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THE STABILIZATION OF THE FARO-OLHÃO INLET AND ITS INFLUENCE ON THE MORPHODYNAMICS OF THE STABILIZATION OF THE FARO-OLHÃO INLET AND ITS INFLUENCE ON THE MORPHODYNAMICS OF

THE STABILIZATION OF THE FARO-OLHÃO INLET AND ITS INFLUENCE ON THE MORPHODYNAMICS OF - PowerPoint Presentation

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THE STABILIZATION OF THE FARO-OLHÃO INLET AND ITS INFLUENCE ON THE MORPHODYNAMICS OF - PPT Presentation

SantosFerreira E Dias A TrigoTeixeira C Santos J Leal N Oliveira and J Peleja Instituto Portuário e dos Transportes Marítimos IP Instituto Superior Técnico ID: 801399

armona inlet faro evolution inlet armona evolution faro olh

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Slide1

THE STABILIZATION OF THE FARO-OLHÃO INLET AND ITS INFLUENCE ON THE MORPHODYNAMICS OF CULATRA ISLAND AND ARMONA INLET

Santos-Ferreira* , E. Dias* , A. Trigo-Teixeira** , C. Santos*** , J. Leal* ,

N. Oliveira*

and

J. Peleja*

* Instituto Portuário e dos Transportes Marítimos, I.P.

** Instituto Superior Técnico

*** Faculdade de Ciências e Tecnologia da

Univ

. NOVA

Slide2

SumaryINTRODUCTIONGEOLOGY AND GEOMORPHOLOGY

METHODS

EVOLUTION OF ARMONA INLET AND CULATRA ISLAND

FARO-OLHÃO INLET OPENING AND EVOLUTIONDISCUSSION AND CONCLUSIONS

2

Slide3

IntroductionStudy area is located in the Faro lagoon - Ria

Formosa;

Large structural and

morphodynamic diversity and it is the most important wetland area in southern PortugalGeological environment: marshes that cover about two thirds of the area. The system consists of a series of barrier islands at the southern most part.

3

Slide4

IntroductionThey act as a protection from the sea and are separated by migrating inlets, some are fixed artificially, establishing the communication between the lagoon and the ocean.The islands and peninsulas are separated by six tidal inlets which allow water, sediment, chemicals and nutrients to be exchanged between the lagoon and the ocean.

Two bars (Faro-

Olhão

and Tavira) are artificial, stabilized with jetties.4

Slide5

IntroductionThe evolution of the Ria

Formosa lagoon is largely determined by

morphodynamics

found in coastal lagoons:considering the phenomena of erosion and sedimentation, littoral transport.It is presented a study of the morphodynamics

of

Culatra

island and consequent evolution of

Armona

inlet since the XIX century, defining the average progression and development in different periods.

It is presented an evaluation of the influence of the opening of Faro-

Olhão

inlet (1929) on the evolution of

Culatra

island and Armona inlet.

5

Slide6

Geology and Geomorphology

Most of the formations had their origin in the Quaternary geological period.

The geological history show a complex evolution, including marine transgression and regression phases, erosion, coastal sediment transport, and seismic activity.

Marshes are the dominant geological environment > are alluvial formations of black clay, whose progression to the sea is blocked by sedimentation and by the islands. It is worth mentioning the presence of large masses of sand that make the barrier islands of the coast.

6

Slide7

Geology and Geomorphology

Presently, the system of barrier islands of Faro lagoon consists of:

two peninsulas (

Ancão and Cacela) which are respectively the western and eastern limits of the system; five barrier islands (from west to east:

Barreta

,

Culatra

,

Armona

,

Tavira

and Cabanas);

a vast body of water, the lagoon.

7

Slide8

Geology and Geomorphology

The islands and peninsulas are separated by six tidal inlets (

Ancão

, Faro-Olhão, Armona, Fuzeta

,

Tavira

,

Cacela

), which allow the exchange of water, sediment, chemicals and nutrients between the lagoon and the ocean.

The area of the lagoon is

12 000ha

and the area of the peninsulas and the barrier islands is about

2 000ha.

The Western side of the system is more energetic, directly exposed to the dominant wave action from W and SW (68%);

The Eastern

side is exposed to the "

Levante

" - SE winds from the Mediterranean, (25%).

8

Slide9

MethodsTo carry on an analysis of the evolution of Culatra

island and Nova and

Armona

inlets:Compilation of all available information from the XIX century till the present;Digitalization of the information, and subsequent integration into a GIS, where the coordinate system of all the information was defined; Perform the operations of spatial analysis leading to the study of coastal evolution. Development of digital terrain models (DTM) for each survey available;

9

Slide10

MethodsAn hydrodynamic study of the lagoon complex was used to correlate the information, and to allow the interpretation of the system behavior.Recent experimental data, from 1999 and 2000, referring the velocity, flow and tide, in the several inlets of the lagoon, was also used.

The influence of the Faro-

Olhão

jetties in the littoral drift, and in the evolution of the Culatra island, is also discussed.10

Slide11

Evolution of Armona Inlet and Culatra Island

Armona

inlet is the most important for the water exchange between the lagoon and the sea.

Since 1873 the width has been narrowing, slowly first, but since 1955 much more rapidly. It is established the natural rate of closure of this inlet, as well as assess the influence of the opening and stabilization of the Faro-Olhão inlet. It is presented the evolution in some periods, using the existing topography, and using also some GIS tools.

11

Slide12

Evolution of Armona Inlet and Culatra Island

12

1873

Slide13

Evolution of Armona Inlet and Culatra Island

From 1873 to 1929

In this period the Faro-

Olhão inlet was closing at rate of 14m per year, in average.1929 > opening of the Faro-

Olhão

inlet > first phase

1873 >

t

he total width of the

Armona

inlet was 4050m.

1930 > the total width of the

Armona

inlet was 3300m.13

Slide14

Evolution of Armona Inlet and Culatra Island

Armona

inlet DTM in 1873, 1916 and 1930.

14

Slide15

Evolution of Armona Inlet and Culatra Island

Difference between 1873 to 1916

hydrography

;Difference between 1916 and 1930 hydrography.

The brownish colors represent sedimentation, the blue ones erosion.

15

Slide16

Evolution of Armona Inlet and Culatra Island

From

1930 to 1950

First phase of Faro-Olhão construction: 1929 – 1930Final construction of the jetties: 1950 -1955;1930-1950: period of a slowing down of the closing of the Armona

inlet, with an average rate of 8m per year. So this inlet presented in 1950 an opening of 3150m.

16

Slide17

Evolution of Armona Inlet and Culatra Island

From

1950 to

the presentFrom 1955 till 2002 Armona inlet closed with an increased rate of 48m per year;

In 1980 > still identify the Nova and

Armona

channels;

In 2002 the Nova channel has disappeared and only one channel was present in the inlet;

In 2007 the width of

Armona

inlet was only 540m.

17

Slide18

Evolution of Armona Inlet and Culatra Island

DTM 1980

and 2002.

18

Slide19

Evolution of Armona Inlet and Culatra Island

Difference between 1930 to 1980

hydrography

;Difference between 1980 to 2002 hydrography; The reduction of the inlet width is accompanied by the channel deepening.

19

Slide20

Evolution of Armona Inlet and Culatra Island

3D Model of the

Armona

inlet (2002) spring ebb tide and spring flood tide.20

Slide21

Evolution of Armona Inlet and Culatra Island

Evolution of the

Armona

and Nova channels, from 1873 to 2007. 21

Slide22

Evolution of Armona Inlet and Culatra Island

Evolution of

Culatra

and Armona islands, from 1873 to 2007.22

Slide23

Evolution of Armona Inlet and Culatra Island

Evolution of the

Armona

inlet, from 1873 to 2007.23

Slide24

Faro-Olhão Inlet Opening And EvolutionDTM of the Faro-

Olhão

inlet, for the years 1955, 1967, 1976, 1985 and 2008.

24

Slide25

Faro-Olhão Inlet Opening And EvolutionFaro-

Olhão

inlet from 1929 to 1950

No significant changes in this inlet since its opening in 1929 till the conclusion of the jetties, in 1955.25

Slide26

Faro-Olhão Inlet Opening And EvolutionFaro-

Olhão

inlet from 1955 to 2008

The Faro-Olhão inlet, as its stabilization works were designed, and an aerial photograph as it was in 2007. 26

Slide27

Faro-Olhão Inlet Opening And EvolutionSedimentation and erosion for the Faro-

Olhão

inlet, for the periods 1955-1985, and 1985-2008.

27

Slide28

Faro-Olhão Inlet Opening And EvolutionDiscussion of the Faro-

Olhão

inlet evolution

Evolution of the Faro-Olhão inlet, from 1958 to 2010.28

Slide29

Faro-Olhão Inlet Opening And EvolutionThe velocity pattern in Faro lagoon.

29

Slide30

Discussion and Conclusions

It is clear the importance that the opening of the Faro-

Olhão inlet had both in littoral drift and in the evolution of the old Nova channel and consequently in the evolution of the inlet of Armona, after the junction of the two channels.

30

Slide31

Discussion and Conclusions

It seems that there is a tendency in

Armona island to increase to the west, and not to erode that edge, so that the existing human settlement in this island is not expected to be at risk in the near future. The tendency of Faro-Olhão inlet to reach a balance in the long term may be at risk if the

Armona

inlet closes.

In this case, the closing of this inlet will probably force the opening of a new inlet somewhere near of the Faro-

Olhão

inlet.

31

Slide32

Discussion and Conclusions

A further study using a finite element circulation model is planned, using the data from Ventura Soares (2001), with 2000 topography for calibration, but using 2011 topography for the study.

It seems important to try to understand the flow pattern in the Faro-Olhão inlet, and the reason of the deepening so far away from the mouth defined by the breakwaters.

32

Slide33

Thank You33