uniqueness and generality of delta morphologoy

1. 1Challenge the future
Uniqueness and generality of
delta morphology
The effect of initial bathymetry perturbations on long-
term morphological modeling
Liang Li
Helena van der Vegt
Joep Storms
Dirkjan Walstra

2. 2Challenge the future
Introduction
Validity of Process-based long-term
models
Long-term: Unknown initial and boundary conditions

3. 3Challenge the future
Introduction
Uncertainties
1. Model assessment
2. Sensitivity analysis
3. Geometry population

4. 4Challenge the future
Introduction
Objective
1. Develop a series of indicators for Delft3d models to calculate the
geometry of the morphological patterns.
2. Quantify the effect initial bathymetry perturbations on the delta
morphology

5. 5Challenge the future
Indicators
Why
Ombrone system, Italy Frontera system, Tabasco,
Mexico

6. 6Challenge the future
Indicators
Compare delta morphologies
Point-wise
metric Pattern
recognitionShort time scale
Long time scale

7. 7Challenge the future
Indictors
List

8. 8Challenge the future
Indictors
Channel network, delta plain geometry
Delta plain Channel network

9. 9Challenge the future
Model setup
Model grid and bathymetry
Model parameters Value Unit
Manning 0.03 1
3
s m
Sand diameter 0.00025 m
Sand drydensity 1600 3
kg m
Clayfallingvelocity 0.0015 1
ms
Claydry density 500 3
kg m
Critical shearstressforclay erosion 0.5 2
N m
Morphological accelerationfactor 30 [ - ]

10. 10Challenge the future
Model setup
Initial bathymetry perturbations
1. 1cm perturbations
2. 1000 m3 river discharge
3. 1 m wave height
4. 1 m tidal amplitude

11. 11Challenge the future
Morphology
Initial bathymetry noise
Unperturbed

12. 12Challenge the future
Results
Delta plain

13. 13Challenge the future
Mean
b 0.16%
c -0.22%
d 0.13%
Mean
b 0.2%
c 2.6%
d 2.7%

14. 14Challenge the future
Results
Channel networks

15. 15Challenge the future
Mean
B 5%
C 7%
D 7.6%
Mean
B 24%
C 33%
D 24%

16. 16Challenge the future
Conclusions(1)
1. The difference induced by small perturbations does not increase in
time.

17. 17Challenge the future
Conclusions(2)
1. The uncertainty range induced by small perturbations
varies for different scale of indicators.
1. Small: delta plain
2. Large: channel network