1. Interaction of submarine canyons with
the longshore drift
Investigations of sediment bypassing rates at canyons
Researcher : Hesam Sanaee
Supervisor : Prof. J. A. Roelvink
External Supervisor : Edwin Elias, PhD, MSc
Mentor : Ali Dastgheib , PhD, MSc
WSE-HECEPD 2011-2013

2. Content of Presentation
 Introduction
 Research objective
 Research methodology
 Model setup in 2DH
 Forcing
 Model Simulation
 Analysis of residual current
 Analysis of the long shore rates
 Conclusion and recommendations

3. Introduction
Area of Study
Santa Barbara Littoral Cell

4. Introduction
Tidal Information
A diurnal tide with a strong semi-diurnal distortion
Diurnal Range = 1.64m
Tidal velocities < 5 cm/s

5. Introduction
Wave Climate
Wave directions range from 105°N to 345°N,
No waves coming from 345N or more, due to the
sheltering of Point Conception
More than 70% of waves within dataset
originated from the west/north-western (270 -
345)
Wave heights ranging from 0.5 - 8.0m and
waves higher than 7 m occurs rarely

6. Introduction
Problem Statement
Several large canyons connect to the SBLC coastal system and
(are assumed) to cause a loss of sediment from the coastal zone
For a sustainable coastal management, it is necessary to:
–Understand the sediment transports around canyons

7. Main objective
 To determine the quantity of littoral drift bypassing the submarine canyons versus the
amount captured by the canyon
What is the role of sediment delivery due to the littoral sediment transport?
What are the dominant processes in driving the hydrodynamics and sediment transport?
Process-based model consist of the following tasks
1. Hydrodynamic modelling; how do flow patterns in a canyon look like?
2. Sediment transport modelling; how do the sediment transports over a canyon look like?
3. How does the canyon modify the wave propagation patterns?
4. What are the littoral drift rates along the coast with and without presence of the submarine canyons?
Research objectives

8. In order to answer the objective of this research study, the following procedures was
performed
o Using a 2DH model of SBLC
Extending the sediment budget analysis to the point Mugu
Investigating the effect of the Hueneme and Mugu canyons on the littoral drift
Investigating the different geometries with and without canyons
o On a 3D model of Mugu submarine canyon
 Investigating the hydrodynamic patterns and processes
 Compare the Z-model with Sigma-Model
Research methodology

9. Model setup in 2DH
Delft3D-Wave Module
•Low resolution wave grid 180km x 90km + High
resolution grid at nearshore
•Cross-shore resolution of 1100m -550 m
(nearshore)
•Longshore resolution is about 1100 m
•In total 22,800 grid points (151 in both M and N
direction)
Delft3D-Flow Module
•Higher resolution flow grid 130km x12km
•Cross-shore resolution of 550m(seaward
boundary) to 30 m (nearshore)
•Longshore resolution is about 600 m (western
boundary) to 60m (eastern boundary)
•In total 60,965 grid points (M=685, N=89)
•Neumann boundaries at Cross-shore boundaries
in combination of water level in offshore
boundary
•Hydrodynamic time step = 15 seconds

10. Forcing
Input reduction of the hydrodynamic forcing
•Schematization of tide
A morphological tide (HW-LW cycle)
1.1x the mean tide
Constituent Description Amplitude [m]
Angular frequency
[deg/hr]
M2 Principal lunar semi-diurnal const. 0.5163 28.993289
K1 Lunisolar diurnal const. 0.3704 14.496644
O1 Lunar diurnal const. 0.2404 14.496644
Morphological tidal constituents with their adjusted amplitude and angular frequency

11. Forcing
Input reduction of the hydrodynamic forcing
•Schematization of wave climate
•Wave buoys data
3 years of wave record

12. 105-120 120-135 135-150 150-165 165-180 180-195 195-210 210-225 225-240 240-255 255-270 270-285 285-300 300-315 315-330 330-345
0,00 - 1,50 0.00098 0.00218 0.00738 0.02668 0.05485 0.06596 0.00467 0.00314 0.00216 0.00195 0.00319 0.01514 0.02835 0.03914 0.00887 0.00011 0.26
1,50 - 2,00 0.00008 0.00021 0.00078 0.00128 0.00187 0.00232 0.00277 0.00165 0.00150 0.00186 0.00368 0.02188 0.05631 0.10207 0.02323 0.00035 0.22
2,00 - 2,50 0.00008 0.00008 0.00008 0.00018 0.00016 0.00026 0.00059 0.00035 0.00066 0.00074 0.00271 0.02023 0.06377 0.09758 0.02034 0.00003 0.21
2,50 - 3,00 0.00000 0.00000 0.00016 0.00029 0.00010 0.00026 0.00030 0.00018 0.00021 0.00035 0.00133 0.01168 0.04511 0.06465 0.01388 0.00002 0.14
3,00 - 3,50 0.00000 0.00000 0.00005 0.00005 0.00005 0.00006 0.00013 0.00010 0.00018 0.00013 0.00048 0.00632 0.02606 0.04104 0.00699 0.00005 0.08
3,50 - 4,00 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00002 0.00000 0.00000 0.00002 0.00022 0.00351 0.01305 0.02103 0.00407 0.00000 0.04
4,00 - 4,50 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00002 0.00000 0.00000 0.00155 0.00619 0.01148 0.00229 0.00000 0.02
4,50 - 5,00 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00003 0.00086 0.00277 0.00563 0.00102 0.00000 0.01
5,00 - 5,50 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00002 0.00038 0.00134 0.00250 0.00050 0.00000 0.00
5,50 - 6,00 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00026 0.00098 0.00190 0.00030 0.00000 0.00
6,00 - 6,50 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00006 0.00013 0.00040 0.00112 0.00019 0.00000 0.00
6,50 - 7,00 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00003 0.00032 0.00034 0.00006 0.00000 0.00
7,00 - 7,50 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00008 0.00014 0.00003 0.00000 0.00000 0.00
7,50 - 8,00 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00003 0.00003 0.00000 0.00000 0.00000 0.00
SUM 0.00 0.00 0.01 0.03 0.06 0.07 0.01 0.01 0.00 0.01 0.01 0.08 0.24 0.39 0.08 0.00 1.00
Mean Wave Hight Hs (m)
Wave direction sector (degrees w.r.t. North)
Probability of Occurance (%)
SUM
Forcing
Input reduction of the hydrodynamic forcing
•Schematization of wave climate
•Wave classification (116 wave conditions)

13. Forcing
Input reduction of the hydrodynamic forcing
•Schematization of wave climate
•Reduction of wave climate
•Opti Method
selects an optimum subset of wave conditions that contributes more to the mean total sediment
transport, only trough a number of predefined transects
•Energy Flux
selects an optimum subset of wave conditions that has equal energy with the total wave record

14. Forcing
Input reduction of the hydrodynamic forcing

15. Forcing
Input reduction of the hydrodynamic forcing
116 simulations with different wave
conditions
Each simulation has a certain
influence on the long shore transport

16. Forcing
Input reduction of the hydrodynamic forcing
• Opti-Method
Reduction
116 ---> 24
RMS error < 5%
WC Hs (m) Tp (s) Dir (°) Old Weight New Weight
South/South-eastern
4 0.95 14.22 159.28 0.0267 0.0359
5 0.94 14.36 173.71 0.0549 0.0959
19 1.68 10.34 144.53 0.0008 0.0011
6 0.92 14.38 187.89 0.0660 0.1134
24 1.7 15.04 217.84 0.0016 0.0007
West/Northwest
25 1.71 14.37 233.39 0.0015 0.0029
11 1.21 12.96 263.5 0.0032 0.0044
27 1.75 13.3 263.81 0.0037 0.0072
12 1.27 12.03 278.58 0.0151 0.0256
85 4.21 14.6 279.21 0.0016 0.0028
28 1.77 12.78 279.27 0.0219 0.0264
80 3.71 14.68 280.23 0.0035 0.0021
45 2.25 12.83 293.58 0.0638 0.1248
73 3.23 13.92 293.79 0.0261 0.0129
81 3.72 14.12 293.99 0.0130 0.0075
14 1.31 9.32 308.08 0.0391 0.0415
82 3.73 12.3 308.14 0.0210 0.0282
60 2.74 11.02 308.18 0.0646 0.0693
74 3.23 11.69 308.22 0.0410 0.0752
87 4.22 12.24 308.35 0.0115 0.0066
46 2.24 10.11 308.41 0.0976 0.1925
101 5.75 13.07 308.96 0.0019 0.0032
83 3.74 10.99 319.18 0.0041 0.0046
15 1.29 8.49 319.56 0.0089 0.0012

17. Forcing
Input reduction of the hydrodynamic forcing
•Schematization of wave climate
•Energy Flux

18. Forcing
Input reduction of the hydrodynamic forcing
•Schematization of wave climate
•Reduction of wave climate
•Energy flux
WC Hs (m) Tp (s) Dir (°) Occ (%) Total %
South/South-eastern
9 1.53 13.04 157.6 1.11
2 0.8 14.1 160.2 3.73
5 1.08 14.44 161.1 2.03
1 0.79 14.07 182 3.87
7 1.45 14.49 182 1.11
4 1.05 14.59 182.1 2.13
3 0.93 14.33 195.1 2.73
6 1.44 14.91 206.1 1.1
14 2.13 14.48 211.1 0.52 18.33
West/Northwest
8 1.49 13.38 255.8 1.15
15 2.25 13.8 259.1 0.49
20 3.29 14.03 260.2 0.22
10 1.88 12.72 284.4 11.69
22 4.23 14.75 285.5 1.99
16 2.86 13.91 285.6 4.63
17 2.97 13.33 297.6 4.47
12 1.99 11.82 297.6 11.29
21 4.21 13.94 298 2.12
13 1.99 10.07 306.2 13.17
19 3.04 11.75 306.2 4.86
23 4.35 12.7 306.4 2.19
24 4.39 11.74 315 2.32
18 3 10.28 315.1 5.69
11 1.95 8.98 315.2 15.38 81.66

19. Forcing
Input reduction of the hydrodynamic
forcing
• The energy flux method resembles better
percentage of the total target
24 wave cases from WEF are the
reduced wave climate

20. Model simulation
Model simulations was performed separately for each wave condition
(24 wave conditions from selected wave cases) -On Deltares cluster
Delft3D = Version 5.01.00.2163
Run time = over one tidal cycle of 1490 minutes
Transport formula = Van Rijn 1993 by default
Bed updating = Turned off (maximum longshore transport)

21. Analysis of residual current
Residual current is determined
by Fourier analysis of the
velocity field
Accounting for both effect of
tides and waves
Residual current results from
the weighted average of the
mean velocities of all 24 wave
cases

22. Analysis of residual current Section 1

23. Analysis of residual current
Section 3

24. Analysis of the longshore rates
Longshore drift rates
Less than 10% error in annual
dredging rates for two bench
mark
Transect 12 Santa Barbara
harbor
Transect 24 Ventura harbor
Canyons

25. Analysis of the longshore rates
Individual wave case contribution to the
annual sediment transport
Longshore sediment transport is a function of wave
height and direction (according to the CERC formula)

26. Analysis of the longshore rates
Littoral drift rates along the coast with and without canyons

27. Analysis of the longshore rates
Littoral drift rates along the coast with and without canyons
Potential sediment
lost to the canyons
? Canyons

28. Analysis of the longshore rates
Individual wave case contribution to the
annual sediment transport
With canyons
Southern Swells

29. Analysis of the longshore rates
Littoral drift rates along the
coast without canyons
Wave case 4 ( Dir 182 degree)

30. Analysis of the longshore rates
Littoral drift rates along the
coast without canyons
Wave case 4 ( Dir 182 degree)

31. Analysis of the longshore rates
Littoral drift rates along
the coast without canyons
•Effect of each canyon

32. Conclusion
 The quantity of littoral drift bypassing the submarine canyons vs. the amount captured by
the canyon
The dominant processes in driving the hydrodynamics and sediment transport
•Dominant westerly swells induce a net increasing eastward sediment transport, except upcoast of the
Hueneme canyon due to coastline orientation and presence of the Hueneme canyon
•Southern waves drives the sediment transport westward and net sediment transport along the up
coast of the canyons increases due to the refraction over the canyons
The role of sediment delivery due to the littoral sediment transport
•The longshore sediment transport analysis estimates the potential lost to the canyons
Recommendations
•Using a real forces could validate the observed hydrodynamic data (in between two canyons)
•The 3D Model of each canyons could resolve the sediment movement in the canyons

33. Thank you
and
Questions ?