dsd-int 2015 - uniqueness and generality of delta morphologoy - liang li

1 Challenge 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


Introduction Validity of Process-based long-term

models

Long-term: Unknown initial and boundary conditions


Introduction Uncertainties

1. Model assessment

2. Sensitivity analysis

3. Geometry population


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


Indicators Why

Ombrone system, Italy Frontera system, Tabasco, Mexico


Indicators Compare delta morphologies

Point-wise metric Pattern

recognition Short time scale

Long time scale


Indictors List


Indictors Channel network, delta plain geometry

Delta plain Channel network


Model setup Model grid and bathymetry

Model parameters Value Unit

Manning 0.03 1

3s m

Sand diameter 0.00025 m

Sand dry density 1600 3kg m

Clay falling velocity 0.0015 1ms

Clay dry density 500 3kg m

Critical shear stress for clay erosion 0.5 2N m

Morphological acceleration factor 30 [ - ]


Model setup Initial bathymetry perturbations

1. 1cm perturbations 2. 1000 m3 river discharge 3. 1 m wave height 4. 1 m tidal amplitude


Morphology Initial bathymetry noise

Unperturbed


Results Delta plain


Mean

b 0.16%

c -0.22%

d 0.13%

Mean

b 0.2%

c 2.6%

d 2.7%


Results Channel networks


Mean

B 5%

C 7%

D 7.6%

Mean

B 24%

C 33%

D 24%


Conclusions(1)

1. The difference induced by small perturbations does not increase in time.


Conclusions(2)

1. The uncertainty range induced by small perturbations varies for different scale of indicators. 1. Small: delta plain 2. Large: channel network

dsd-int 2015 - uniqueness and generality of delta morphologoy - liang li

Software