HoLFloods – MID-LATE HOLOCENE FLOOD EVENTS IN SOUTH-EASTERN AND CENTRAL ROMANIAN LOWLANDS

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PROJECT SUMMARY AND OBJECTIVES

Project summary

In light of observed and projected increases in hydrological extremes and flood risk in Central-Eastern Europe, understanding long-term flood patterns and drivers becomes imperative for predicting flood frequency, magnitude and impacts in the Romanian lowlands. Longer and better resolved time series that extend beyond available instrumental records are thus needed to capture the full range of hydrological variability. In this context, this project aims to reconstruct flood patterns and quantitative flood frequency/magnitude in two distinctive Romanian lowland areas (north-eastern Transylvania and south-western Dobrogea) for the mid-late Holocene (last 6000 years), using two high-resolution lacustrine archives. Further, new paleoclimate and paleo-vegetation/fire reconstructions will be provided to assess the long-term role of climate and land-use as drivers of flood occurrence. The project will use a multi-proxy, interdisciplinary approach which integrates novel and established methods to extract the palaeoflood history (abiotic sediment properties, catchment fingerprinting), calibrate flood chronology (sediment traps, gauge station/meteorological data, documentary data, novel statistical methods) and reconstruct climate and land-use controls (GDGT palaeothermometry, leaf-wax n-alkanes as proxy for dry conditions; pollen, charcoal, dung fungal spores and archaeological information as proxies for land-use change and anthropogenic disturbance). The estimated results will potentially contextualise local to regional flood frequency/magnitude estimates and mechanistically explain long-term patterns of flood occurrence and thus provide reliable assessments of flood-related risks to ecosystems and infrastructure.

Project Number: PN-III-P1-1.1-TE-2019-1628
Funded By: UEFISCDI
Host Institution: Ștefan cel Mare University, Suceava

Objectives

1) Develop the sedimentary palaeoflood records based on the two high-resolution lacustrine archives.
Research questions: Which are the stratigraphical signatures of discrete flood layers in the two sediment records? How were flood-rich and flood poor phases distributed over the mid-late Holocene? Are there regional flood patterns, i.e., common between the two sites, and /or synchronous with patterns in Central and Western Europe?

2) Calibrate the flood chronology against independent river flow and meteorological data (last 50/100 years), sediment traps (1-1.5 years) and documentary information (last 500 years); followed by incorporation of the palaeoflood record in the frequency/magnitude analysis.
Research questions: Which is the discharge/precipitation threshold (mc/s; mm) which controls the flood unit preservation? Is there any relationship between flood layer thickness and the magnitude of river discharge / precipitation amounts? What is the frequency/magnitude of mid-late Holocene palaeoflood events? Are the flood events of the last 50/100 years in Romania unprecedented?

3) Explore the medium to long-term climatic and land-use related drivers of flood occurrence (including disturbances by fire, grazing, clearance), using new and published palaeoclimatic information.
Research questions: Do warmer and/or drier periods correspond to higher frequency and/or magnitude of flood events? How do flood-rich/poor phases relate to Rapid Climate Changes? Do atmospheric modes and pressure systems (e.g., North Atlantic Oscillation, Atlantic Multidecadal Oscillation, Siberian High) and/or solar activity exert some control over the timing and duration of regional flood rich/poor phases, over flood frequency and/or magnitude? Are there particular human activities/disturbances that correlate with flood-rich/ poor phases? Has flood frequency/magnitude increased with land-use change and extension of settlements?

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