This paper deals with some aspects of the design procedure to be followed in designing an overflow dam on alluvial foundation material, such as is encountered in the lower reaches of some South African rivers. Several dams built on river sand have been in successful operation in Wisconsin. Construction and, in some cases, alterations after construction, was based on an extensive programme of model analysis, not usually within the means of every design engineer. This paper draws from these experiments and recommendations for design data. The application of the design assumptions to the design and stability analysis of a worked out example, is an independent undertaking, serving to illustrate and qualify the major stability considerations to be provided for.