msc thesis final1

Interaction of submarine canyons with the longshore driftInvestigations of sediment bypassing rates at canyons

Researcher : Hesam SanaeeSupervisor : Prof. J. A. RoelvinkExternal Supervisor : Edwin Elias, PhD, MScMentor : Ali Dastgheib , PhD, MSc

WSE-HECEPD 2011-2013

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

IntroductionArea of Study

Santa Barbara Littoral Cell

IntroductionTidal Information

A diurnal tide with a strong semi-diurnal distortionDiurnal Range = 1.64m Tidal velocities < 5 cm/s

IntroductionWave 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

IntroductionProblem 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

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

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

Model setup in 2DHDelft3D-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

ForcingInput 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


• Schematization of wave climate • Wave buoys data

3 years of wave record

105-120 120-135 135-150 150-165 165-180 180-195 195-210 210-225 225-240 240-255 255-270 270-285 285-300 300-315 315-330 330-3450,00 - 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 0.261,50 - 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 0.222,00 - 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 0.212,50 - 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 0.143,00 - 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 0.083,50 - 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 0.044,00 - 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 0.024,50 - 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 0.015,00 - 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 0.005,50 - 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 0.006,00 - 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 0.006,50 - 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 0.007,00 - 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 0.007,50 - 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


• Schematization of wave climate • Wave classification (116 wave conditions)


• Schematization of wave climate • Reduction of wave climate

• Opti Methodselects an optimum subset of wave conditions that contributes more to the

mean total sediment transport, only trough a number of predefined transects

• Energy Fluxselects an optimum subset of wave conditions that has equal energy with the

total wave record


116 simulations with different wave conditions

Each simulation has a certain influence on the long shore transport


• Opti-Method

Reduction116 ---> 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


• Schematization of wave climate • Energy Flux


• 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 3.735 1.08 14.44 161.1 2.03

1 0.79 14.07 182 3.87

7 1.45 14.49 182 1.114 1.05 14.59 182.1 2.13

3 0.93 14.33 195.1 2.736 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 1.1515 2.25 13.8 259.1 0.49

20 3.29 14.03 260.2 0.22

10 1.88 12.72 284.4 11.6922 4.23 14.75 285.5 1.99

16 2.86 13.91 285.6 4.63

17 2.97 13.33 297.6 4.4712 1.99 11.82 297.6 11.29

21 4.21 13.94 298 2.12

13 1.99 10.07 306.2 13.1719 3.04 11.75 306.2 4.86

23 4.35 12.7 306.4 2.19

24 4.39 11.74 315 2.3218 3 10.28 315.1 5.69

11 1.95 8.98 315.2 15.38 81.66


• The energy flux method resembles better percentage of the total target

24 wave cases from WEF are the reduced wave climate

Model simulationModel 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)

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

Analysis of residual current Section 1

Analysis of residual currentSection 3

Analysis of the longshore ratesLongshore drift rates

Less than 10% error in annual dredging rates for two bench mark

Transect 12 Santa Barbara harbor

Transect 24 Ventura harborCanyons

Analysis of the longshore ratesIndividual wave case contribution to the annual sediment transport

Longshore sediment transport is a function of wave height and direction (according to the CERC formula)

Analysis of the longshore ratesLittoral drift rates along the coast with and without canyons

Analysis of the longshore ratesLittoral drift rates along the coast with and without canyons

Potential sediment lost to the canyons

? Canyons

Analysis of the longshore ratesIndividual wave case contribution to the annual sediment transport

With canyons

Southern Swells

Analysis of the longshore ratesLittoral drift rates along the coast without canyons

Wave case 4 ( Dir 182 degree)

Analysis of the longshore ratesLittoral drift rates along the coast without canyons

• Effect of each canyon

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

Thank you and

Questions ?

msc thesis final1

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