Impact of peak discharge increase

on the channel pattern and

dynamics of the Yellow River

Filip Schuurman

2 November 2016

26 mei 2016

The Yellow River

(Huang He)

6th Longest river in the

World (5500 km)

Large social, economic and

geographical value

Dynamic river

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Water stress in the Yellow River basin

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Water stress in the Yellow River basin

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Hydropower dams and basins

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Impact of a.o. hydropower dams

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South-North Water Transfer project

Sedimentation in the hydropower reservoirs

Water shortage, despite water storage in hydropower

reservoirs

Water transfer from wet Yangzte River basin to dry Yellow

River basin

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Research question:

How does the higher discharge affect

the channel pattern and morphodynamics

in the Yellow River?

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Methods

System analysis:

Field data

Satellite photography

Computer simulations:

Hydrodynamics + sediment transport + morphology

Calibration + validation: 1999 - 2014

Prediction future: 2015 - 2040

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Settings

Curvilinear, structured grid

2D depth-averaged

Grid resolution sufficient to capture bars

Annual hydrograph based on expected discharge

regulation scheme

Sediment inflow equal to local transport capacity

Fine sediment (0.11 mm)

Engelund-Hansen

Variable morphological factor

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Morphological factor

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Study reaches

Two study reaches of about 50 km:

Braiding

Meandering

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Braiding reach Meandering reach

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However…

First results give static channels with only

morphodynamics in first years

Dry-wet bank erosion mechanism is

insufficient

Similar to earlier studies

(e.g. Schuurman et al., 2013)

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Bank erosion in Delft3D

Dry-wet bank erosion mechanism at maximum

Boost of bank erosion by:

Strong spiral flow (Espir = 2)

Strong transverse bed slope effect (alpha = 0.2)

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Result: Braiding reach: 2000 m³/s

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Result: Braiding reach: 4000 m³/s

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Result: Meandering reach: 2000 m³/s

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Result: Bend cutoffs in meandering reach

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Result: Meandering reach

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Result: Effect on sedimentation and erosion

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Sensitivity: Bed slope parameter

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Sensitivity: Spiral flow parameterization

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Summary

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Higher (peak) discharge had large effect on the river pattern: Higher braiding intensity Transformation from meandering to braiding Severe sedimentation on the floodplains

Without mitigation measures, the transfer of water from the Yangtze River to the Yellow River is expected to have large economic and social impacts

Modelling of channel dynamics required a ‘trick’

for bank erosion, which worked well