To provide a water cutoff vegetative base material which is useful in general civil engineering works such as a slope, a slope top, and a revetment section, in a waste disposal area as a water cutoff sheet forming a bottom surface and a slope of the waste disposal area, and as a water cutoff capping sheet for preventing movement of harmful substance due to rainwater infiltration after completion of landfill, etc.

The water cutoff vegetative base material (12) is formed of a water cutoff sheet (9), and three-dimensional network bodies (3) laminated on and connected to both surfaces of the same in one body. Each network body is made of a thermoplastic resin, and formed by irregularly superposing a plurality of continuous fibers having a diameter of 0.1 to 2 mm, on each other in a longitudinal direction. One of three-dimensional network body layers has a function (cover soil retaining layer 3a) of preventing cover soil from deviating, and the other three-dimensional network body layer has a function (slip preventive layer 3b) of preventing the water cutoff sheet from slipping down.