a disposable net assembly is provided for a trap for collecting floatable debris in a waterway or combined sewer system . the net assembly includes a knitted bag - shaped mesh net having a frame surrounding the mouth of the net with the net secured around its rim to the frame . the net may be formed of an inner layer and an outer layer of mesh with the openings of the inner layer being substantially larger than the openings of the outer layer . the frame may be formed of a plastic molded material having side members tapered in the vertical direction to facilitate the changing of the netting assemblies and tapered in the downstream direction to lock into place under the force of the flow . several embodiments of the frame members have projections thereon which cooperate with a clamping element to hold the net to the frame . some embodiments of the members have parts that lock together with a post and hole construction while others employ a tension band to clamp the net to the projections on the frame . the net is preferably secured around its rim to the frame , with the mouth of the net extending around the outside and upstream side of the frame and over the surface having the projections . the net is preferably formed of a high strength and high stretch yarn , with rolled sewn seams and having reinforcing on the seams and on high stress areas of the net .