International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 6
Number 4
December 2012
1 INTRODUCTION
The Juqueriquerê Catchment is the major in São
Paulo State (Brazil) North Coastline (Fig. 1). The
Juqueriquerê Waterway is a 4 km estuarine channel
used by small piers and docks. The entrance bar
doesn’t have any amelioration works and the boats
maneuvers are difficult and dangerous. Beyond
environmental impacts, the cost - effective
improvements consists to bar jetties calibration, this
solution means to talk about costs of 5 M €, or the
permanent maintenance with local dredging works,
which costs, in the long term of decades, will be the
same.
According to the IPCC forecasting, there is the
awareness that conditions of bathymetry, tides,
winds, currents and waves for next decades shall
have climate changes impacts. The project goal is to
overcome the contraposition that it emerges between
the defence against the hydraulic risk and the
management to preserve the environmental
protection for nautical purposes. The risk is
understood, in a qualitative way, as composed by
Hazard, Exposure and Vulnerability (Kron 2008).
2 SOME HISTORY
Example of navigation possibilities in the waterway
was the dock operation of the English Lancashire
General Investments Company, owner of the Blue
Star Line Navigation Company. In the period 1927 -
1967, the “Fazenda dos Ingleses” (English Farm),
has sent the tropical fruits production to England.
The railway line of the farm had 120 km, with docks
and warehouses in the right bank of the estuary. The
Packing House, in the dock area, was considered the
Coastal Area Prone to Extreme Flood and
Erosion Events Induced by Climate Changes:
Study Case of Juqueriquere River Bar
Navigation, Caraguatatuba (Sao Paulo State),
Brazil
E. Arasaki
Escola Politécnica da USP, Sao Paulo, Brazil;Instituto Nacional de Pesquisas Espaciais,
S.J.Campos, Brazil
P. Alfredini
Escola Politécnica da USP, Sao Paulo, Brazil; Instituto Mauá de Tecnologia, Sao Caetano do
Sul, Brazil
A. Pezzoli & M. Rosso
Politecnico di Torino, Turin, Italy
ABSTRACT: According to the IPCC, the forecast for the year 2100 is an increasing of global average
temperature, whose impacts in winds, waves, tides, currents and bathymetry will produce real risks of
extreme events due to climate changes. Juqueriquere River is Sao Paulo State (Brazil) North Coastline major
waterway. Due to minimum channel depths in the coastal bar, navigation is only possible for small leisure
crafts and fishing boats and some cargo barges during higher tidal levels. This study case has been evaluated
according to the relative sea level and wave climate scenarios forecasting, based on the meteorological
recognition patterns of the last decades data for tides and waves. The impact of climate changes is obtained
from this knowledge. The main goal of this paper is to have the initial conceptual description about the
impacts on the bar navigation conditions of Juqueriquere to obtain guidelines for master nautical plans.
571
second of this type in South America. The cargo
boats, more than 20 in the forties decade, had an
individual load of 55 dwt (Fig. 2). In March 1967, a
strong debris-flow, rain more than 600 mm in 2 days
(monsoonal rates), combined with storm surge,
caused more than 400 casualties and material losses
in Caraguatatuba. After that, the docks were closed
(Arasaki 2010).
In the last four decades, the nautical purposes of
leisure and fishing boats increased. It is important to
mention the recent interest as supplier area for the
offshore LNG and oil. The plant for the gas
treatment is located in the left bank of the river and
many of the facility heavy cargo equipments used
large barges push-pulled by tugs (Fig. 3).
3 TIDE VARIABILITY
Considering the CDS (Companhia Docas de Santos)
datum, extreme LLW level, in Figure 4 are
presented our study conclusions about São Paulo
State coastline tidal variability for the last six
decades (1944 - 2007). A consistent linear response
shows: 1. Overall period: rising rates (cm/century)
for MSL (23.2), HHW (36.5) and LLW (41.8); 2.
Period before 1969: 1.1, - 7.3 and 54.3 and 3. Period
after 1975: 40.9, 44.9 and 75.4.
Figure 1. Location map with significant height and average period local wave roses.
572
Figure 2. Boats moored at the quay, dockyards warehouses and railway terminal (1940 decade) of the English Farm.
Figure 3.Heavy cargo equipments using large barges push-pulled by tugs (February 2010).
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Figure 4. Annual tidal levels variability (1944 – 2007) for São Paulo State (Brazil) coastline.
4 FLUVIAL MORPHOLOGY
The Juqueriquerê Catchment has the following main
features: area of 430 km
2
, long term average
discharge of 11 m
3
/s, heavy rainfall rates (around
3000 mm/year) producing high fluvial sediment
transport, floods and debris-flows. The last ones are
due to the steep slopes and the altitude (~ 1000 m) of
the Serra do Mar mountains near the coast,
producing the orographic effect, which rapidly
condensates the sea humidity.
The fluvial dynamics is of high solid transport
capacity and fluvial and coastal morphology
transformations, combined with recurrent and
intense flood events that cause extensive risks and
damages to population and infrastructures, causing
riparian and coastal region with important anthropic
impact.
Strong debris-flows occur in this region, because
events similar to monsoonal rain rates (higher than
300-400 mm per day) occur in multi decadal
periods. The region history records shows this type
of strong events in 1859, 1919, 1944 and the last and
more catastrophic in March 1967, Figure 5 shows
the damage caused in the English Farm dock yard,
warehouses and Packing House (Arasaki, 2010).
5 WAVE CLIMATE
According to Marquez & Alfredini (2010), the
offshore climate may be described by the ECMWF –
European Centre for Medium-Range Weather
Forecast – ERAS40 project. In Figure 6 are
presented the H
s
, significant wave height, and T
z
,
average period, for the nearest grid point 1958 -
2001 data series. The local wave climate may be
described by the H
s
and T
z
roses in Figure 1,
obtained from the coastal buoy data records survey
of São Paulo State coastline (1982 - 1984) treated
with the DHI software MIKE 21 NSW (Nearshore
Waves).
6 COASTAL SEDIMENTS AND
MORPHOLOGY
In general, sediment’s samples near the bar show
dominance of material like fine sand, silt and clay.
According to Venturini (2007), the grain size
proportion of clay and silt in the first 2.0 m from the
bottom surface were 15 to 20% and 35 to 55%,
respectively.
The waterway is strongly restricted by the
maritime bar depth, 0.3 - 0.5 m according to Chart
Datum (MLWS) with MSL (Z
0
) of 0.7 m, and the
entrance is instable, with seasonal migration. Indeed,
according to Bruun (1978) criteria for overall
stability, the preliminary evaluation of Ω/M
tot
, ratio
of the spring tidal prism per total littoral drift, is 5 to
10. The Ω is of the order of 1.0 Mm
3
, including river
discharge, and M
tot
, based on local breaking wave
climate, is around of 0.1 Mm
3
/year. For ratios less
than 20, there are comprehensive bars with very
shallow depth, being typical bar-bypassers, and in
this case depending upon the strong flushing during
the rainy season.
The morphological behavior of the bar is being
studied based on seasonal thalweg bathymetrical
surveys (Fig. 7) correlated with meteorological
conditions corresponding to the three months before
accumulated rain: April 2004: 382 mm; March 2009:
688 mm; September 2009: 313 mm; February 2010:
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634 mm and September 2010: 463 mm. Wave
climate is also considered.
7 CONCLUSIONS
Considering the awareness about the importance of
climate changes impacts in a coastal area prone to
extreme flood and erosion events, important issues
to support confidence, or not, to the decision of
construct two jetties (rigid structures) solution,
maintenance dredging (flexible solution), or non
intervention in the waterway are:
− 1. There is an overall sea level rising trend, which
matches with the IPCC forecasting; 2. LLW has
the highest rate of linear tidal rising (75
cm/century); 3. There is an overall tidal range re-
duction; 4. The tidal prism will change, and the
tidal currents velocity should increase, if the
HHW levels will drown large fluvial areas, com-
pensating the velocity reduction due to the tidal
range decreasing; 5. Considering the issues
above, the river bar depth should increase and 6.
The overall rise of the sea will produce more
coastal erosion and littoral drift, in opposition to
the outcome of issue 5.
− It is possible to observe a general significant
height and average period wave increasing for
annual averaged figures over than 1.5 m and 8.0
s, and the corresponding decadal maximum wave,
from 3.9 m and 13.0 s in the sixties to 4.5 m and
14.5 s in the nineties. It means increasing swell.
Hence, should be a trend to increase littoral drift,
reducing bar depth.
− There are some areas of mud, which may be fluid
sufficient to consider the nautical bottom concept
(PIANC et al. 1997), in practice for mud density
lower than 1250 kg/m
3
. In these cases it is possi-
ble to reduce the under keel clearance. The analy-
sis of September 2010 and March 2011 survey,
with detailed samples of the bar and bathymetry,
should provide confidence for this answer.
− About the thalweg shifting migration, it is possi-
ble to conclude: 1. Like for the monsoon weather,
the main channel alignment depends upon flood
periods, according to rain rate of; 2. The shifting
between two adjacent thalwegs may be produced
by extreme river flow conditions, or a storm
surge.
Awareness with climate changes impacts
importance for the intervention’s plan must be
considered to obtain a final balanced solution among
structures, dredging and non structural measures for
nautical master plan.
It is important to recognize that great natural
events are not avoidable, but great disasters are, as
the ancient Greek Aristotle (384-322 B.C.) said, “It
is probable that the improbable will happen” (Kron
2008). Unfortunately, closing this paper, we have to
recognize this historical truth: in January 2011, a
very large debris-flow phenomena (more than 600
mm rain rate in two days) in the Serra do Mar
mountains of Rio de Janeiro State (Brazil), which
border São Paulo State, killed more than 700 people,
being considered by the ONU the eighth of this type
since 1900.
We want to provide an intervention’s plan for
Juqueriquerê Waterway for the next 50 years about
geomorphologic, structural and no-structural
hydraulic shape in reference to: 1. Plani-altimetric
historical evolution analysis of the coastal thalweg,
validating migration model considering wave
climate, tides and fluvial discharges; 2.
Morphological analysis of bankfull, floodplains and
perifluvial areas; 3. Grain size analysis of
transported sediments; 4. Meteorological and
oceanographic analysis (Pezzoli et al. 2004a and
2004b; Cristofori et al. 2004) 5. Hydraulic analysis
by using software HEC_RAS of US Army Corps of
Engineers. After, we want to draft a maintenance
plan for Juqueriquerê Waterway reckoning on the
basis: 1. Ordinary maintenance isn’t replaceable
with structures; 2. Maintenance actions must be
specific, pointed and planned; 3. Maintenance works
must be well-according with landscape and with the
ecosystem.
Figure 5. Destruction in the dock area and Packing House of
English Farm after the debris flow of March 1967.
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Figure 6. Deep water wave data series of H
s
and Tz (1958 – 2001).
Figure 7. Entrance channel thalweg in rainy (April 2004, March 2009, February 2010) and dry (September 2009 and 2010)
seasons.
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8 ACKNOWLEDGEMENTS
This paper has the financial support of CAPES,
Human Resources Improvement Agency of
Brazilian Government. The authors also want to
thank the support of São Paulo University,
Politecnico di Torino, Instituto Nacional de
Pesquisas Espaciais, Instituto Técnico da
Aeronáutica, Instituto Mauá de Tecnologia.
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