A liner assembly (322) for a sand trap (10) includes a retainer layer (329) that is positioned between a base (18) of the sand trap (10) and a filling material (16) within a cavity (13) of the sand trap (10). The retainer layer (329) is covered by the filling material (16) so that the retainer layer (329) is substantially unexposed. The retainer layer (329) includes a plurality of spaced apart projections (330) that can be formed from plastic, such as synthetic turf material. In certain embodiments, the filling material (16) fills the spaces between the projections (330). The retainer layer (329) can be substantially water impermeable and can cover at least approximately a majority of the surface area of the cavity (13). The retainer layer (329) can be positioned within the cavity at an angle (328) that is at least 10 degrees relative to the horizontal (300).