A series of quasi-quantitative experiments on delta building were carried out in a laboratory flume for the purpose of studying the mechanics of deposition of topsets, foresets, and bottomsets. The genesis of these sets can be rationally explained through the discipline of sediment transport mechanics by taking cognizance of (a) the hydraulic phenomena of gradually varied and rapidly varied flow, (6) the concept of aggradation to a profile of equilibrium. The geometry of a delta front is controlled by the dynamics of the environment of deposition, and the frontal profile can be inter- preted as a function of the micro-mechanics of particle movement in the transition zone where the stream enters the basin of deposition.