CHANNEL AND FLOODPLAIN RESPONSE TO RECENT ABRUPT CLIMATE-CHANGE - THETYNE BASIN, NORTHERN ENGLAND

This paper examines the timing, nature and magnitude of river response in upland, piedmont and lowland reaches of the Tyne basin, northern E ngland, to high-frequency (20-30 year) changes in climate and flood re gime since 1700 AD. Over this period fluvial activity has been charact erized by alternating phases of river-bed incision and stability coinc iding with non-random, decadal-scale fluctuations in flood frequency a nd hydroclimate that appear to be linked to changes in large-scale upp er atmospheric circulation patterns. Episodes of widespread channel be d incision (1760-1799, 1875-1894, 1955-1969) result from a higher freq uency of large floods (> 20 year return period) and cool, wet climate under meridional circulation regimes. Phases of more moderate floods ( 5-20 year return period), corresponding to zonal circulation types (18 20-1874, 1920-1954), are characterized by enhanced lateral reworking a nd sediment transfer in upper reaches of the catchment, and channel na rrowing and infilling downstream. Rates of fluvial activity are reduce d in intermediate periods (1800-1819, 1985-1919) with no dominant circ ulation regime associated with lower flood frequency and magnitude. Th e results of this study provide a valuable guide for forecasting proba ble drainage basin and channel response to future climate change.