Sediment Transport in Kulim River
Modeled Profile Changes up to 2016
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