The introductory chapter deals with the concept of palaeochannels and water resource management, outlining its historical background and its linkage throughout the world. It evaluates the changes in hydrological extremes caused by climate change. The various spatial scale and temporal scales at which the previous studies have been carried out are discussed. Moreover, the present condition of hydrological extremes, i.e. flood and drought of the Bengal Delta, is focused. The quantitative and qualitative conditions of water resources in the study area are analysed. Finally, this chapter intends to portray the necessity of carrying out this piece of work in the context of the need of palaeochannels in sustainable water resource management.