The AD tsunami was the most devastating tsunami that affected Atlantic Europe in historical times. In this work we summarize its sedimentological signatures in lowlands Martinhal, Barranco, Furnas, Boca do Rio, Salgados-Alcantarilha of the Algarve coast that contrast in geologic and geomorphological settings and sediment abundance.
We found remarkable similarities between tsunami deposits and the materials available for transport at the coast prior to the tsunami. A number of 2—4 m high and 30—70 m wide scarps i. Recovery of the coastal system to pre-event conditions, inferred from the documentary records, is evaluated and analyzed in terms of sediment availability and supply, climate, hydrodynamic regime and geomorphic setting.
Sediment-starved pocket beaches bypassed landward most of the sediment previously accumulated in the coastal system, failing to recover the pre-event morphology. Moreover, and solely in Martinhal, the abrupt morphological changes translated in increased and lasting permeability of the barrier and adjacent wetland to storms. The Alcantarilha-Salgados beach-dune system, in moderate sand supply, was extensively scarped but not fully overtopped. Here, recovery was partly achieved by destabilization of the remnant dune, formation and limited advance of parabolic dunes following the event.
A schematic conceptual model is presented summarizing: the pre-event conditions; the depositional and geomorphological features directly related with the tsunami impact; and the post-event geomorphological adaptation. In the studied cases post-event recovery seems to be reduced mainly due to a conjugation of pre-event geomorphological setting and low sediment input.
The need to conduct further studies in the impacts of palaeotsunamis is evidenced here, especially because older events allow a large time window to observe post-tsunami adaptation. Costa, M. Oliveira, R. Andrade, M. A healthy natural coastal ecosystem can function as one of the components in reducing potential risk of coastal disasters.
The impacts of tsunamis, storm surges and coastal erosions can be reduced at a certain limit by the existence of coastal forest and dunes.
In Indonesia, tsunami occurs once twice a year in average. It means, tsunami hit quiet frequently even though the return period in a specific location mostly is several tens to hundred years. To reduce potential impacts of tsunamis in coastal area, construction and rehabilitation of coastal forest is one of the main efforts. The existence of a healthy coastal forest not only provides a suitable protection for high frequency but relatively minor to medium scale tsunamis, but also promotes economic activity based on eco-tourism that will ensure the sustainability of the coastal forest maintenance in the later phase.
This paper aims to describe milestones of tsunami mitigation by using greenbelt in Indonesia. Conception, tsunami hazards assessment, challenges and lessons learnt in applying tsunami mitigation by using greenbelt are described so the initiative can be replicated in other tsunami prone areas.
The magnitude and impacts of tsunamis and ocean surges are unpredictable. Careful examination of these events and their consequences provide an insight towards natural protection against these hazards; therefore better preparedness and disaster risk reduction are crucial in countries at risk.
This paper attempts to demonstrate some of the lessons from the December 26, tsunami which struck Sri Lanka, one of the most severely affected countries in the Indian Ocean region. We explored the effects of the tsunami on coastal vegetation in affected areas, and assessed their recovery after the event. We also explored the economic uses of the coastal plants, with the view that plant species with high resilience over tsunami, could be used to establish green barriers against tsunamis and ocean surges while at the same time being of economic value to local communities.
This study revealed that good mangroves were able to stand up against tsunami, helping to reduce the risk. However, mangrove re- forestation should be essentially limited to those areas that are physically and environmentally able to host them and the extent of such areas along the coastline of Sri Lanka is less than one third of the total coastline.
This study also identified non-mangrove species, which could be the potential elements for green barriers along the non-mangrove areas of the coastline. It is noteworthy that all these species except cultivated plants were found to be constituents of the natural seashore vegetation and dune forming vegetation in the past; however, currently their individuals are sparsely distributed probably as a result of anthropogenic pressure. We believe that the direct economic uses of those species as well as the importance of green barriers may motivate dwellers to restore the coastal green barriers along the non-mangrove areas of the coastline.
But with a well-developed and reliable early warning system, and better communication and public awareness, we can minimise the tragic consequences. With earthquakes that occur very close to the beach — often the case in Indonesia — even an ideal system could not disseminate the necessary information quickly enough. This article was originally published in The Conversation. India needs free, fair, non-hyphenated and questioning journalism even more as it faces multiple crises.
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Get help. The graphed data refers only to reefs that remain submerged. A distinctive effect of the earthquake has been the uplifting of coral reefs clear of the water in some locations. The loss of this reef area is additional to the data shown here. On 2nd April a magnitude 8.
The large amount of damage recorded on shallow reefs in the Shortland Islands comprised rolled massive corals and broken branching corals. The tragic and devastating consequences of the Asian tsunami, December , and the hurricanes and cyclones of were a wake up call for the global community, dramatically drawing attention to the dangers of undermining the services that coastal ecosystems provide to humankind. This report has gathered lessons that have been learned since these events that will be relevant to future management of the coasts in the context of severe weather events and other potential consequences of global warming.
More than ever it is essential to consider the full value of ecosystem services that is the benefits that people derive from ecosystems when making decisions about coastal development. The publication aims to help decision and policy makers around the world understand the importance of coastal habitats to humans, focusing on the role of coral reefs and mangroves. As well as coastal protection, it also addresses the huge range of other benefits provided by these ecosystems and the role that they can play in coastal development and in restoring livelihoods for those suffering from the effects of extreme events.
To access this document, click here. The tsunamis of Sunday 26 December caught many people unprepared and unaware in Indian Ocean countries. Our focus in this book is on the impacts on the natural coastal resources, especially the coral reefs and associated ecosystems, and the responses by the international community.
But we cannot ignore that far more damage was done to the lives of people of the region and the world. The tsunamis however were not totally novel and there has been a long history of previous earthquakes and tsunamis in the Indian Ocean.
These are firmly embedded in the folk lore of many indigenous communities, who retreated to higher ground before the waves; most of the victims, however, lacked experience of the potential consequences of earthquakes and tsunamis.
To access the complete document and each chapters, click here. A multinational team of seven scientists and three support crew carried out the Aceh expedition from 17 to 30 October aboard the vessel, Mermaid of the Equator. Starting from Sibolga, the expedition covered the area affected by the earthquakes and tsunami -- over kilometers to Pulau Rondo, the northern-western tip of the Indonesian archipelago.
Unfortunately, high turbidity due to heavy rainfall limited the ability of the team to effectively survey many of the reefs adjacent to the mainland coast. Surveys were carried out using manta tows and the globally-standard Reef Check protocol. The surveys recorded food fish sizes and abundance, as well as mobile and attached invertebrates including corals. A special survey was carried out to detect newly settled corals as a measure of recovery.
The results of the underwater surveys indicated that relatively minor physical damage to coral reefs was caused by the tsunami as compared with the well-documented devastation experienced on land. Tsunami damage recorded included overturned corals and swathes of broken corals where large tree branches and tree trunks had been washed across the reef as the waves receded. No tsunami damage was observed at more than half of the reefs surveyed.
Even in areas where severe tsunami damage was recorded, there were still large areas of intact, living coral reef present nearby. These areas may act as an important source of larvae for recolonization of the damaged reefs.
However, of the 5, quadrats surveyed for recruits, only 18 recruits were recorded, and 15 of these were in the Banyak Island group. This low density of coral recruits indicate that recovery is proceeding very slowly. The earthquake damage to coral reefs was more severe than that caused by the tsunami. Damage included uplifted reefs, shattered beds of coral, and overturned coral colonies. Several islands such as Simeulue were tilted, with one end rising as much as 2 m while the other end descended a similar amount.
This caused tens of hectares of living coral reef to be raised above the high tide level and killed, while other reefs descended into deeper water, altering the ecological zonation.
On land, the earthquakes and tsunami caused slope failures and removed vegetation facilitating increased erosion, sediment transport, and discharge during rainy periods.
A longer-term and more insidious type of reef damage could occur if the observed turbidity and sedimentation continue. In addition to inhibiting coral settlement, sedimentation can directly injure and kill adult corals. A low abundance and small mean size of the ten primary food fish families in Aceh was recorded suggesting that stocks of these fish are overfished. Evidence of destructive fishing practices was common. Overfishing can lead to an imbalanced ecosystem in which the lack of herbivorous fish allows fleshy algae to overgrow corals and dominate the coral reef.
The earthquakes and tsunami have left the Acehenese more dependent than ever on their marine resources for survival. Coral reefs can recover relatively quickly following a reduction in fishing pressure. There is now an opportunity to invest in a long-term strategy to rehabilitate the marine resources of Aceh through education, coastal management, regular monitoring and the establishment and maintenance of marine protected areas.
To access this important and interesting document, click here. Excerpt from the report "The effect of the tsunami on corals was highly dependent on habitat, although within habitats the geomorphology of the coastal zone was also important. West facing coral reefs with shallow slopes incurred greatest damage, however corals attached to solid substrata in the shallows m depth , generally incurred little damage. We detected no significant change in shallow coral assemblages between March and March , with the exception of one site smothered by sediment.
Many sites remain in excellent condition, particularly on Pulau Weh, where local management has proved effective. An exception to this pattern was on the southern edge of the fringing reef of Lampuuk, where a previously flourishing Acropora assemblage has been smothered by sediments, most likely of terrestrial origin.
The change in sediment regime and increased turbidity following the tsunami, particularly on the west coast reefs of the Acehnese mainland, continues to threaten corals, with some bleaching evident, possibly as a consequence of low light.
A survey was conducted by Active Fault Research Center, Japan and Myanmar Government agencies to look at Tsunami heights and damage along the Myanmar coast from the December Sumatra-Andaman earthquake, found that tsunami heights along the Myanmar coast were not more than 3 m and the affected time was mostly between and , that is 2 to 5.
Excerpt from the report "Tsunami was generated in the fast slip area first km at taut length and the waves propagated in all directions. The propagation of tsunami waves is much stronger in east-west direction than north-south direction.
Further, due to slow slip in the remaining northern areas, it appears that no tsunami was generated there. As a result, strongest waves hit the coasts of Thailand, Indonesia and other nearby areas which are closely located on the east of the epicenter.
The intensity of these tsunami waves that hit along the coastline of Orissa and Andhra Pradesh was weak due to their diagonal propagation. However, southern east coast of India and Sri Lanka experienced much stronger tsunami waves due to their location in mere western side of epicenter.
Though the Palk Strait and further southern areas of Tamilnadu are shadowed by Sri Lanka, the waves refract around island and inundated these coastal areas. The damage to Kerala coast on the west coast of India is also due to this wave refraction beyond Kanyakumari". To access full paper of this detail report, click here.
Rapid and detailed post-tsunami surveys was carried out in the Langkawi archipelago in January showed that the coral reefs did not suffer any significant structural damage. Nevertheless, there were signs of recent sediment resuspension at the sites studied. The diversity and abundance of coral reef fishes and invertebrates were low. However, this was not attributed to the tsunami effect but rather to the present environmental conditions. The extent of damage at the villages of Kubang Badak and Kuala Teriang may indicate that intact coastal ecosystems such as mangroves have the potential to protect lives and property during natural disasters.
To access full paper of the report, click here. Gerald R. Allen was included into ReefBase literature section. Excerpt from the article: "The reef next to Iboih Village presented a rare opportunity to study the effect of the tsunami on reef fish populations. Although about 75 percent of the reef was destroyed, two mainly undamaged sections provided a baseline of sorts for comparisons. We laid a measuring tape on the bottom running perpendicular from shore and counted every fish within two metres of the tape and also estimated their total biomass using length-weight data.
The experiment was repeated four times, two times each on heavily damaged and lightly impacted sections of reef. Slightly over twice as many species and almost five times as many individuals were found in the lightly impacted areas compared to the severely impacted ones.
Moreover, the lightly impacted sections had a biomass value that was about four times greater than that of the severely impacted areas. There is no doubt that the tsunami had a profound impact on local fish communities. Certainly the most dramatic impact we witnessed was at Gapang Lagoon and near Iboih Village. In both instances the entire reef was scoured clean leaving only the basement rocks that formed the foundation of the former living reef.
The adjacent debris fields are oddly reminiscent of the tsunami refugee camps seen around the outskirts of Banda Aceh. NPS Photo. Hawai'i A tsunami generated by a magnitude 9.
American Samoa In the 8. Tsunami zone markers near Redwood National Park, California. Tsunami Safety Tsunamis may eventually visit every coast in the Pacific Ocean due to high seismic activity. Here are some facts and safety tips about tsunamis you should know: Tsunamis are a series of waves commonly caused by an earthquake beneath the sea floor. They can last for many hours, and the first wave is often not the largest.
If you are on a beach or in a harbor and feel an earthquake, no matter how small, immediately move inland or to high ground. Beaches, harbors, lagoons, bays, estuaries, tidal flats and river mouths are the most dangerous places to be in a tsunami.
You may not receive a warning for a locally-generated tsunami.
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