Episodically volatile high energy non-cohesive river-floodplain systems: New information from the Ping River, Thailand, and a global review

Volatile rivers that involve floodplain stripping and subsequent floodplain reconstruction by vertical accretion are poorly known worldwide. This paper aims to partially fill this knowledge gap by a review of existing information and the provision of the currently most detailed account of such a river, namely the Ping River of northern Thailand. Recognition of this river type depends upon stratigraphic and morphostratigraphic analysis and so does not come within the ambit of those who focus only on river form and modern flood hydrology, and also not within the ambit of ‘traditional’ palaeoflood hydrology. A morphostratigraphic analysis of the Ping River adds to the small but valuable corpus of existing studies and provides an indication of the level of detail that is required for an in-depth understanding. A global review shows that extreme rainfall is always involved in floodplain stripping, although the sensitivity to rainfall extremes of catchments is not understood, including the contributions of land use, topography and alluvial resistance to erosion. The Ping River has the same characteristics as other volatile rivers, with an average interarrival time for stripping events of about three centuries probably caused by different combinations of wet periods, tropical lows, typhoons, and atmospheric rivers. As the intensity of extreme rainfall increases as Earth warms, the frequency of floodplain stripping events may increase with implications for both the pace of change in some fluvial landscapes and flood mitigation strategies.