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

2

26 mei 2016

Water stress in the Yellow River basin

3

26 mei 20164

Water stress in the Yellow River basin

26 mei 2016

Hydropower dams and basins

5

26 mei 20166

Impact of a.o. hydropower dams

26 mei 2016

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

7

26 mei 2016

Research question:

How does the higher discharge affect the channel pattern and morphodynamics

in the Yellow River?

8

26 mei 2016

Methods

� System analysis:� Field data� Satellite photography

� Computer simulations:� Hydrodynamics + sediment transport + morphology� Calibration + validation: 1999 - 2014� Prediction future: 2015 - 2040

9

26 mei 2016

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

10

26 mei 2016

Morphological factor

11

26 mei 2016

Study reaches

� Two study reaches of about 50 km:

� Braiding

� Meandering

12

Braiding reach Meandering reach

26 mei 201613

26 mei 2016

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)

14

26 mei 2016

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)

15

26 mei 2016

Result: Braiding reach: 2000 m³/s

26 mei 2016

Result: Braiding reach: 4000 m³/s

26 mei 201618

26 mei 201619

Result: Meandering reach: 2000 m³/s

26 mei 2016

Result: Bend cutoffs in meandering reach

20

26 mei 2016

Result: Meandering reach

21

26 mei 2016

Result: Effect on sedimentation and erosion

22

26 mei 2016

Sensitivity: Bed slope parameter

23

26 mei 2016

Sensitivity: Spiral flow parameterization

24

26 mei 2016

Summary

25

� 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