There has been considerable evidence that natural disasters can be threats to technological systems and when these threats are concomitant, they pose tremendous risks to countries and communities. Such risk (termed Natech risk) should be incorporated early in the design process, particularly in land-use planning of sites.In this study, a descriptive classification of Natech risk sources was developed, mainly from analysis of a Japanese database, to contribute to preliminary analysis of Natech risk. Analysis of the information gathered, resulted in a classification including fifteen physical effects and six physical impacts that cause technical disorder. Here, the pertinent aspects of natural hazards were termed physical effects, and the phenomena caused by physical effects were termed physical impacts: the primary observable consequences and influences on the functions of technological systems. The classification is expected to be helpful for Natech risk identification, by providing guidewords useful for risk assessment and management. (C) 2017 Elsevier Ltd. All rights reserved.