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On the 17th, 19th and 23rd of July 2007, a series of local thunderstorms induced flash floods in the upper part of the South Tyne river in Northumberland, a rural area located near the border between England and Scotland. These events led to moderate damages in the villages and losses of livestock in local farms. They were shadowed in comparison to the widespread lowland floods that occurred throughout the UK during the same period but were nevertheless extreme events for the region. One of the affected streams, the Thinhope Burn, has been surveyed by the University of Gloucestershire during recent years. It is an active river from a geomorphological point of view. A survey conducted after the 2007 flood revealed that many of the boulders along the banks of the river, which had been deposited 50 to 100 years before, had been displaced, indicating a high return period for the flood (see EGU abstract EGU2008-A-04713). A complementary survey was conducted in July 2008 with the objective of gathering information on the discharges, the rainfall amounts and the active runoff processes. 14 cross-sections were surveyed, pictures were collected enabling a validation of peak discharge estimates, 5 witnesses were interviewed and additional rainfall data and geomorphological evidence were collected. This survey revealed that the peak discharges exceeded 5 m3/s/km2 in the most affected areas. Unfortunately, no rainfall measurements are available that would enable further analysis, including the computation of runoff rates. Nevertheless, witness accounts and field observations give a good insight into the hydrological processes indicating a significant initial storage capacity of the peat layer covering the affected watersheds. Concerning the boulders, the field observations suggest surprising and unexplained transport processes. Blocks of up to one meter diameter were displaced over short distances and deposited on the river banks without any sign of established debris flow, as if short debris pulses occurred along the river course. This work is conducted within the European research project HYDRATE (Contract GOCE 037024).

Flash floods are one of the most significant natural hazards in Europe, and can cause damage to buildings and infrastructure and pose a high risk to life. Existing inventories of past floods give information for other geographical regions or lack quantitative information on the meteo-hydrological and hydraulic characteristics of the event. The lack of centralised national and international databases for storing meteo-hydrological, hydraulic and socio-economic data relating to past flood (and particularly flash flood) events within Europe means that it is difficult to calibrate and validate research results on a range of previous floods from different climatic regions. To address this apparent gap in availability of centrally stored, high quality data and with the aim of supporting research on risk assessment and ?ash flood forecasting, a data base has been developed that collates flash flood data from seven European hydrometeorological regions and that could be extended in the future to other areas. Compilation of the database required the development of a data template and flood event selection rules. Initial analyses of the data highlight spatial variations of flood hazard magnitude, with highest speci?c peak discharges in the Mediterranean region. There is a strong seasonality to the occurrence of events, with events occurring mostly in the autumn in the Mediterranean region and in the summer in middle and eastern European regions. There have been flash floods in France and Spain on a basin scale of greater than 500 km2 . This work has been carried out for HYDRATE, which is a currently ongoing EC funded project that is aiming to improve techniques for flash flood forecasting. The work presented here represents some of the first outputs from this project.