GM3.3/CL65/HS13.03/NH2.4

Flooding and climate during the last two millennia (co-organized)
Co-Conveners: Dr Macdonald , RC Chiverrell 
Oral Programme
 / Thu, 23 Apr, 13:30–15:00  / Room 19
Poster Programme
 / Attendance Thu, 23 Apr, 17:30–19:00  / Hall A
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The prediction of extreme floods in response to global warming is one of the major uncertainties in the IPCC (2007) report. Flood frequency and magnitude are controlled by a myriad of factors including precipitation (intensity and duration), antecedent conditions, snowmelt, land cover and channel/floodplain morpho-dynamics. Under some IPCC scenarios it is likely that floods occurring within Europe will increase in frequency and magnitude due to warming and increased atmospheric moisture. Evidence from sedimentary and documentary records of palaeofloods indicates that cold (and sometimes dry) periods of the Little Ice Age were characterised by floods of greater magnitude than observed during the instrumental period. In part this may be due to increased snowmelt, but other explanations include: changes in the frequency of flood-producing circulation patterns; increased frequency in blocking high/low pressure systems located over central Europe; fluctuations in the North Atlantic Oscillation (NAO); or changes within Atlantic storm tracks. There is also increasing evidence to suggest that the period spanning 800-1200 AD was one of greater flooding, but whether this is in response to warming associated with the Medieval Warm Period or colder phases is not yet known due to geochronological uncertainties in the flood record.

This session aims to bring together an interdisciplinary spectrum of scientists from across the Geosciences (geomorphology, hydrology, meteorology/climatology, geoarchaeology and environmental history) to examine and discuss our understanding of the relationships between flooding and climate for the last 2000 years. Past perspectives over this duration of timescale are critical for developing a robust understanding for the future. In particular the focus of the session will be multi-proxy reconstructions of:
a) Climate and event-based meteorology (e.g. temperature and moisture, NAO);
b) Flood magnitude and frequency;
c) Human impacts on flood frequency and magnitude;
d) Archaeological and/or historical evidence of societal response to flooding;
e) External forcing on flooding (e.g. solar activity, volcanic aerosols).
Incorporating a wide range of evidence from sediments and landforms, historical documents, (geo)-archaeological records and long term measurement series, alongside the application of modelling approaches, will ensure the desired multidisciplinary cross-spectrum of scientific interests.

This session has 2 sponsored keynote presentations with support from the British Hydrological Society and the British Society for Geomorphology/Earth Surface Processes and Landforms.