Driving factors for and societal effects of sea-level rise and delta flooding in the Ayeyarwady Delta (Myanmar) – Lessons from the past for disaster governance in the future
Principal Investigator(s): Dr. Dominik Brill, Prof. Dr. Helmut Brückner, Prof. Dr. Frauke Kraas
Substantiated by historical observations and model predictions, it has been accepted that coasts, in particular densely populated delta areas, currently face an unprecedented acceleration of global sea level rise (SLR). In combination with subsidence in large deltas, SLR will furthermore exacerbate the negative effects of delta flooding due to combinations of tropical cyclone-induced river floods and storm surges. The regional focus of the project is the Ayeyarwady Delta which will be strongly affected by the entire spectrum of SLR-related hazards. Its high vulnerability was exemplified by Cyclone Nargis in 2008, which triggered a 5-m storm-surge with extensive flooding, leaving 138,400 dead and missing. Storm-induced river floods also affect higher delta parts; for example during cyclonic storm Komen in Aug 2015 >3 M people in Myanmar were affected, particularly along the Ayeyarwady River. Both Nargis and Komen were disasters unprecedented in history. The uniqueness of the project lies in its research area and in its design which links the sedimentary and historical records of past SLR and delta flooding events (DFE) with the socio-economic development of the region. The interactions between SLR, DFE, and societal impacts shall be exemplified for six sites within the Ayeyarwady Delta, with the four most promising sites studied in-depth over different timescales. Using a combination and mutual interpretation of data from physical and human geographical research, natural and human drivers for SLR and DFE and their consequences shall be identified.
In Part 1 (1988 to present, i.e. the period of marked-oriented economy) and Part 2 (1860–1988, i.e. the period since the beginning of delta colonization), high-resolution records of SLR and DFE shall be studied. Sea level reconstruction will be based on tide and river gauge data, which for the first time ever will be made available internationally. For the reconstruction of historical to modern DFEs, a combination of high-resolution sedimentary records and historical archive data shall be used. By combining SLR and DFE frequencies with data on land-use, landscape changes, population density and socio-economic developments in the delta area derived from historical archives and expert and household interviews, the human response to SLR and DFEs shall be investigated. In Part 3 (i.e. the period prior to delta colonization in 1860), long-term SLR and DFE frequency-magnitude patterns during the last few millennia will be investigated based on sedimentary records. The synergetic analysis of these data will ultimately help to understand how and to which extent SLR and DFE affected the socio-economic development in the Ayeyarwady Delta and vice versa. Since Myanmar has nearly been a terra incognita for many decades, we assume that these findings are highly relevant for improving present hazard assessment, and for developing future strategies of mitigation and risk governance.
CRC: Earth-Evolution at the Dry Limit
Subproject D05: OSL-Dating. Constraining the Pleistocene environmental history of the Atacama: Extending the age range of luminescence dating
Principal Investigator(s): Prof. Dr. Helmut Brückner (Köln), Prof. Dr. Georgina King (Lausanne)
Projektmitarbeiter: Dr. Dominik Brill, Dr. Alicia Medialdea
A new Collaborative Research Centre (CRC) led by Prof. Tibor Dunai from the Institute of Geology and Mineralogy at the University of Cologne titled “Earth-Evolution at the Dry Limit” was funded by the DfG in August 2016. This CRC seeks to explore the mutual evolutionary relationships between Earth surface processes and biota, through focussing on the Atacama desert. The CLL (sub-project D05) has been awarded c. 360k € to contribute to the CRC both by providing chronologies to the different sub-projects, and also through developing new techniques capable of extending the age range of luminescence dating. Specifically the CLL has been awarded funds to purchase a new Risø luminescence reader capable of measuring violet stimulated luminescence, which other researchers have shown may enable timescales in excess of 1 Myr to be dated (e.g. Ankjaegaard et al., 2015).
CRC 806 (Phase 3): Our Way to Europe – Culture-Environment Interaction and Human Mobility in the Late Quaternary
Section F2: Application of Luminescence and Electron-Spin-Resonance Dating in Geoarchaeological Studies
Projektleiter: Prof. Dr. Helmut Brückner, Dr. Dominik Brill
Projektmitarbeiter: Dr. Nicole Klasen, Lucas Ageby
Dating techniques will be further developed and tested which are urgently needed for gaining reliable age-models for the different archives the CRC relies on. Convincing results of 14C, OSL and paleomagnetic based age models were developed during the second funding period (i.e. for the Chew Bahir 40m core). For the third funding period we would therefore continue with the development of these techniques, because they represent the backbone of the age models used for all our archives. The interplay and cooperation of the three subproject guarantees the development of age specific models towards a better understanding of the environmental and cultural history along the migration routes of AMH. Subproject F2 aims at improving the single grain OSL method for cave sediments. A further step towards a refining chronology of archaeological sites is to include the dating of rock surfaces from pebbles of rock shelter deposits with OSL. Rock shelters play a major role in excavating archaeological findings in our CRC 806 project and are often hard to date, especially for times older than 40 ka, the time frame without the use of radiocarbon dating methods. Therefore, the aim of F2 is a basic need and will certainly help to better understand sedimentation processes in rock shelters.
Estimation of the regionally differentiated coastal subsidence for southwestern Bangladesh from submerged historical kilns and associated mangrove stump horizons
Projektleiter: Prof. Dr. T.J.J. Hanebuth (MARUM, Universität Bremen)
Projektmitarbeiter: Dr. Anja Zander
- Prof. Dr. Kudrass (MARUM, Universität Bremen)
- Dr. G. Neumann-Denzau
Förderung: DFG (HA4317/8-1)
The aim is to study the subsidence history over an estimated period of 500 years and along 60 km east-west extension along the coast of the Sundarbans mangrove forest. For a robustunderstanding, the architecture of recently discovered rounded kilns at the lower position near Gawbonia and the distribution pattern of the mangrove paleo-stump horizons are investigated.
- Hanebuth, T.J.J., Kudrass, H.R., Linstädter J., Islam B., Zander, A., 2013. Subsidence of the outer Ganges River Delta, Bangladesh, during the past 300 years deduced from drowned salt‐refining sites. Geology, 41 (9), 987-990.
OSL surface exposure dating of wave-emplaced boulders – improving the use of coarse-clast records for coastal hazard assessments
Principal Investigator(s): Dr. Dominik Brill, Dr. Simon Matthias May
Fields of wave-emplaced blocks and boulders represent impressive evidence of cyclone and tsunami flooding over Holocene time scales. Unfortunately, their use for coastal hazard assessment is impeded by difficulties in the differentiation of tsunami- and storm-transported clasts, and by the absence of appropriate and accurate dating approaches, which are needed to generate robust chronologies of coarse clast records. The commonly applied AMS-14C, U/Th or ESR dating of coral-reef rocks and marine organisms attached to the clasts depends on a – mostly hypothetical – coincidence between the organisms’ death and boulder displacement, and inferred event chronologies may be biased by the marine 14C-reservoir effect and reworked organisms. The research proposed here addresses the necessity of innovative approaches to date the transport of coastal boulders by testing the recently developed optically stimulated luminescence (OSL) surface exposure dating technique. By measuring the depth-dependent resetting of the luminescence signal in exposed rock surfaces and comparing it to the signal-depth profiles of known-age samples, OSL surface exposure dating is capable to model direct depositional ages for boulder transport. Thereby, it promises to overcome the limitations of existing dating techniques, and to decipher complex transport histories of clasts that underwent multiple phases of exposure and burial.
The successful application of OSL surface exposure to rock surfaces in archaeological contexts suggests that candidate coarse-clast records should be characterized by (i) overturned boulders that are exposed for periods shorter than the expected dating range of ~10-100 ka; (ii) a boulder lithology with significant percentages of quartz or feldspar appropriate for OSL dating; (iii) limited erosion of the exposed boulder surfaces; and (iv) known-age rock surfaces of the same lithology to calibrate site-specific model parameters (i.e. the local light flux at the rock surface). Our study site at Cabo de Trafalgar (Cádiz, Spain) offers all of these preconditions. Storm and/or tsunami waves have deposited up to 7 m-long clasts composed of Pleistocene beach rock on the inter- and supratidal platform, and multiple dislocation is assumed for numerous smaller clasts. We thus aim at dating boulders with single and multiple dislocation. Recently exposed rock surfaces, ancient buildings as well as quarries provide surfaces of known exposure age. The use of artificially exposed rock samples (for periods of 1 and 2 years) as reference samples for model calibration shall be evaluated. In the best case, the proposed investigations shall not only test the general suitability of the approach to coastal boulders but also provide quantitative information about the frequency-magnitude relationship of extreme wave events at Trafalgar. Thereby, it will allow to verify or falsify a correlation with the 1755 Lisbon tsunami, which is assumed for the largest clasts.