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 Trenches provide excellent exposures of sediments and deformation structures concealed beneath the surface at key sites. The study of the trench walls (e.g. logging, retrodeformation analysis) together with geochronological data allows to obtain a great deal of objective and quantitative information for geomorphological, paleoenvironmental and geohazard investigations. The trenching technique has been mainly developed in the field of Paleoseismology for assessing the seismogenic potential of active faults. However, recent investigations illustrate its practicality for analyzing other hazardous processes (landslides, sacking, sinkholes, earth fissures), the inferring evolution of geomorphic systems and reconstructing paleoenvironmental changes. The talk presents the main methodological aspects of the technique and illustrates some examples of its application, including case studies from Saudi Arabia.