Floodplains may be transformed when environmental changes or human activity causes alluvial systems to cross channel pattern thresholds. Thresholds between pattern states based on occurrence fields are only available for some pattern distinctions, and these may not encompass the alluvial contexts and range of dynamic factors involved. Pattern changes now known from the UK Holocene are reviewed as a basis for appreciating the potential for future transformations in a changing environment. These involved episodic boulder and gravel spreads in upland environments, and braiding meandering, anastomosing → meandering and active inactive transformations in more lowland contexts. Concern for possible impacts of climatic change need to be grounded in an appreciation of the nature and scale of these past changes. Some potential future changes may be relatively predictable in location (braiding meandering); others are more difficult given both present knowledge and the varying, modified and inheritance-rich ‘contexts of vulnerability’ that floodplains now represent. Implications for management are discussed. Copyright © 2010 John Wiley & Sons, Ltd.