Collapsible dam and damming method

Claim 1

A collapsible dam structure for damming a watercourse, comprising: an outer inflatable envelope of a first inflated predetermined cross-sectional size mounted to extend across said watercourse, said outer envelope being operable when inflated to dam said watercourse, and having upstream and downstream portions relative to the longitudinal dimension of said watercourse; and at least one inner inflatable envelope mounted within said outer envelope, said inner envelope being of a second inflated predetermined cross-sectional size smaller than said first size and concentric therewith and having upstream and downstream portions and when inflated including an upstream portion in contact with and supporting said upstream portion of said outer envelope, fluid control means associated with said envelopes to independently inflate and deflate said envelopes to appropriate pressure levels within said envelopes dependent upon the exterior water pressure against said dam structure, each of said envelopes include upstream and downstream edges extending normal to the longitudinal dimension of said watercourse, and the upstream edges of said envelopes are mounted at substantially the same location in said watercourse, and the downstream edges of said envelopes spaced from said upstream edges are mounted in spaced apart locations one from the other along the longitudinal dimension of said watercourse and said edges are generally parallel one with the other.

Claim 4

A method of damming a waterhead, comprising: damming the waterhead with a first inflated envelope of a predetermined cross sectional size having an upstream portion facing said waterhead, and a downstream portion spaced therefrom, said first envelope having a firSt selected fluid pressure level therein; supporting at least a portion of the inside surface of said upstream portion of said first inflated envelope with a second inflated envelope mounted therein and concentric with said first envelope and having a predetermined cross-sectional size smaller than said first envelope, said second envelope having a second selected fluid pressure level therein higher than the pressure level of said first envelope.

Claim 5

A method of damming a waterhead, comprising: damming the waterhead with a first inflated envelope of a predetermined cross sectional size having an upstream portion facing said waterhead, and a downstream portion spaced therefrom, said first envelope having a firSt selected fluid pressure level therein; supporting at least a portion of the inside surface of said upstream portion of said first inflated envelope with a second inflated envelope mounted therein and concentric with said first envelope and having a predetermined cross-sectional size smaller than said first envelope, said second envelope having a second selected fluid pressure level therein higher than the pressure level of said first envelope.