Coastal Evolution

The main objective of this work was to deduce the several phases of the formation and development of the tombolo that converted the ancient island of Peniche into a peninsula. For that historical documents and maps were analyzed and interpreted, crossing this analysis with the morphdynamic data of this Portuguese coastal stretch. In order to contextualize the forcing mechanisms, the direct or indirect
influence of the nearby geographical accidents have also been taken into account, namely the evolution of the Alfeizerão and Óbidos lagoons. Particularly important is the analysis of the medieval port of Atouguia da Baleia evolution, in front of Peniche. The silting up of this coastal reentrance favored and accelerated the tombolo progression. Peniche became a watch area and a fort was constructed when being an Island or a Peninsula depended on the tide. Currently Peniche is definitely a peninsula. Since the Roman Cassius or the crusader Osberne (or Osborne) mentioned Peniche until the contemporary period many centuries have passed and during that this coastal area was in slow transformation. For a long time Peniche was neither island nor peninsula, being in different intermediate phases between the two stages. Hence the unjustified attack Alfredo Fernando Martins made to the map of Fernando Bandeira Ferreira, in the in the middle of the last century, criticizing him for representing Peniche as an island in the 14th century. In fact, we believe that at that time the tombolo should already be in broad development, anchored on the coast, that
was in progressive silting up, maybe already in a state that allowed looking at Peniche like a peninsula at the syzygy low tide, but whose configuration, during the high tide, would certainly be that of an island.

Efectua-se a caracterização dos tipos de litoral entre Espinho e Nazaré, incluindo dados complementares, nomeadamente quanto à litologia, estrutura e evolução recente.
Procede-se à identificação e caracterização da ocupação humana, incluindo a inventariação de obras de protecção costeira existentes e outras formas de artificialização da faixa litoral.
Caracterizam-se alguns aspectos oceânicos, como sejam os movimentos das águas superficiais (marés, ondas, temporais, tsunamis ...) e as variações do nível do mar.
Propõe-se uma estratégia de gestão da faixa costeira considerada, numa perspectiva de desenvolvimento sustentável.
Fazem-se recomendações de actuações a curto, médio e longo prazo.


Characterization of the coastline types between Espinho and Nazaré (Portugal) is carried out, including complementary data, namely regarding lithology, structure and recent evolution.
Human occupation is identified and characterized, including the inventory of existing coastal protection structures and other forms of artificialization of this coastal stretch.
Some oceanic features are characterized, such as surface water movements (tides, waves, storms, tsunami ...) and mean sea level variations.
A strategy for coastal management is proposed, with a view to sustainable development.
Recommendations for short, medium and long term actions are made.

Resumo-Cordões litorâneos regressivos do tipo dunas frontais (foredune ridges) e do tipo praia (beach ridges) são elementos morfológicos muito comuns em margens de lagoas e lagunas costei-ras, embora ainda pouco estudados. Neste trabalho, são apresentados resultados do estudo de uma planície de cordões litorâneos regressivos arenosos que se formou na margem NE da Lagoa dos Quadros, no litoral norte do Rio Grande do Sul. A partir da análise de fotografias aéreas, levanta-mentos altimétricos, perfis de georadar (GPR), testemunhos de sondagem e amostras superficiais, foram investigadas a morfologia da planície de cordões e o arcabouço estratigráfico de seus respec-tivos depósitos sedimentares. A planície é composta por 20 cordões contínuos e semi-contínuos, de baixa amplitude e espaçados de 5 a 50 m. Sobre uma fácies basal de fundo lagunar que se formou aproximadamente entre 7 e 6 ka, desenvolveu-se uma sequência regressiva de modo agradacional e progradacional composta por depósitos de antepraia, de pós-praia/face de praia, dunas frontais e depósitos de leque de sobrelavagem. Dunas transgressivas adentrando na lagoa a partir da barreira holocênica IV (barreira de Curumim) podem ter sido uma importante fonte de areia para o desen-volvimento da planície de cordões. Palavras-chave: GPR, cordão de praia, cordão de duna frontal, sequência regressiva, barreira com-plexa, lagoa costeira. Abstract-Geomorphology and depositional architecture of a strandplain at the ne margin of Quadros Lagoon, RS, Brazil. Foredune ridges and beach ridges are morphological elements largely present in coastal lakes and coastal lagoons. However, it still requires further studies. This paper presents results of a prograding strandplain (sand ridge plain) developed at the NE margin of Quadros Lagoon, in the northern littoral of Rio Grande do Sul. Aerial photographs analysis, topo-graphic surveying, GPR records, soundings and surface samples allowed to study the morphology of the strandplain and the stratigraphic framework of their respective sedimentary deposits. The strandplain comprises 20 continuous and semi-continuous ridges, of low amplitude and spaced 5 to 50 m. A regressive sequence comprising deposits of shoreface, backshore/beachface, foredunes and washover fans was developed aggradacionaly and proggradacionaly over a basal facies of a lagoon bottom, between the last 7 to 6 ky. Transgressive dunefields from the Holocene barrier IV (Curumim barrier) to Quadros Lagoon was probably an important source of sand for the strand-plain development.

This study describes advances in understanding of the recent
evolution of the Ombrone River delta. Several aspects have
been studied and updated: the stages of progradation and retreat of the shoreline from the Middle Ages, with particular reference
to the last 200 years, have been reconstructed and the natural
and/or human forcing responsible for the area’s evolution have
been hypothesized.
The processes that led to the formation and evolution of
some small coastal lakes and the more recent evolution of the
shoreline are defi ned. Monitoring of shoreline variations in the
Ombrone Delta apex has been achieved by comparing aerial
photos acquired in 1995, 1998, 2004, 2006 and 2010. The progressive landward migration of the shoreline has resulted in a
realignment of the coast. Comparison with older erosion and
progradation rates shows decreasing erosion rates along the
delta apex with time: the erosion rate of the northern wing has
reached peaks of around 14 m/yr (2004-2006), and then fallen
to 4.5 m/yr in the latest period (2006-2010).
The Ombrone River delta is characterized by the presence
of beach ridges, ponds and, in the past, of a coastal lake. Morpho-bathymetric analysis and comparison with historical maps shows that during the XIX century, the historical lake preserved
its geometry; only in the 1883 map seaward side presents an
irregular geometry, while in the 1929 map the ponds have been
represented for the fi rst time and are located seaward with respectto the XIX century beach ridge.
Comparing morpho-bathymetric data of Chiaro Grande pond
and submerged apical mouth, this study confi rmed the hypothesis
about Chiaro Grande pond genesis in which its formation is based on the closure of a narrow sea stretch consequent to the
emergence of a bar. The independence between the genesis of
ponds and lake evolution, highlighting the importance of mouth
bar growth as a recurrent mechanism for confi ning narrow sea
stretches.
The orientation of morphological features and the prevailing
wave climate suggest a sediment transport from south to north.

The Araruama lagoon system, located in a coastal lowland region of the State of Rio de Janeiro / Brazil, is historically known by its abundant production of salt. It is a hypersaline lagoon water body, confined after the formation of a double sandbar during the Pleistocene and Holocene. The high salinity levels are explained due to the protection afforded by the sandbar, regarding the direct impact of the ocean, the conditions related to the tropical climate, the low average depth of the lagoon, its insignificant river drainage and the rapid evaporation provided by Northeast winds. In the seventeenth and eighteenth centuries, this marine resource was already explored. However, the salt was monopolised by the crown and its production was not encouraged in order to stimulate the importation of the product from Portugal. After the nineteenth century monopoly regulations ended, new techniques of exploration were introduced, and the production increased, based on the proliferation of salt fields, unleashing a significant transformation of the landscape. This study aims to analyse how was the intensification of human disturbance at the lagoon system, between that legislative event and the year 1900. For that purpose, historical documentation was analysed, such as legislation on salt, the provincial government reports, announcements published in Rio de Janeiro state newspapers and mainly emphyteusis of Cabo Frio municipality properties.

Riassunto-in questo lavoro è stata ricostruita la variazione della linea di riva dell'intero litorale pisano per il periodo 1938-2004 e sono state valutate quantitativamente le corrispondenti variazioni areali di spiaggia. Lo studio si è basato sull'analisi e georeferenziazione di oltre 340 fotogrammi con i quali sono stati ricostruiti 18 fotomosaici dell'intera area di studio, ciascuno corrispondente ad un diverso anno di osservazione. L'analisi di ogni fotomosaico ha consentito di individuare la posizione della linea di riva ...

Background, Aim and Scope Coastal and river plains are the surfaces of depositional systems, to which sediment input is a parameter of key-importance. Their habitation and economic development usually requires protection with dikes, quays, etc., which are effective in retaining floods but have the side effect of retarding sedimentation in their hinterlands. The flood-protected Dutch lowlands (so-called dike-ring areas) have been sediment-starved for up to about a millennium. In addition to this, peat decomposition and soil compaction, brought about by land drainage, have caused significant land subsidence. Sediment deficiency, defined as the combined effect of sediment-starvation and drainage-induced volume losses, has already been substantial in this area, and it is expected to become urgent in view of the forecasted effects of climate change (sea-level rise, intensified precipitation and run-off). We therefore explore this deficiency, compare it with natural (Holocene) and current human sediment inputs, and discuss it in terms of long-term land-use options. Materials and Methods: We use available 3D geological models to define natural sediment inputs to our study area. Recent progress in large-scale modelling of peat oxidation and compaction enables us to address volume loss associated with these processes. Human sediment inputs are based on published minerals statistics. All results are given as first-order approximations. Results: The current sediment deficit in the diked lowlands of the Netherlands is estimated at 136 ± 67 million m3/a. About 85% of this volume is the hypothetical amount of sediment required to keep up with sea-level rise, and 15% is the effect of land drainage (peat decomposition and compaction). The average Holocene sediment input to our study area (based on a total of 145 km3) is ~14 million m3/a, and the maximum (millennium-averaged) input ~26 million m3/a. Historical sediment deficiency has resulted in an unused sediment accommodation space of about 13.3 km3. Net human input of sediment material currently amounts to ~23 million m3/a. Discussion: As sedimentary processes in the Dutch lowlands have been retarded, the depositional system's natural resilience to sea-level rise is low, and all that is left to cope is human countermeasure. Preserving some sort of status quo with water management solutions may reach its limits in the foreseeable future. The most viable long-term solutions therefore seem a combination of allowing for more water in open country (anything from flood-buffer zones to open water) and raising lands that are to be built up (enabling their lasting protection). As to the latter, doubling or tripling the use of filling sand in a planned and sustained effort may resolve up to one half of the Dutch sediment deficiency problems in about a century. Conclusions: Conclusions, Recommendations and Perspectives. We conclude that sediment deficiency – past, present and future – challenges the sustainable habitation of the Dutch lowlands. In order to explore possible solutions, we recommend the development of long-term scenarios for the changing lowland physiography, that include the effects of Global Change, compensation measures, costs and benefits, and the implications for long-term land-use options. Recommendations and Perspectives: -

Background, Aim and Scope - Coastal and river plains are the surfaces of depositional systems, to which sediment input is a parameter of key-importance. Their habitation and economic development usually requires protection with dikes, quays, etc., which are effective in retaining floods but have the side effect of retarding sedimentation in their hinterlands. The flood-protected Dutch lowlands (so-called dike-ring areas) have been sediment-starved for up to about a millennium. In addition to this, peat decomposition and soil compaction, brought about by land drainage, have caused significant land subsidence. Sediment deficiency, defined as the combined effect of sediment-starvation and drainage-induced volume losses, has already been substantial in this area, and it is expected to become urgent in view of the forecasted effects of climate change (sea-level rise, intensified precipitation and run-off). We therefore explore this deficiency, compare it with natural (Holocene) and current human sediment inputs, and discuss it in terms of long-term land-use options.

Materials and Methods - We use available 3D geological models to define natural sediment inputs to our study area. Recent progress in large-scale modelling of peat oxidation and compaction enables us to address volume loss associated with these processes. Human sediment inputs are based on published minerals statistics. All results are given as first-order approximations.

Results - The current sediment deficit in the diked lowlands of the Netherlands is estimated at 136 ± 67 million m3/a. About 85% of this volume is the hypothetical amount of sediment required to keep up with sea-level rise, and 15% is the effect of land drainage (peat decomposition and compaction). The average Holocene sediment input to our study area (based on a total of 145 km3) is ~14 million m3/a, and the maximum (millennium-averaged) input ~26 million m3/a. Historical sediment deficiency has resulted in an unused sediment accommodation space of about 13.3 km3. Net human input of sediment material currently amounts to ~23 million m3/a.

Discussion - As sedimentary processes in the Dutch lowlands have been retarded, the depositional system's natural resilience to sea-level rise is low, and all that is left to cope is human countermeasure. Preserving some sort of status quo with water management solutions may reach its limits in the foreseeable future. The most viable long-term solutions therefore seem a combination of allowing for more water in open country (anything from flood-buffer zones to open water) and raising lands that are to be built up (enabling their lasting protection). As to the latter, doubling or tripling the use of filling sand in a planned and sustained effort may resolve up to one half of the Dutch sediment deficiency problems in about a century.

Conclusions, Recommendations and Perspectives - We conclude that sediment deficiency – past, present and future – challenges the sustainable habitation of the Dutch lowlands. In order to explore possible solutions, we recommend the development of long-term scenarios for the changing lowland physiography, that include the effects of Global Change, compensation measures, costs and benefits, and the implications for long-term land-use options.