Our intention is to highlight the unacknowledged and sometimes fatal hazard of rapid rate of rise in river level and flow. Using the full 15 min records of 260 Scottish gauging stations, we have extracted the maximum rates of 15 min rise in events generated by intense convective rainfall and described their characteristics in terms of the severity of the hazard within and between catchments. Events have all the properties of kinematic shock whose mere existence has previously been doubted.