The book describes flash floods - one of the most devastating of natural hazards, which develop in a period of minutes to a few hours. Floods of this type are often characterised by fast flowing deep water and a high debris content which - combined with the short lead time available for warnings - add to the risk to people and property. The main cause of flash flooding is usually heavy rainfall; other causes can include the break- up of ice jams, dam breaches, and the failure of flood defenses and levees.The volume discusses the increasing use of meteorological observation and forecasting techniques to extend the lead time available for warning, combined with hydrological models for the river response. It also presents probabilistic techniques and some current areas of research which include the use of weather radar and satellite data in improving meteorological forecasts, the development of improved forecasting and observation techniques for mountainous regions, and the use of distributed hydrological models specifically adapted for flash flood modelling.This book reviews recent developments in this active research area, with a focus on events caused by heavy rainfall (including debris flows and landslides), but also considering other types of flash flooding, such as that caused by ice jams and dam and levee breaches. The topics covered include meteorological forecasting and monitoring techniques, rainfall-runoff and river modelling, approaches to issuing flood warnings, and some of the societal and behavioural aspects of providing an effective emergency response. A number of international examples of the application of these techniques are also provided.The book is potentially useful on civil engineering, water resources, meteorology and hydrology courses (and for post graduate studies) but is primarily intended as a review of the topic for a wider audience.