Orientation of Outer Deltas
-
Upload
kiona-spence -
Category
Documents
-
view
45 -
download
4
description
Transcript of Orientation of Outer Deltas
![Page 1: Orientation of Outer Deltas](https://reader035.fdocuments.in/reader035/viewer/2022062221/56812bc7550346895d9013b7/html5/thumbnails/1.jpg)
Orientation of Outer Deltas
ALW - 05/04/2002
•Why are outer deltas formed?•What determines the orientation (of the channels)
of the outer delta + their dynamics?
•Why are outer deltas formed?•What determines the orientation (of the channels)
of the outer delta + their dynamics?
![Page 2: Orientation of Outer Deltas](https://reader035.fdocuments.in/reader035/viewer/2022062221/56812bc7550346895d9013b7/html5/thumbnails/2.jpg)
Conceptual model: •Updrift:
•Downdrift: wave-dominated
•Tide-dominated•Interaction shore parallel current and current in the strait•Preferred sediment deposition on downdrift side
Orientation of the Outer Delta:
![Page 3: Orientation of Outer Deltas](https://reader035.fdocuments.in/reader035/viewer/2022062221/56812bc7550346895d9013b7/html5/thumbnails/3.jpg)
Proposition: outer deltas are downdrift oriented w.r.t. the ‘large scale’ sediment flux
Sediment flux
•Asymmetry due to ‘external’ asymmetry only.•Hence the asymmetry in back-barrier area + alignment of islands not considered.
Hypothesis:
![Page 4: Orientation of Outer Deltas](https://reader035.fdocuments.in/reader035/viewer/2022062221/56812bc7550346895d9013b7/html5/thumbnails/4.jpg)
From process-based models + observations
M2 amplitude M2 phase
![Page 5: Orientation of Outer Deltas](https://reader035.fdocuments.in/reader035/viewer/2022062221/56812bc7550346895d9013b7/html5/thumbnails/5.jpg)
M4 amplitude M4 phase
M0 amplitudeM0 amplitude
![Page 6: Orientation of Outer Deltas](https://reader035.fdocuments.in/reader035/viewer/2022062221/56812bc7550346895d9013b7/html5/thumbnails/6.jpg)
Model Setup:
Parameters varied: •M2 amplitude (default = 1 m) + phase•M4 amplitude (default = 0 m) + phase•M0 amplitude (default = 0 m)•initial bed profile (default = flat)
![Page 7: Orientation of Outer Deltas](https://reader035.fdocuments.in/reader035/viewer/2022062221/56812bc7550346895d9013b7/html5/thumbnails/7.jpg)
M2 AmplitudeZ2=1 Z2=1 Z2=-0.4 Z2=1 Z2=-1 Z2=1
![Page 8: Orientation of Outer Deltas](https://reader035.fdocuments.in/reader035/viewer/2022062221/56812bc7550346895d9013b7/html5/thumbnails/8.jpg)
M2 Phase
degZ2=1 Z2=1
![Page 9: Orientation of Outer Deltas](https://reader035.fdocuments.in/reader035/viewer/2022062221/56812bc7550346895d9013b7/html5/thumbnails/9.jpg)
Influence of M0 Default: Z2_l = 0.9 Z2_r = 1.0 = 40 deg
Z0=0 Z0=-0.1 Z0=0 Z0=0.1
![Page 10: Orientation of Outer Deltas](https://reader035.fdocuments.in/reader035/viewer/2022062221/56812bc7550346895d9013b7/html5/thumbnails/10.jpg)
Influence of M4 phase (1)
FD
ED
FD
FD
ED
degZ4=0.2
Z4=0.2
![Page 11: Orientation of Outer Deltas](https://reader035.fdocuments.in/reader035/viewer/2022062221/56812bc7550346895d9013b7/html5/thumbnails/11.jpg)
Influence of M4 phase (2)
degZ4=0.2
Z4=0.2 FD
ED
FD
ED
![Page 12: Orientation of Outer Deltas](https://reader035.fdocuments.in/reader035/viewer/2022062221/56812bc7550346895d9013b7/html5/thumbnails/12.jpg)
Initial bed not flat
Z0=0 Z0=-0.1 Z0=0 Z0=0.1
![Page 13: Orientation of Outer Deltas](https://reader035.fdocuments.in/reader035/viewer/2022062221/56812bc7550346895d9013b7/html5/thumbnails/13.jpg)
Comparison with data
M0 amplitude Relative phase
FD
ED
: updrift (UD): downdrift (DD)
FD: downdrift (DD)ED: updrift (UD)
UD DD UD UD DD+UD
UD DD UD UD DD+UD
However: M0 seems to be more ‘efficient’
![Page 14: Orientation of Outer Deltas](https://reader035.fdocuments.in/reader035/viewer/2022062221/56812bc7550346895d9013b7/html5/thumbnails/14.jpg)
Conclusion
•Orientation of outer deltas is downdrift with respect to sediment flux•Correlates well with the Wadden Sea embayments•Initial topography changes details, not overall picture
![Page 15: Orientation of Outer Deltas](https://reader035.fdocuments.in/reader035/viewer/2022062221/56812bc7550346895d9013b7/html5/thumbnails/15.jpg)
Future work
•Add waves•Influence of shape of embayment and width of throat