A note on the shapes of flexible dams

Flexible dams are in use as both temporary and permanent structures in a number of countries and consist of a flexible membrane secured to the channel bed. The membrane of the more common inflatable ones is secured at both ends and the dam inflated with air or water. Parachute dams in which the upper end of the membrane is fixed to a floating boom and restrained by guys are also discussed. The paper deals with the theoretical calculation of the shape of these dams when the retained water level is just at the crest of the dam, (i.e. with no overflow). In particular it deals with how the shape of a dam changes with increasing inflation and hence with the selection of the design parameters (the length of the membrane, the distance between the anchorages and inflation pressure) for a dam required for a given purpose.