E i t l ff t f Shi k i thEnvironmental effects of Ship wakes in the Malamocco‐Marghera Channel

Luca ZaggiaLuca Zaggial.zaggia@ismar.cnr.it

ISMAR has investigated the effects of boat traffic from the ‘90 s 

Several studies performed in the early stages on behalf of the Municipality

these include :

cruise ship wakes in the Bacino S. Marco (Costa and Zuliani 2004, Comune, Proj. Rep.)andsmal boat wakes in several locations, also considering effects on structures (Vazzoler etsmal boat wakes in several locations, also considering effects on structures (Vazzoler etal. 199X)

M t i ti ti i M l M h Ch lMore recent investigations in Malamocco‐Marghera Channel:

February and July 2009 (Future Ocean Excellence cluster funds, Germany)March‐ April 2014 (ISMAR and Ritmare funds)

ISMAR has investigated the effects of boat traffic from the ‘90 s 

Several studies performed in the early stages on behalf of the Municipality

these include :

cruise ship wakes in the Bacino S. Marco (Costa and Zuliani 2004, Comune, Proj. Rep.)andsmal boat wakes in several locations, also considering effects on structures (Vazzoler etsmal boat wakes in several locations, also considering effects on structures (Vazzoler etal. 199X)

M t i ti ti i M l M h Ch lMore recent investigations in Malamocco‐Marghera Channel:

February and July 2009 (Future Ocean Excellence cluster funds, Germany)March‐ April 2014 (ISMAR and Ritmare funds)

A good starting point:Extensive shoreline erosion in Malamocco‐Marghera channel

The past/present situationp p

The past/present situationp p

Erosion is not just on the emerged areas of the j gwestern channel margin, but also affects the submerged shelf on both sides of navigationchannel

In the present situation there is already a largedeficit of SIC and ZPS areas

Shoreline retreat investigated by GIS

Shoreline retreat investigated by GIS

Shoreline retreat 3‐4 m yr‐1

Shoreline retreat investigated by GIS

Shoreline retreat 3‐4 m yr‐1

Shoreline retreat measured in  the field

Shoreline retreat Apr. 2014 – Jan 2015:1.50 – 3.50 m 

Shoreline erosion doesen’t reduce withdistance from channel (present ratedistance from channel (present rate comparable to historic trend)

Erosion rate seems to be higher in gperiods of “acqua alta” (higher tides)

WS 11 ‐ Jul 2014 WS 11 ‐ Sep 2014 WS 11 ‐ Nov 2014 WS 11 ‐ Jan 2015

How much energy is introduced in the system by ship wakes?

https://www youtu

High tide

https://www.youtube.com/watch?v=KMO6StyfMAw&feature=youtu.be

g

https://www.youtube.com/watch?v=FIafdduqMKU&feature youtu be

Ca 3000 events each year

Low tide

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Ca. 3000 events each yearbefore Ro‐Ro terminal waslocated in Fusina

2009 First investigation ‐ 1

Characteristics of ships' depression waves and associated sediment resuspension inVenice Lagoon, Italy

Rapaglia et al., Journal of Marine Systems, 85 (2011), 45‐56Rapaglia et al., Journal of Marine Systems, 85 (2011), 45 56

•Description of the process relevant variables•Associated resuspensionAssociated resuspension•Propagation of wakes

2009 First investigation ‐ 1

Characteristics of ships' depression waves and associated sediment resuspension inVenice Lagoon, Italy

Rapaglia et al., Journal of Marine Systems, 85 (2011), 45‐56 Grande SiciliaRapaglia et al., Journal of Marine Systems, 85 (2011), 45 56

•Description of the process relevant variables•Associated resuspensionAssociated resuspension•Propagation of wakes•Threshold for resuspension•Modified Schoelhammer parameterModified Schoelhammer parameter•Safe speed•Effects of consecutive  passages S=Fr3.5 S1.6

F = v gh‐0.5 S=BD/bhF = v gh 0 5 S=BD/bhB,D ship width and draft B,h channel width and depth

2009 First investigation ‐ 2

Sediment Resuspension by Ship Wakes in the Venice LagoonGelinas et al., Journal of Coastal Research, 29 (2013), 8‐17

•Wakes characterized as a progressive N‐wave with a dominant, leading troughW l i i h 2 1•Water velocities more than 2 m s‐1

•suspended sediment concentrations > 380 mg l‐1•Loads successfully predicted from: current speeds settling velocityspeeds, settling velocity• Sediment flux determined as a function of bottom shear stress. 

Wehr Elbe Novorossysk Star

2009 First investigation ‐ 3

Ship‐wake induced sediment remobilization: Effects and proposed management strategies for the Venice LagoonRapaglia et al., Ocean and Coastal Management, 110 (2015), 1‐11

•Resuspension in shallow water areas: a possiblemechanism for the erosion of central lagoonCh l h li•Channel shoaling

•Propagation of contamination•Criteria for traffic management to minimise effectseffects

2014 Second investigation ‐ 1

Ship‐induced solitary Riemann waves of depression in Venice LagoonParnell et al., Physics Letter A, 379 (2015), 555‐559

•Wakes described in shallow water as strongly non‐linear Riemann waves

•Step‐like profile of the rear slope resulting high water velocities, sediment p p p g g ,resuspension and the overall environmental impact will be much (at least several times) larger than those evaluated based on the linear or weakly nonlinear approaches.

Measured vs. simulated

Simulated wave approaching the shore

2014 Second investigation ‐ 1

Ship‐induced solitary Riemann waves of depression in Venice LagoonParnell et al., Physics Letter A, 379 (2015), 555‐559

•Unprecedented depression wakes of 2.5 m in the channel edge produced by moderate size vessels at low Fr (<0.5) and S (<0.14) (MSC Preziosa S can be as high as 0.21)

•Disturbance is symmetric in the channel margins but becomes highly asymmetric asmargins but becomes highly asymmetric as soon as it gets to the channel edge. The asymmetry is important because it meanshigh velocities on the steep trailing slopehigh velocities on the steep trailing slope

Measured wakes

2014 Second investigation ‐ 2

Numerical simulation of the propagation of ship‐induced Riemann waves of depression into the Venice Lagoon Rodin et al., Proc. Estonian Academy of Science, 64 (2015), 22‐35

•Simulations of the propagation of wakes over the shallows•even depressions of relatively modest amplitude may keep their height at a dangerous l l l di ( 0 3 hi h @ 1 k ) d i h b lik h !level over long distances (up to 0.3 m high @ > 1 km) and with a bore‐like shape!

•Implications on shear stress and resuspension and erosion of central lagoon, but more important: it is not just the biggest ship that cause the problem, almost every ship can move sediments creating erosion.

Space–time (x–t) diagram of the simulated wave profile produced by thep ( ) g f p f p ydepression wave with the initial amplitude A0 = 1 m propagating to the eastern(lagoon) side of the channel.

2014 Second investigation – 3, 4 and 5

Ship wakes and fast shoreline retreat in the central lagoon of Venice Zaggia et al., in prep.  (2016) ‐ (see introductory slides)

Environmental effects of ship wakes in coastal areas, is global traffic sustainable?Environmental effects of ship wakes in coastal areas, is global traffic sustainable?AA.VV. in prep. (2016)

•Venice is not unique (Galveston‐Houston mistery; GIWW‐USACE; Fort Lauerdale, Florida; large European Rivers)•Further investigation on  the behaviour of dense fluid‐mud suspensions to properlydescribe and predict morphological problems like local and large scale erosion and h l i fillichannel infilling.

•Safety issueswith 30 cm wave height with strongly steep rear slope•Resuspension and release of contaminants?

https://www.youtube.com/watch?v=q2OQOAFq‐hY

https://www.youtube.com/watch?v=5h‐Reroj3XM

https://www.youtube.com/watch?v=kyY0fzqEIRE

ElbeF. Lauerdale N. Zealand

Elbe River in Hamburg