E itl ff t fShi ki th EnvironmentaleffectsofShipwakesin the Malamocco

EEnvironmental
i
t l effects
ff t off Ship
Shi wakes
k in the i th
Malamocco‐Marghera Channel
Luca Zaggia
Luca
Zaggia
l.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.)
and
smal boat wakes
boat wakes in several
in several locations, also
locations, also considering effects on structures
on structures (Vazzoler et
al. 199X)
M
More recent
t investigations
i
ti ti
i M l
in Malamocco‐Marghera
M h
Ch
Channel:
l
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.)
and
smal boat wakes
boat wakes in several
in several locations, also
locations, also considering effects on structures
on structures (Vazzoler et
al. 199X)
M
More recent
t investigations
i
ti ti
i M l
in Malamocco‐Marghera
M h
Ch
Channel:
l
A good starting point:
February and July 2009 (Future Ocean Excellence cluster funds, Germany)
Extensive
shoreline erosion in March‐
April 2014 (ISMAR and Ritmare funds)
Malamocco‐Marghera channel
The past/present
p
p
situation
The past/present
p
p
situation
Erosion is not jjust on the emerged
g areas of the western channel margin, but also affects the submerged shelf on both sides of navigation
channel
In the present situation there is already a large
deficit 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 with
distance from channel (present rate rate
comparable to historic trend)
Erosion rate seems to be higher
g
in periods 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
https://www
youtu
be.com/watch?v=K
MO6StyfMAw&fea
ture=youtu.be
High tide
g
https://www.yout
ube.com/watch?v
=FIafdduqMKU&fe
ature youtu be
ature=youtu.be
Low tide
Ca. 3000 events each year
Ca
before Ro‐Ro terminal was
located in Fusina
2009 First investigation ‐ 1
Characteristics of ships' depression waves and associated sediment resuspension in
Venice Lagoon, Italy
Rapaglia et al., Journal of Marine Systems, 85 (2011), 45
Marine Systems, 85 (2011), 45‐56
56
•Description of the process relevant variables
•Associated
Associated resuspension
•Propagation of wakes
2009 First investigation ‐ 1
Characteristics of ships' depression waves and associated sediment resuspension in
Venice Lagoon, Italy
Rapaglia et al., Journal of Marine Systems, 85 (2011), 45
Marine Systems, 85 (2011), 45‐56
56
•Description of the process relevant variables
•Associated
Associated resuspension
•Propagation of wakes
•Threshold for resuspension
Modified Schoelhammer parameter
•Modified
•Safe speed
•Effects of consecutive passages
Grande Sicilia
S=Fr3.5 S1.6
0 5 S=BD/bh
FF = v gh
= v gh‐0.5
B,D ship width and draft
B,h channel width and depth
2009 First investigation ‐ 2
Sediment Resuspension by Ship Wakes in the Venice Lagoon
Gelinas et al., Journal of Coastal Research, 29 (2013), 8‐17
•Wakes characterized as a progressive N‐wave with a dominant, leading trough
‐1
1
•Water velocities more than 2 m s
W
l ii
h 2
•suspended sediment concentrations > 380 mg l‐1
•Loads successfully predicted from: current speeds settling velocity
speeds, 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 Lagoon
Rapaglia et al., Ocean and Coastal Management, 110 (2015), 1‐11
•Resuspension in shallow water areas: a possible
mechanism for the erosion of central lagoon
•Channel
Ch
l shoaling
h li
•Propagation of contamination
•Criteria for traffic management to minimise effects
2014 Second investigation ‐ 1
Ship‐induced solitary Riemann waves of depression in Venice Lagoon
Parnell et al., Physics Letter A, 379 (2015), 555‐559
•Wakes described in shallow water as strongly non‐linear Riemann waves
•Step‐like
p
profile of the rear slope
p
p resulting high water velocities, sediment 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 Lagoon
Parnell 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 as margins but becomes highly
as
soon as it gets to the channel edge. The asymmetry is important because it means
high velocities on the steep
high 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
level over long distances (up to 0.3 m high @ > 1 km) and with a bore‐like shape!
l
di
(
0 3 hi h @ 1 k ) d i h b
lik h
!
•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
p
((x–t)) diagram
g
off the simulated wave p
profile
f
produced byy the
p
depression 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?
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 properly
describe and predict morphological problems like local and large scale erosion and channel
h
l infilling.
i filli
•Safety issues with 30 cm wave height with strongly steep rear slope
•Resuspension and release of contaminants?
https://www.
youtube.com/
watch?v=q2O
QOAFq‐hY
F. Lauerdale
https://www.y
outube.com/w
atch?v=5h‐
Reroj3XM
Elbe
https://www.y
outube.com/w
atch?v=kyY0fzq
EIRE
N. Zealand
Elbe River in Hamburg