Presentation by Torsten Heyer (TU Dresden) at the Delft3D User Days, during Delft Software Days 2016. Wednesday 2 November 2016, Delft.

1. Investigation of sediment transport
processes in mine pit lakes induced by
wind waves
Delft3D - User Days
Torsten Heyer & Carsten Schulz
Faculty of Civil Engineering Institute of Hydraulic Engineering and Technical Hydromechanics
Delft, November 2nd, 2016

2. Outline
• Introduction
• Model setup
• Results
• Summary & perspectives
Delft, 02/11/2016 Sediment transport in mine pit lakes Slide 2 of 21

3. Introduction
Model setup
Results
Summary &
perspectives
Introduction
Delft, 02/11/2016 Sediment transport in mine pit lakes
source: www.sitemap.de
Slide 3 of 21
Lusatia

4. Introduction
Model setup
Results
Summary &
perspectives
Introduction
Delft, 02/11/2016 Sediment transport in mine pit lakes
source: www.umweltveraendern.de
Slide 4 of 21

5. Introduction
Investigation area
Delft, 02/11/2016 Sediment transport in mine pit lakes
• former Lusatia brown coal mining area near Cottbus
• open-cast pits – ongoing flooding to create lakes for
recreational purposes  establishment of tourism industry
Lake Meuro
Introduction
Model setup
Results
Summary &
perspectives
Slide 5 of 21

6. Delft, 02/11/2016 Sediment transport in mine pit lakes
• Flooding period:
2007-2017
• Final water level:
100,50 m NHN
• Maximum depth:
≈ 50 m
• Main wind direction:
o W – SW
• Fetch length:
o NW-SO ≈ 5,1 km
o NO-SW ≈ 2,5 km
Lake Meuro, current and final (red) water level
[source: Google Earth, 2015]
Introduction
Lake Meuro
Introduction
Model setup
Results
Summary &
perspectives
Slide 6 of 21

7. Delft, 02/11/2016 Sediment transport in mine pit lakes
• Stability of bank slopes
(fine-grained
excavation material)
• Erosion and
deposition of
sediments (inlets,
marinas)
 long- and cross-
shore transport
• Acidification due to
pyrit activation (waves,
groundwater inflow)
...and many more
Lake Meuro, current and final (red) water level
[source: Google Earth, 2015]
Introduction
Challenges
Introduction
Model setup
Results
Summary &
perspectives
 numerical simulations using Delft3D (WAVE & FLOW)
Slide 7 of 21

8. Model Setup
Computational grids
Storm simulation Long-term simulation
Wave forecast
Vertical discretization (s-Layer, 15)
Delft, 02/11/2016 Sediment transport in mine pit lakes
Introduction
Model setup
Results
Summary &
perspectives
source: Delft3D manual
Slide 8 of 21

9. • WSP=94/98/100,5 m NHN
WSP=94 mNHN
WSP=98 mNHN WSP=100,5 mNHN
Model Setup
Bathymetry & shoreline
Delft, 02/11/2016 Sediment transport in mine pit lakes
Introduction
Model setup
Results
Summary &
perspectives
Slide 9 of 21

10. • Base data: samples along the shoreline
Model Setup
Sediment data
Region D50
[mm]
Sediment 1 0,175
Sediment 2 0,212
Sediment 3 0,405
• Non-cohesive
material
• Soil types:
o SU
o SU*/ST
o SE
Delft, 02/11/2016 Sediment transport in mine pit lakes
Introduction
Model setup
Results
Summary &
perspectives
Slide 10 of 21

11. • Revetment zones  no erosion; deposition possible
Model Setup
Sediment data
Delft, 02/11/2016 Sediment transport in mine pit lakes
Introduction
Model setup
Results
Summary &
perspectives
Slide 11 of 21

12. • Simulation (WSP=100,5 m NHN) of:
• Storm event (Tn=20 years)  design parameters (revetments, etc.)
• 1 year wind event (year 1990; measured)  long-term sediment
transport
• Storm event: w10.20a= 29,2 m/s (steady wind field)
• Wind year: w10.max= 18,2 m/s (unsteady wind field)
Delft, 02/11/2016 Sediment transport in mine pit lakes
Model Setup
Wind data
0
5
10
15
20
25
30
35
0° 60° 120° 180° 240° 300° 360°
W10[m/s]
Direction
T = 1a
T = 2a
T = 5a
T = 10a
T = 20a
T= 100a
Introduction
Model setup
Results
Summary &
perspectives
Slide 12 of 21

13. Model Setup
Transport formula
Delft, 02/11/2016 Sediment transport in mine pit lakes
Introduction
Model setup
Results
Summary &
perspectives
Slide 13 of 21

14. Model Setup
Transport formula
Delft, 02/11/2016 Sediment transport in mine pit lakes
• Best fit: Bijker (1971); also tested: van Rijn, Soulsby
Introduction
Model setup
Results
Summary &
perspectives
Slide 14 of 21

15. • Example: WSP 98,0 m NHN; 260°; w10,20a=29,2 m/s; tE=2,5h
Results
Wave forecast
Delft, 02/11/2016 Sediment transport in mine pit lakes
Introduction
Model setup
Results
Summary &
perspectives
Slide 15 of 21

16. • Example: WSP 98,0 m NHN; long-term simulation (year 1990)
• Calculation of total transported volume and check of volume balance
Results
Erosion/deposition
Delft, 02/11/2016 Sediment transport in mine pit lakes
erosion deposition
Introduction
Model setup
Results
Summary &
perspectives
Slide 16 of 21

17. • Example: WSP 98,0 m NHN; Long-term simulation (year 1990)
Results
Erosion/deposition
Delft, 02/11/2016 Sediment transport in mine pit lakes
Introduction
Model setup
Results
Summary &
perspectives
Slide 17 of 21

18. • Example: WSP 98,0 m NHN; Long-term simulation (year 1990)
Results
Sediment transport rate
Delft, 02/11/2016 Sediment transport in mine pit lakes
Introduction
Model setup
Results
Summary &
perspectives
Slide 18 of 21

19. • Effects of piers and floating breakwaters
Wave height, KZ, 260° Erosion/Deposition, LZ
without
measures
with
measures
Results
Examination of variants
Delft, 02/11/2016 Sediment transport in mine pit lakes
Introduction
Model setup
Results
Summary &
perspectives
Slide 19 of 21

20. • Wind-induced sediment transport (longshore, cross-shore)
could be simulated by Delft3D (Wave/Flow)
Summary & perspectives
Delft, 02/11/2016 Sediment transport in mine pit lakes
Introduction
Model setup
Results
Summary &
perspectives
Further investigations planned regarding:
• appropriate transport formula
(validation of the physical model test in wave flume)
• Possibility of model calibration
(recalculation of an eroding shoreline over 6 years)
• Water quality issues
Questions/tasks:
• Reduction of computational effort (time) for long-term
simulations (subgrids, scale factor, …)
• Mixed sediments  effect of decomposition
• (result) file size reduction (preselected parameters only?)
Slide 20 of 21

21. Delft, 02/11/2016 Sediment transport in mine pit lakes
Slide 21 of 21

22. Thank you
for your attention!
Technische Universitaet Dresden
Institute of Hydraulic Engineering and Technical Hydromechanics (IWD)
August-Bebel-Straße 30
01219 Dresden
Germany
: +49-(0)351-463 33874
: +49-(0)351-463 37120
: https://tu-dresden.de/bu/bauingenieurwesen/iwd
: torsten.heyer@tu-dresden.de
Delft, 02/11/2016 Sediment transport in mine pit lakes

23. Grid parameters Unit Morphodynamics Wave prediction
Storm
simulation
Long-term
simulation
Number of M-nodes 152 73 51
Number N-nodes 302 138 101
minimum Area [m²] 45 114 943
mean Area [m²] 386 1.417 3.431
maximum Area [m²] 665 5.000 7.961
Number of nodes 45.904 10.074 5.151
Number of elements 32.075 8.446 5.000
Model Setup
Computational grids
Delft, 02/11/2016 Sediment transport in mine pit lakes
Introduction
Model setup
Results
Summary &
perspectives
Slide 23

24. Model Setup
Transport formula
Delft, 02/11/2016 Sediment transport in mine pit lakes
• Best fit: Bijker (1971); also tested: van Rijn, Soulsby
Introduction
Model setup
Results
Summary &
perspectives
Slide 24