The role of geomorphology in flood risk assessment

The most commonly used method of assessing flood risk is based on predicting the magnitude and extent of the ‘100-year’ or ‘200-year’ flood. Though potentially very useful to engineers, this information can mislead planners and developers into assuming that areas outside these limits are risk free. This paper reports on an alternative, geomorphological approach that has recently been examined in Wales to map the physical extent of the floodplain itself. Such mapping reflects actual evidence of fluvial activity rather than relying on modelled predictions and, therefore, is less likely to omit areas that could be at significant risk of flooding. It also provides a tool for investigating and predicting the response of river channels, floodplains and catchment hydrology to climate and land use changes over time.