PURPOSE: To arrange bottom laid panels by utilizing a supporting member so as to facilitate adjustment of horizontality and height of them, prevent generation of differential settlement so as to eliminate sedimentation of earth and sand, and easily remove earth and sand by flattening the upper face of the bottom laid panels even if earth and sand are sedimented thereon.

CONSTITUTION: In a fabricated waterway block constituted of U-shaped frames 2 to be installed at regular intervals along the lengthwise direction of a waterway, side wall panels set by being supported between the U-shaped frames 2 at their end parts, and bottom laid panels 1, a receiving part 6 of which both side parts are formed in parallel with each other is formed. A supporting member 4 for the bottom laid panel 1 of which the inside of both side parts are built up and bent so as to cover the U-shaped frame 2 is placed on the U-shaped frame 2, and the bottom laid panel 1 is arranged so as to engage with the receiving parts 6 of both side parts of the supporting member 4.