This volume synthesizes and analyzes thirty years of hydrological research in the Danum Valley Conservation Area, a lowland dipterocarp rainforest in Sabah, Malaysia.  Ian Douglas explores the role of water in the rainforest ecosystem, setting out the ecological, climatological and geological context of present-day hydrological processes, soil erosion and stream sedimentation. He emphasizes the role of extreme events and natural disturbances in sediment supplies and the evolution of drainage pathways and explains the pathways of rainfall and stream sediment. Douglas then explores the impacts caused by logging, the extreme pulses of sedimentation and the effects of log removal and logging road construction, examining the effects of major storms in the 20 years after tree harvesting. Methods of minimizing logging damage to soils and streams are discussed and the effects on flora and fauns are considered.