Flash floods are hydrometeorological phenomena with often dramatic and catastrophic consequences from a material, human and environmental point of view. Often in the mountains, flash floods respond to heavy rainfall, concentrated in time and space, with a torrential character. These flash floods are a great challenge for the population and for managers. Their occurrence often poses problems for managers, especially in undeveloped basins. This contribution deals with the phenomenon of flash floods in an undeveloped mountain basin located in the Central High Atlas, which is known for its frequent occurrence of thunderstorms, especially during the summer and autumn. It covers an area of 578 km2, the perimeter is 124 km and the altitudes are between 760 and 3620 metres. A range of climatic and hydrological methodology is proposed with a statistical engine for the identification, extraction and analysis of flash floods. The main objective is to understand their hydrological behaviour, determine their mechanisms and their impacts on the environment.