Here are the priority actions at national level deemed necessary to ensure the integrated and sustainable management of coastal areas in the short, medium and long term:
• Establish a regime agreement with wide parliamentarian support for the development of inter-institutional partnerships for fully integrated coastal zone management
• Ensure the monitoring of the coastal zone dynamics and the comprehensive sharing of the monitoring data
• Prepare and prove the value of coastal vulnerability and risk maps
• Identify and plan the relocation processes
• Develop an integrated sediment management policy
• Identify the sources of sediment, the dumping sites and the timing of the beach nourishment actions, including the implementation of systems or processes for the transposition of sedi-ments at the river entrances with extended training walls in the West coast.
• Begin the beach nourishment interventions with sedimentary volumes of great magnitude (“shots”); these interventions should be seen as emergency actions in higher risk sections
• Maintain and reconfigure the already established coastal protection schemes in the higher risk sections until it is possible to restore the sediment balance through the beach nourish-ment interventions, including the early “shots”
• Ensure a more effective environmental policing of the coastal zone in order to comply with the coastal land planning legislation.
Since five Coastal Zone Programs (POC) have begun to replace the POOC, it is necessary that the more urgent present recommendations are carefully considered and put into effect without delay in the POC. The method of articulating the priorities proposed here with the POC is, of course, a government prerogative.
Note: The editors are very grateful to Tim O’Riordan for his invaluable help on reviewing an early version of this English version of the Executive Summary.
EXECUTIVE SUMMARY
structures System Exit Fundamental elements of sedimentary dinamycs
1
1a Minho River –
Douro River – ✓✓ – – – – – – – – ✓✓ • rivers are the main sediment source
• potential longshore transport superior to the real sediment transport 1b Douro River – Cabo
Mondego ✓✓ ✓✓✓ – – – – – – – – ✓✓✓ • Douro river constitutes the main sediment source
• real longshore transport equal to the potential transport
1c Cabo Mondego
– Nazaré ✓✓✓ – – – – ✓✓✓ – – – – –
• north longshore transport constitutes the main sediment source
• real longshore transport equal to potential transport
• longshore transport fully captured by the Nazaré canyon
2 Nazaré – Peniche – ✓ – – ✓ – – ✓ – – – • sedimentary sources of reduced magnitude
• residual longshore transport, with high magnitude components
3 Peniche – Cabo Raso – ✓ – – ✓ – – – – – – • rivers constitutes the main sediment source
• Guincho’s dune constitute the main sedimentary sink
4
• Tagus exterior estuary consists of a system in aggradation (accumulation)
4c Rainha’s beach –
Cabo Espichel – – – – – – – – – – ✓✓
• erosion of the cliffs is the main sediment source
• longshore transport equal to real potential transport north of the parallel of Albufeira lagoon
5 Cabo Espichel
– Sines – – ✓✓ – – – – – – ✓✓ –
• erosion of the cliffs is the main sediment source
• Sado’s exterior estuary consists of a system in aggradation (accumulation)
• erosion of the cliffs is the main sediment source
• real longshore transport equal to potential transport east of Garrão meridian
Magnitude of the process Change in sedimentary balance
✓ in the range of 104 m3year-1 change leading to a decrease in coastal risk
✓✓ in the range of 105 m3year-1 change leading to an increase in coastal risk
✓✓✓ in the range of 106 m3year-1 with no significant change in sedimentary balance – null or not significant change compared
to the magnitude of sediment transport in the cell
Subtitle (Tables 1 and 2)
Table 1 - Sedimentary balance at reference.
EXECUTIVE SUMMARY 55
structures System Exit Fundamental elements of sedimentary dinamycs
1
1a Minho River –
Douro River – ✓✓ – – – – – – – – ✓✓ • rivers are the main sediment source
• potential longshore transport superior to the real sediment transport 1b Douro River – Cabo
Mondego ✓✓ ✓✓✓ – – – – – – – – ✓✓✓ • Douro river constitutes the main sediment source
• real longshore transport equal to the potential transport
1c Cabo Mondego
– Nazaré ✓✓✓ – – – – ✓✓✓ – – – – –
• north longshore transport constitutes the main sediment source
• real longshore transport equal to potential transport
• longshore transport fully captured by the Nazaré canyon
2 Nazaré – Peniche – ✓ – – ✓ – – ✓ – – – • sedimentary sources of reduced magnitude
• residual longshore transport, with high magnitude components
3 Peniche – Cabo Raso – ✓ – – ✓ – – – – – – • rivers constitutes the main sediment source
• Guincho’s dune constitute the main sedimentary sink
4
• Tagus exterior estuary consists of a system in aggradation (accumulation)
4c Rainha’s beach –
Cabo Espichel – – – – – – – – – – ✓✓
• erosion of the cliffs is the main sediment source
• longshore transport equal to real potential transport north of the parallel of Albufeira lagoon
5 Cabo Espichel
– Sines – – ✓✓ – – – – – – ✓✓ –
• erosion of the cliffs is the main sediment source
• Sado’s exterior estuary consists of a system in aggradation (accumulation)
• erosion of the cliffs is the main sediment source
• real longshore transport equal to potential transport east of Garrão meridian
(*) without replacement of the coastline
EXECUTIVE SUMMARY
• dredging and extracting in ports often higher than coastal longshore transport
• coastal erosion is the main sedi-ment source
• ensure the nourishment of the beach with all the sand and gravel, class 1 and 2, dredged
1b Douro River –
Cabo Mondego ✓✓ ✓ ✓✓✓ – – – ✓✓✓ – ✓✓✓ – ✓✓✓
• reduction of Douro’s river sediment contribution (extractions and dams)
• sediment retention associated with the port of Aveiro
• coastal erosion is the main sedi-ment source
• artificially feed Espinho’s section - Furadouro
• evaluate the sedimentary reserves on the north mainland shelf
• quantify the solid flow of the Douro under current conditions
• make the sedimentary transposition of Aveiro’s bar
1c Cabo Mondego
– Nazaré ✓✓✓ – ✓✓✓ – – ✓✓✓ ✓✓ – ✓✓ – – • sediment retention associated with
the port of Figueira da Foz
• make the sediment transposition at the mouth of the river Mondego in Figueira da Foz using a bypass
• study the recovery of sediment in the end of the cycle in Nazaré
2 Nazaré – Peniche – ✓ – – ✓ – – ✓ – – – • no significant changes against the
bank in the second half of the twen-tieth century
• artificially feeding the cell with sand out of the system (mainland shelf)
4c Rainha’s beach –
• ensure the nourishment of the beach with all the sand and gravel, class 1 and 2, dredged replace-ment on the beach of all the dredged sediments
• ensure the continuity of feeding at Vale de Lobo section - Garrão Table 2 - Sedimentary balance at current situation.
EXECUTIVE SUMMARY 57
• dredging and extracting in ports often higher than coastal longshore transport
• coastal erosion is the main sedi-ment source
• ensure the nourishment of the beach with all the sand and gravel, class 1 and 2, dredged
1b Douro River –
Cabo Mondego ✓✓ ✓ ✓✓✓ – – – ✓✓✓ – ✓✓✓ – ✓✓✓
• reduction of Douro’s river sediment contribution (extractions and dams)
• sediment retention associated with the port of Aveiro
• coastal erosion is the main sedi-ment source
• artificially feed Espinho’s section - Furadouro
• evaluate the sedimentary reserves on the north mainland shelf
• quantify the solid flow of the Douro under current conditions
• make the sedimentary transposition of Aveiro’s bar
1c Cabo Mondego
– Nazaré ✓✓✓ – ✓✓✓ – – ✓✓✓ ✓✓ – ✓✓ – – • sediment retention associated with
the port of Figueira da Foz
• make the sediment transposition at the mouth of the river Mondego in Figueira da Foz using a bypass
• study the recovery of sediment in the end of the cycle in Nazaré
2 Nazaré – Peniche – ✓ – – ✓ – – ✓ – – – • no significant changes against the
bank in the second half of the twen-tieth century
• artificially feeding the cell with sand out of the system (mainland shelf)
4c Rainha’s beach –
• ensure the nourishment of the beach with all the sand and gravel, class 1 and 2, dredged replace-ment on the beach of all the dredged sediments
• ensure the continuity of feeding at Vale de Lobo section - Garrão
(*) without replacement of the coastline
INTRODUÇÃO
INTRODUÇÃO 61
1. Introdução
1.1. Objetivos
No âmbito do despacho n.º 6574/2014, de 20 de maio, foi constituído o Grupo de Trabalho para o Litoral com o objetivo de “desenvolver uma reflexão aprofundada sobre as zonas costeiras, que conduza à definição de um conjunto de medidas que permitam, no médio prazo, alterar a exposição ao risco, incluindo nessa reflexão o desenvolvimento sustentável em cenários de alterações climáticas”.
Neste contexto, o presente relatório apresenta uma síntese do conhecimento sobre a dinâmica da faixa costeira de Portugal continental em situação de referência e em cenários de alteração climática.
A valorização da zona costeira só poderá ser alcançada através de uma gestão do território assente nos princípios da Gestão Integrada da Zona Costeira (GIZC). Este processo deverá, de uma forma dinâmica, contínua e interativa, harmonizar os valores ambientais, socio-económicos e éticos. Neste sentido, qualquer atuação nesta área deverá procurar um equilíbrio entre valori-zação do território e a preservação dos valores ambientais.
1.2. Conceitos
A zona costeira pode ser genericamente definida como a região onde os processos marinhos e terrestres interagem. Esta definição é compatível com uma região que apresenta naturalmente limites difusos, com elevada variabilidade espacial e temporal. A natureza intrinsecamente ambígua deste conceito faz com que a sua delimitação seja muito variável e dependente do con-texto em que é utilizada (Iddri, 2010). Neste trabalho serão adotadas as definições propostas na Estratégia Nacional para a Gestão Integrada da Zona Costeira (ENGIZC - aprovada pela Resolução do Conselho de Ministros n.º 82/2009, de 8 de setembro):
Zona costeira - Zona costeira é a porção de território influenciada direta e indiretamente, em termos biofísicos, pelo mar (ondas, marés, ventos, biota ou salinidade) e que, sem prejuízo das
INTRODUÇÃO 62
adaptações aos territórios específicos, tem, para o lado de terra, a largura de 2 quilómetros medida a partir da linha da máxima preia-mar de águas vivas equinociais e se estende, para o lado do mar, até ao limite das águas territoriais, incluindo o leito.
Litoral - termo geral que descreve as porções de território que são influenciadas direta e indireta-mente pela proximidade do mar;
Orla costeira - porção do território onde o mar, coadjuvado pela ação eólica, exerce diretamente a sua ação e que se estende, a partir da margem até 500 m, para o lado de terra e, para o lado do mar, até à batimétrica dos 30 m;
Linha de costa - fronteira entre a terra e o mar, assumindo-se como referencial a linha da máxima preia-mar de águas vivas equinociais (LMPMAVE).
zona costeira orla costeira LITORAL
20 0 m ilh as n áu ti ca s ma r te rr ito ri al 30 m ce nt en as de m et ro s 2 k m ce nt en as d e qu iló m et ro s
Figura 1.1 - Conceito de zona costeira e limites conexos (ENGIZC).