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Über dieses Buch

This monograph is a compilation of a number of research studies presented in fourteen chapters dealing with the impact and restoration of coastal environments that have been affected by earthquakes and tsunamis. The focus is mainly on rivers, estuaries, coastal lagoons, beaches, and related ecosystems. In addition to direct impact and response due to flooding and subsequent abrasion, this publication covers physical, chemical and biological responses in coastal morphology, water quality and ecosystems and includes also topics dealing with risk reduction and vulnerability.

This compilation mainly covers examples from large magnitude earthquake and tsunami events in the Indian and Pacific Ocean that are complemented with other events in Latin America and the Iberian Peninsula.

Comprehensive descriptions of multi-scale impacts of tsunami and earthquake events, both spatially and temporally, will help the reader to understand the complicated interactions which occur in coastal zones in order to create a sustainable, resilient environment and achieve a society with smart post-event recovery planning. This book is aimed at researchers and students in coastal science and engineering as well as at policy makers, environmental planners and coastal managers.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Revisiting the 2001 Peruvian Earthquake and Tsunami Impact Along Camana Beach and the Coastline Using Numerical Modeling and Satellite Imaging

Abstract
On June 23, 2001, a moment magnitude Mw 8.4 earthquake occurred off the southern coast of Peru causing substantial damage to urban and agricultural areas. The tsunami generated by this earthquake reached up to 7 m run-up height and extended over 1.3 km inundation. This paper aims to revisit the impact of the 2001 Peruvian tsunami on the coastal area and its morphology along Camana city. The tsunami source is reconstructed through inversion of tsunami waveform records observed at several tide gauge stations and the impact is analyzed using the numerical result and moderate-resolution satellite images to calculate the inundation features in the coast. Finally we propose the tsunami source model suitable for further analysis of this event through tsunami numerical simulations. In addition, environmental changes, in particular the impact to vegetation areas, were evaluated using satellite imagery. An important reduction of agricultural areas due to tsunami impact and soil salinization was confirmed.
Bruno Adriano, Erick Mas, Shunichi Koshimura, Yushiro Fujii, Hideaki Yanagisawa, Miguel Estrada

Chapter 2. Imprints of the AD 1755 Tsunami in Algarve (South Portugal) Lowlands and Post-impact Recovery

Abstract
The AD 1755 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.e. steep slopes in dunes resulting from erosion) are the only erosive geomorphic signature preserved in the study areas (Boca do Rio and Salgados-Alcantarilha). 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 1755 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.
P. J. M. Costa, M. A. Oliveira, R. González-Villanueva, C. Andrade, M. C. Freitas

Chapter 3. Ecosystem-Based Tsunami Disaster Risk Reduction in Indonesian Coastal Areas

Abstract
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.
Eko Rudianto, Abdul Muhari, Kenji Harada, Hideo Matsutomi, Hendra Yusran Siry, Enggar Sadtopo, Widjo Kongko

Chapter 4. Post-Tsunami Assessment of Coastal Vegetation, with the View to Protect Coastal Areas from Ocean Surges in Sri Lanka

Abstract
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, 2004 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.
L. P. Jayatissa, K. A. S. Kodikara, N. P. Dissanayaka, B. Satyanarayana

Chapter 5. Shoreline and Coastal Morphological Changes Induced by the 2004 Indian Ocean Tsunami in the Katchal Island, Andaman and Nicobar – A Study Using Archived Satellite Images

Abstract
The December 24, 2004 Sumatra earthquake and Tsunami had caused large damage to the coastal environment in the Indian Ocean countries. Continuous monitoring of shorelines are needed to understand the causes and consequences of recent changes and to assess the long term impact of tsunami waves. Assessment of the shoreline and coastal morphological changes due to tsunami in Katchal Island have been lacking due to obstacles in the field data acquisition owing to their remote location. As access to the ground information is limited, the only possibility is the monitoring of shorelines from multi-temporal satellite images.
In this study, we demonstrate the methods used in extracting shorelines and analyzing their changes using the data from Indian Remote Sensing (IRS) satellites, the EO1-ALI and Landsat images in a GIS environment. Eight satellite images acquired between 2004 and 2014 where used for the shoreline change and coastal morphology analysis in the Katchal Island. The results showed that the island experienced extensive erosion and significant loss in land area of about 20 km2. Erosion has been more prevalent than accretion at an average linear regression rate of ~ −13 m/year between 2004 and 2010. Net shoreline movement of more than 4 km landward has been observed at the western coast of the island. Regions of high net shoreline movements were associated with bay-mouth areas, and regions linked with coastal inlets. This study demonstrates the strong potential of archived satellite images for detecting shoreline movements in far-off islands. The results will likewise help in understanding the response and recovery of shorelines in Indian Ocean regions after the 2004 tsunami.
Ali P. Yunus, Jie Dou, Ram Avtar, A. C. Narayana

Chapter 6. Mud Volcanoes in an Active Fore-Arc Setting: A Case Study from the Makran Coastal Belt, SW Pakistan

Abstract
The Makran coastal belt is over 1000 km long stretching from Iran to east of Karachi in Pakistan. A major active subduction zone known as Makran subduction zone defined by the under thrusting of the Arabian plate beneath the Eurasian plate runs parallel to the coastline. The subduction zone is associated with a thick accretionary sedimentary wedge deposited in an active fore-arc basin containing very thick detrital sediments contributed by the accretion of the subducting plate since Late Eocene time. The sediments in the fore-arc basin are fine-grained usually of clay size fraction deposited in highly fluidized conditions trapping methane gas. The fluidized mud diapirically moves upward along weak zones as mud volcanoes due to high sedimentation rates and escaping gas pressure piercing through the overlying sediment layers. The development of mud volcanoes shows a close relationship between the sedimentation rates, gas escape from sediments and tectonic activity. Mud volcanoes are found in abundance both onshore and offshore of the Makran Coast. Most of the onshore mud volcanoes are associated with active fault zones and are believed to be triggered by tectonic activity. Located in the hanging wall of an active subduction zone, the region is seismically highly active and occurrence of major earthquakes exceeding magnitude 7 is a common phenomenon (e.g., Mw = 7.7 2013 Awaran, Mw = 8.2 1945 Makran). The seismic activity of this scale is likely the major triggerer for the emergence of new islands off the Makran coast in the Arabian Sea on regular basis in the past history. The latest of these emerged in 2013 immediately after the Mw = 7.7 Awaran earthquake.
In this chapter we review major mud volcanoes formed along the Makran coastal region by describing their distribution, evolutionary history and mechanism of their formation. The chapter also describes the sudden appearance of islands off Makran coast since 1945 major earthquake and their importance in the geological history of the coastal regions.
Iftikhar Ahmed Abbasi, Din Mohammed Kakar, Mohammed Asif Khan, Ahmed Sana

Chapter 7. Response of Sheltered and Built-up Coasts in the Wake of Natural Hazards: The Aftermath of the December 2004 Tsunami, Tamil Nadu, India

Abstract
The geomorphology and the disposition of natural features and type of coast are major factors that control wave heights and govern consequent inundation distances. The connection between tsunami run-up heights and inundation of the hinterland is attempted. Field observations carried out in the aftermath of the December 2004 tsunami reveals that there is no direct relationship between the tsunami run-up height of the incoming wave and the flooding it causes. Coastal sand dunes and forested ecosystems dissipated wave energy during the tsunami event. In comparison, flat and built-up coasts devoid of natural protection suffered maximum damage. Post tsunami restoration initiatives have ignored environmental guidelines.
Jaya Kumar Seelam, Antonio Mascarenhas

Chapter 8. Characteristics of Shoreline Retreat Due to the 2011 Tohoku Earthquake and Tsunami and Its Recovery After Three Years

Abstract
We investigate the characteristics of shoreline retreat due to the 2011 Tohoku Earthquake and Tsunami and its recovery after 3 years over a wide area from Aomori Prefecture to Ibaraki Prefecture by analyzing the data of crustal deformation, tsunami height, and aerial photographs. There were no significant retreats where the seawall remained unbreached and where river mouths were distantly located regardless of the tsunami overflow depth over the seawall, indicating that the seawall condition during tsunami strikes is one of the most important factors that prevent serious shoreline retreat. After 3 years from the event, recovery of the eroded Ria coasts has been insignificant compared to the plain coasts. The key natural factors for the recovery are the upward crustal deformation after the earthquake and sediment supply from adjacent coasts or rivers after the tsunami; however, these could not be expected at the Ria coasts at least in near future.
Keiko Udo, Kaoru Tojo, Yuriko Takeda, Hitoshi Tanaka, Akira Mano

Chapter 9. Investigating the 2011 Tsunami Impact on the Teizan Canal and the Old River Mouth in Sendai Coast. Miyagi Prefecture; Japan

Abstract
This study investigates the effect of old river mouth and the Teizan Canal to the 2011 tsunami at Arahama and Akaiko, both part of Sendai Coast, Japan. At both locations, the Teizan Canal is situated parallel to the shoreline. This canal affected the tsunami inundation as well as the return flow, effectively draining the water back to the sea. In addition, there were old river mouths, which have been closed for many years in these locations. Nevertheless, the return flow of the 2011 tsunami caused the breaching of the sandy coast at the old river mouth locations. A detail topography analysis was carried out based on DEM data. The topography data show that this area is a river basin with mild slope towards the old river mouth location. The data was further analyzed by performing a flow accumulation analysis using GIS. The results confirm that the topographical features in both locations caused the flow to accumulate through the local channel and canal towards the locations of the old river mouth, which caused the breaching.
Mohammad Bagus Adityawan, Hitoshi Tanaka

Chapter 10. Morphological Characteristics of River Mouths After the 2011 Tohoku Tsunami in Miyagi Prefecture

Abstract
Coastlines and river mouths along the Tohoku Region in Japan are in the process of steady recovery following the 2011 Tsunami. The affected sandy coastlines and river mouths have undergone more significant changes than the corresponding cliffs, rocky beaches, and hard structures. Analyses of aerial photographs and topographic data related to pre-tsunami and post-tsunami conditions together with the estimated minimum width and positioning changes of river mouths describe how they have changed as well as the differences in their recovery processes. In many cases, there is an indication of stable recovery although the behavioral tendency differs, as in the case of the Natori and Naruse rivers. This study shows that the temporal topographic changes and the relationship with the tidal prism in the mouths of these river mouths differ, resulting in different sediment deposition and restoration processes. Sediment supply is intricately associated with the morphological changes in river mouth morphological changes, which in turn reflect on its recovery. The morphological changes in a river’s mouth present practical river management and maintenance problems in ports and harbors; consequently, continuous monitoring is essential.
Min Roh, Yuta Mitobe, Hitoshi Tanaka

Chapter 11. Post-Tsunami Lagoon Morphology Restoration Sendai; Japan

Abstract
The 2011 Great East Japan Earthquake and Tsunami caused significant changes of morphology of Gamo Lagoon which is located in the northern part of Sendai Coast, Miyagi Prefecture. The investigation on the morphology changes and its recovery process after the tsunami are discussed. Frequently captured aerial photographs are effectively utilized to analyze detailed morphological changes in response to wave action after the tsunami. The lagoon area was greatly changed due to the 2011 tsunami, and a gradual process of river mouth changes and restoration were observed using aerial photographs. As compared with the shoreline position before the tsunami a 40 m retreat of the shoreline can be confirmed even after 3 years from the tsunami. Meanwhile, the water area shows distinct reduction by 40 % as compared with the pre-tsunami situation. Gamo Lagoon is well known not only having important roles in the coastal processes but also valuable brackish water environment, hence further investigation is also largely required to better understand the future state of the devastated coastal environment by the tsunami waves.
Vo Cong Hoang, Hitoshi Tanaka, Yuta Mitobe

Chapter 12. The Minato River in Miyagi Prefecture Reconstruction and Restoration – An Overview

Abstract
On March 11, 2011 (Heisei 23) a large earthquake and tsunami hit the coastline along Miyagi Prefecture, Japan, with catastrophic consequences by heavily impacting beaches, lagoons, wetlands, rivers and estuaries. The lower watershed of the Minato River (Minatogawa) and its mildly urbanized estuary, as well as the surrounding area, suffered heavy damage due to ground subsidence, sediment deposition, wave erosion, abrasion and flooding. Local authorities developed plans for reconstruction and rehabilitation of the river and its estuary. Work started in earnest by 2013, which included the construction of a L1 type levee. The impacts of the engineering-related works and structures to be built are expected to be large, particularly for the levee, likely putting in doubt their environmental sustainability.
Vicente Santiago-Fandiño, Naoko Kimura

Chapter 13. Tsunami Impacts on Eelgrass Beds and Acute Deterioration of Coastal Water Quality Due to the Damage of Sewage Treatment Plant in Matsushima Bay, Japan

Abstract
The 2011 tsunami in Japan severely disturbed the benthic biota in Matsushima Bay (Miyagi Prefecture) via sediment erosion. Eelgrass beds markedly decreased from their original coverage of 2.2 km2 in June 2007–0.02 km2 in May 2012. Although our monitoring indicates that the eelgrass beds are slowly recovering, an analysis based on a Habitat Suitability Index model suggests that their recovery is restricted by deteriorated light conditions due to land subsidence resulting from the prior earthquake. Additionally, the tsunami severely damaged a sewage treatment plant adjacent to the bay, and this led to acute increases in chemical oxygen demand and coliform bacteria in the seawater. However, the water quality improved when the damaged sewage treatment plant started temporary operations, such as sedimentation, aeration, and chlorination, and recovered to pre-tsunami conditions in approximately 1.5 years. These results demonstrate that temporary treatment methods are important to minimize acute impacts of treatment facility damage on water environments.
Takashi Sakamaki, Youhei Sakurai, Osamu Nishimura

Chapter 14. Effects of the Great East Japan Tsunami on Fish Populations and Ecosystem Recovery. The Natori River; Northeastern Japan

Abstract
The tsunami following the Great East Japan Earthquake in March 2011 resulted in significant ground subsidence and deposition of rubble and mud in the Natori River, near the city of Sendai (Miyagi Prefecture), damaging its brackish water ecosystem and fishing grounds. There was a direct impact in the form of annihilation of animal and plant life and disturbance of the habitats throughout. Also, a wedge of seawater ran far upstream, and ground subsidence changed the pattern of tidal flow in the river. Brackish water ecosystems such as that near the mouth of the Natori River are important as nurseries for juvenile fishes and as a fishing ground for bivalves such as clams. The populations of both of these kinds of organism declined drastically as result of the tsunami. The catch per unit effort of ayu fish (sweetfish; Plecoglossus altivelis altivelis) in 2011 was the lowest recorded for the past 5 years, and the population hatching date composition showed a marked absence of early-hatched individuals. In contrast, the residual upstream ayu fish population seems to have grown successfully and reproduced despite the effects of the tsunami: 1 year after the tsunami occurred, the downstream ayu fish population had recovered to the same level as before the event. However, the population of the brackish-water clam, Corbicula japonica, only showed recovery 2 years after the disaster as its habitat has drastically shifted due to movement of the brackish water zone about 1 km upstream. The studies reported here show that the impact of the earthquake and tsunami on pelagic fish and benthic bivalves seems to have been quite different, as in the former recovery was rapid, while in the latter it took much longer. Many other fish species also returned to normal levels within a year, such as stone flounder (Kareius bicoloratus), goby (Acanthogobius lactipes), icefish (Salangichthys microdon) and black porgy (Acanthopagrus schlegelii). The food web structure appears to be slightly different from past years, but the results show that, in general, fish communities are able to recover rapidly from disturbances even as drastic as an unusually large tsunami.
Kinuko Ito, Ayu Katayama, Kazunori Shizuka, Norihiro Monna

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