Stormy geomorphology: geomorphic contributions in an age of climate extremes

The increasing frequency and/or severity of extreme climate events are becoming increasingly apparent over multi-decadal timescales at the global scale, albeit with relatively low scientific confidence. At the regional scale, scientific confidence in the future trends of extreme event likelihood is stronger, although the trends are spatially variable. Confidence in these extreme climate risks is muddied by the confounding effects of internal landscape system dynamics and external forcing factors such as changes in land use and river and coastal engineering. Geomorphology is a critical discipline in disentangling climate change impacts from other controlling factors, thereby contributing to debates over societal adaptation to extreme events. We review four main geomorphic contributions to flood and storm science. First, we show how palaeogeomorphological and current process studies can extend the historical flood record while also unraveling the complex interactions between internal geomorphic dynamics, human impacts and changes in climate regimes. A key outcome will be improved quantification of flood probabilities and the hazard dimension of flood risk. Second, we present evidence showing how antecedent geomorphological and climate parameters can alter the risk and magnitude of landscape change caused by extreme events. Third, we show that geomorphic processes can both mediate and increase the geomorphological impacts of extreme events, influencing societal risk. Fourthly, we show the potential of managing flood and storm risk through the geomorphic system, both near-term (next 50years) and longer-term. We recommend that key methods of managing flooding and erosion will be more effective if risk assessments include palaeodata, if geomorphological science is used to underpin nature-based management approaches, and if land-use management addresses changes in geomorphic process regimes that extreme events can trigger. We argue that adopting geomorphologically-grounded adaptation strategies will enable society to develop more resilient, less vulnerable socio-geomorphological systems fit for an age of climate extremes. (c) 2016 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.