Presentation by Edwin Elias, Deltares USA, at the Delft3D and XBeach User Day: Coastal morphodynamics, during Delft Software Days - Edition 2019. Wednesday, 13 November 2019, Delft.

1. 'SPIT: APPLICATION OF A NOVEL SEDIMENT
PATHWAY VISUALIZATION METHOD’
A CASE-STUDY FOR THE NORTH-HEAD DISPOSAL SITE,
COLUMBIA RIVER, USA
Edwin Elias, Stuart Pearson, Andrew Stevens & Maarten van Ormondt
D e l f t 3 D U s e r D a y s 2 0 1 9

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WHY?
1) Visualizations are a great way to explain
complex flow and sediment transport
patterns
2) Visualizations are a great way to understand
complex flow and sediment transport
patterns
3) Visualizations are a great way to engage
stakeholders
Let’s develop a method to do this for sediment
transport and sediment transport pathways.

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It is SPIT, because it is
not a Sediment Tracer!
Sediment
Pathways
Interactive
visualisation
Tool

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Columbia River (USA)
PacificOcean
Oregon
Washington

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Columbia River (USA)
PacificOcean
Oregon
Washington

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PacificOcean
Objectives
1) Large dredge efforts in the
Mouth of the Columbia
River to maintain the
Federal Navigation
Channel (4,5-6 million m3)
2) Strong erosion observed at
Benson Beach.
3) There is a need to keep
sediment in the Littoral
Cell.
4) Strategic placement in
shallow water disposal
sites.

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North Head nearshore
circulation and transport
pathways modeling
Objectives
1) Quantify the sediment linkages between the MCR,
North Head shallow water disposal site, and the
adjacent open coast beaches
2) Provide guidance on strategic placement of dredged
material within the North Head permit area
Not a trivial task using standard methods.
Can we use SPIT analysis?

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North Head nearshore
circulation and transport
pathways modeling
Objectives
1) Quantify the sediment linkages between the MCR,
North Head shallow water disposal site, and the
adjacent open coast beaches
2) Provide guidance on strategic placement of dredged
material within the North Head permit area
Method
1. Extensive Field-data collection
2. Process-based modelling

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Validated MCR model used
as base to run
Update grid, bathymetry
and boundary conditions
to examine circulation and
sediment transport at
North Head
Higher resolution grid
between North-Head
and the MCR; 15 – 100 m
in longshore direction, 50
m cross-shore
Model Method

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Validated MCR model used
as base to run
Update grid, bathymetry
and boundary conditions
to examine circulation and
sediment transport at
North Head

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Validated MCR model used
as base to run
Update grid, bathymetry
and boundary conditions
to examine circulation and
sediment transport at
North Head

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Morphostatic
simulation;
2-day
morphodynamic
tide
case Hsig [m] Tpeak Dir (deg) %
1 1 10,2 279 0,05
2 2,28 8,6 216 0,02
3 2,29 10 241 0,02
4 2,16 11,4 262 0,04
5 2,16 13 278 0,10
6 2,06 11,4 294 0,10
7 3,88 10,1 224 0,03
8 3,87 12,2 257 0,03
9 3,79 13,9 278 0,04
10 3,71 13,4 291 0,02
11 5,76 12,9 241 0,01
12 5,9 15,1 281 0,01
13 0,7 9,8 271 0,03
case Hsig [m] Tpeak Dir (deg) %
1 1 10,2 279 0,05
2 2,28 8,6 216 0,02
3 2,29 10 241 0,02
4 2,16 11,4 262 0,04
5 2,16 13 278 0,10
6 2,06 11,4 294 0,10
7 3,88 10,1 224 0,03
8 3,87 12,2 257 0,03
9 3,79 13,9 278 0,04
10 3,71 13,4 291 0,02
11 5,76 12,9 241 0,01
12 5,9 15,1 281 0,01
13 0,7 9,8 271 0,03
14 1,67 8,4 221 0,03
15 1,58 9,9 259 0,06
16 1,64 10,4 281 0,14
17 1,53 8,6 300 0,17
18 3,5 10,7 241 0,04
19 3,38 13,2 284 0,05
2-day
morphologic
tide
Schematized
wave-climate

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Morphostatic
simulation;
2-day
morphodynamic
tide
Store the:
hydrodynamics
Sediment
transport vector
fields
and wave heights
• Morphostatic
simulations – no bed
updating.
• Store the results as a
timeseries every 10
minutes.
• These plots show the
mean transports
averaged over 2 tides.

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Morphostatic
simulation;
2-day
morphodynamic
tide
Store the:
hydrodynamics
Sediment
transport vector
fields
and wave heights
Post-Processing:
Scaled with
probability of
occurrence to
derive mean
transports
Input for
Sediment
Transport
analysis &
Sediment
Pathways and
Visualization

15. Mean potential transport during the North Head
pilot (September 20 – December 1, 2018)
• Southern portion of
permit area more active
• Note different scaling
between left and right
maps
Model Results
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16. Model Results; transect-averaged results
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17. Model Results; transect-averaged results
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18. Sediment Pathways Interactive visualization Tool (SPIT)
Background
• We often use streamlines as a Lagrangian way
to visualize steady Eulerian fluid flow fields
Can we get more out of these model results?
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19. Streamlines
• But what happens when the flow field is constantly changing?
• We can represent it with the mean field over a given period and compute
streamlines from that
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20. • We can visualize Lagrangian pathways that
idealized particles would travel as they pass
through the changing vector field
1. Use current velocity field to move
particles passively through the domain
2. Use current velocity field plus add rules
governing the active motion of particles
• Larval swimming behavior
• Entrainment/settling thresholds based on
critical shear stresses
e.g. Delft3D-PART (Deltares, 2015) or PTM
(McDonald et al, 2006), Mdrift
This approach often greatly simplifies the
processes influencing sediment transport
3. SPIT uses sediment transport vector fields
instead of current velocity to advect
particles
4. SPIT is a post-processing routine (matlab)
that uses the existing model output of
Delft3D
Lagrangian representations of
Eulerian flow fields
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21. Lagrangian representations of
Eulerian flow fields
• Release 500 particles in the domain
• Compute the trajectories over a given time
interval e.g. 1 month or 1 year.
• The final end result:
SPAGHETTI?
• Colors indicate wave directions
• Red = from the north-west
• Yellow = from the west
• Green = from the southwest
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22. • We can visualize Lagrangian pathways that
idealized particles would travel as they pass
through the changing vector field
1. SPIT uses sediment transport vector fields
instead of current velocity to advect
particles
2. SPIT is a post-processing routine (matlab)
that uses the existing model output of
Delft3D
3. SPIT results allow us to visualize the
sediment transport pathways
Lagrangian representations of
Eulerian flow fields
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23. Wave height
Sediment trajectories (circles denote
starting locations)
• Constant wave forcing
• Morphologic tide
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24. Particles released within the NH permit area
If the particles move,
most seem to reach
Long Beach, with
some arriving at
Benson Beach
A few even make it to
the navigation
channel
Colored arrows denote wave direction
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25. Benson Beach is
mainly fed by the
Peacock Spit
Particles that pass through Benson Beach polygon
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26. The Navigation
Channel is largely
fed by upstream
sources and the
ebb-tidal delta
Particles that pass through the navigation channel in the MCR
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Conclusions
• Applied to MCR, SPIT allows for evaluation of dredge placement
and its effects on the coast/littoral cell
• Sediment transport pathways form an important element in the
coastal system, but are usually not studied or analyzed
• New analysis technique (SPIT) was developed to better
understand Sediment Transport pathways
• SPIT is NOT a tracer but a Lagrangian visualization of an Eulerian
vector field
• Tools like SPIT allow us to obtain more information from our
model results
• Tools like SPIT combined with animations and visualizations allow
us to better communicate complex model results