fig1 illustrates the basic components of one system 10 of the prior art described in the background of the invention above . the system 10 includes one or more traps 12 , illustrated as two in number , separately designated as traps 12 a and 12 b . the traps 12 a , 12 b are located within a flow constraining housing or enclosure 11 between inlet 13 and outlet 14 thereof . the inlet 13 and the outlet 14 are each respectively connected in a known manner to conduits 15 and 16 , which may be storm drain or combined sewer conduits or other structures or the terrain of the site . the traps 12 a , 12 b each include a netting assembly 19 formed of a bag - shaped mesh net 17 that is attached to a lifting basket 18 . each of the netting assemblies 19 captures and holds floatable velocity borne debris 20 entering enclosure 11 through inlet 13 . the arrows 25 indicate the direction of water flow . perforations or openings in nets 17 may vary in size depending on the intended use , with sizes generally in the range of from about 0 . 1 ″ to about 2 ″. nets 17 are open on the upstream facing end 17 a thereof , toward inlet 13 of enclosure 11 . upper support members ( not shown in fig1 ) are attached to lifting baskets 18 for allowing the netting assemblies 19 of traps 12 a , 12 b to be lifted out of enclosure 11 for periodic removal of captured debris . the netting assemblies 19 are configured such that the nets 17 provide a large filter area for the size of the mouth , thereby minimizing head loss . for example , 80 square feet of net 17 may be provided for a netting assembly mouth area of 6½ square feet , resulting in a pressure drop across a net 17 of three or four pounds . a bypass weir ( not shown in fig1 ) or screen is typically located upstream of traps 12 and on one side of inlet 13 to permit continued flow in the event that the nets 17 of traps 12 a , 12 b are filled to capacity with debris . to signal that nets 17 of the netting assemblies 19 of traps 12 a , 12 b are in need of replacement or emptying , sensing and signaling mechanisms may be provided . the multiple trap system 10 can be configured to provide continuous and uninterrupted capture of debris through second trap 12 b after the netting assembly of first trap 12 a has been filled and during the process of removing and replacing it . while servicing is being performed , movable panels can be positioned in front of each respective trap 12 a or 12 b being serviced , as necessary , prior to its removal from enclosure 11 . in this way , the system 10 is protected against passage of floatable debris during net removal and replacement . fig1 a - 1c illustrate the basic system 10 of the prior art in three environments . these arrangements are generally described in a publication of the united states environmental protection agency , office of water , no . epa 832 - f - 99 - 037 , september , 1999 , hereby expressly incorporated by reference herein . in particular , in fig1 a , an in - line system 10 a is illustrated in which the two traps 12 a , 12 b are contained in an enclosure in the form of an underground or subterranean vault 11 a . the vault 11 a includes its inlet 13 a and its outlet 14 a respectively connected to conduits in the form of buried pipes 15 a , 16 a , for example , of a storm drain . the in - line traps 12 a , 12 b each include a netting assembly 19 with a mesh net 17 installed in and held in place by a respective lifting basket 18 . a lifting bridle ( not shown ) is attached to upper support members 21 of the lifting basket 18 for allowing the netting assemblies 19 of traps 12 a and 12 b to be lifted out of vault 11 a through doors 22 a for periodic removal of captured debris . a bypass screen 23 a is located above the traps 12 a , 12 b to allow flow to divert from the inlet 13 a to permit continued flow in the event that nets 17 of the traps 12 a , 12 b are both filled to capacity with debris . in fig1 b , a floating system 10 b is illustrated that is configured to float in a body of water in front of a stream , pipe or other water source from which enters into the body of water a flow of water containing trash or floatables to be removed by the system . the direction of water flow into and through the system 10 b is also indicated by arrows 19 . the floating system 10 b also includes two traps 12 a , 12 b , shown in a floating hull 11 b that is provided with closed cell foam panels 23 and pontoons to float the hull at the surface 28 of the body of water . the traps 12 a , 12 b also each include a mesh net 17 held in place within a lifting support 18 a . because the system 10 b is floating and the traps 12 a , 12 b are immersed in water , a less extensive support frame 18 a is substituted for the lifting basket 18 of system 10 a , described above . in the system 10 b , the hull 11 b has its inlet 13 b extending above and below the surface 28 of the water so that trash or floatables at and immediately below the surface enter through it into the interior of the hull 11 b . the hull 11 b has its outlet 14 b below the water surface 28 on the back of the hull 11 b . the inlet conduit 15 is formed of a set of curtains 15 b which hang from below the inlet 13 b and from floats 24 extending respectively between the hull 11 b on both sides of the inlet 13 b to the shore on the opposite sides of the flowing source , connected to buried concrete conduits ( not shown ) of a storm drain , for example . the curtains 15 b may extend from the water surface 28 to the bottom 29 of the water body and channel water from the source into the inlet 13 b . the traps 12 a , 12 b are supported in the hull 11 b in a manner similar to the way they are supported in the vault 11 a described above . they can be lifted out of hull 11 b through grate doors 22 b for periodic removal of captured debris from the nets 17 thereof . in fig1 c , an end - of - pipe system 10 c is illustrated in which the two traps 12 a , 12 b are shown in an enclosure in the form of a surface mounted three - sided concrete headwall and knee wall enclosed cavity 11 c having an open end that defines its outlet 14 c . the cavity 11 c has its inlet 13 c connected to a pipe 15 c draining into the cavity 11 c . the traps 12 a , 12 b each include a net assembly 19 having a mesh net 17 . a fiberglass drain grating 16 c is provided beneath the netting assemblies 19 to allow flow to exit each net 17 through its bottom to the outlet 14 c of the enclosure 11 c . the net 17 of each netting assembly is attached to a lifting structure ( not shown ), which may be similar to the lifting basket 18 described in fig1 a above , or in the form of lifting frame 18 a described in fig1 b above where the traps 12 a , 12 b are submerged . door grates 22 c are provided above the traps 12 a , 12 b to permit them to be raised for periodic removal of captured debris . a bypass weir 23 c may be located above the traps 12 a , 12 b to allow flow to divert from the inlet 13 to permit continued flow in the event that traps 12 a , 12 b are both filled to capacity with debris . in fig2 , 2 a and 2 b are illustrated netting assemblies for the traps 12 for use in systems 10 of the various types illustrated in fig1 a - 1c described above . according to certain aspects of the invention , the netting assemblies 19 are constructed with a mesh net 17 connected to a frame assembly 30 . the frame assembly 30 includes a rectangular frame body having a pair of horizontal top and bottom members 31 and 32 , respectively , and a pair of side members 33 . the top member 31 is wider than the bottom member 32 , and the side members 33 are tapered from the wider top member toward the narrower bottom member 32 , as illustrated in fig2 b , for easy installation and removal from the lifting basket 18 or support frame 18 a . the side members 33 are also inwardly tapered in the downstream direction , as illustrated in fig2 a , to lock into the supporting rails as the flow goes through the nets 17 . flow direction is indicated by the arrows 25 . each of the members 31 - 33 has a rim 34 on the upstream side thereof and a recessed step 35 on the downstream side thereof . a pattern of holes 36 is formed in the steps 35 of each of the members 31 - 33 . each of the members 31 - 33 has associated therewith a plate 37 having a plurality of projections in the form of posts 38 arranged in a pattern that corresponds to the pattern of the holes 36 in the respectively associated member 31 - 33 of the frame 30 so that the plates 37 can be connected to the members 31 - 33 by snap fitting the posts 38 into the holes 36 . the plates 37 are so connected with the edge of the mouth of the net 17 between the plate 37 and the respective member 31 - 33 and the posts 38 extending through holes in the mesh of the net 17 , thereby locking the mouth of the net 17 to the frame 30 . when so connected , the plates 37 set into the steps 35 so that the tops thereof are flush with the lip 34 of the members 31 - 33 . when the net 17 is attached to the frame 30 , the net extends around the outside of the members 31 - 33 with the mouth of the net wrapping around the upstream side of the frame 30 to the inside of the frame 30 and between the plates 37 and the members 31 - 33 . the frame 30 may be made of wood and the plates 37 made of metal , but other materials may be used . in one preferred embodiment , the frame 30 is formed of an integral piece of molded plastic material . the plates 37 may also be formed of molded plastic . the frame 30 securely attaches to the nets 17 by being formed of elements that clamp together with the mesh material of the nets 17 between them , with one of the elements having posts or projections thereon against which the other member bears so that the projections serve as hooks that trap the net between the elements while the other element prevents the net from slipping off the projections . an alternative frame structure 18 is illustrated in fig3 , 3 a , 3 b and 3 c , in which mesh net 17 is shown connected to a frame assembly 40 . the frame assembly 40 is a two part rectangular frame that includes an inner frame portion 40 a having an array of holes 46 on the upstream facing side thereof and an outer frame portion 40 b having a matching array of posts on the downstream facing side thereof . the two portions 40 a , 40 b of the frame snap together and clamp the mouth of the net 17 therebetween . the two parts of the frame 40 are preferably formed of an integral piece of molded plastic , but other materials may be used . the frame 40 has a pair of horizontal top and bottom members 41 and 42 and a pair of side members 43 . the side members are tapered inwardly in the downstream direction and fit in correspondingly tapered vertical channels 44 in vertical rails 45 that are part of the lifting basket 18 or support frame 18 a . further , the top member 41 is thicker in the flow direction ( that is , upstream to downstream ) than is the bottom member 42 ; and the side members 43 are correspondingly tapered in the downward direction to fit into the channels 44 , which are similarly tapered , as illustrated in fig3 a . as a result of the tapers , the frame 40 of the netting assemblies 19 fit firmly in the channels 44 of the rails 45 when in position , but can be loosened by impact and removed with a minimum of sliding friction . fig3 b shows the net 17 wrapped around the outside of the frame 40 with the mouth of the net 17 wrapping around the front of the frame 40 and extending between the portions 40 a , 40 b thereof from the inside . alternatively , fig3 c shows the net 17 wrapped around the inside of the frame 40 with the mouth of the net 17 wrapping around the front of the frame 40 and extending between the portions 40 a , 40 b thereof from the outside . as a result of the tapers described above , the greater the forces on the traps , the more tightly the mesh nets 17 are gripped and the less likely are the nets to pull out or tear around the posts . fig4 a illustrates a two layered net 17 that includes an inner net 17 a of a course mesh having holes mounted to frame structure 18 c so as to extend through the inside of the frame and with an outer net 17 b of a fine mesh mounted to frame structure 18 c so as to extend around the outside of the frame and thereby enclosing the inner net . the holes in the inner net 17 a may , for example , be about 1 - 2 inches in size with the holes in the outer net 17 b being of about ½ inches in size . the holes of the inner net 17 a should be at least two to three times larger on a side than those of the outer net , with a cross sectional area of at least about four times the area of the holes of the outer net . as a result , large pieces of debris 48 such as plastic bottles , cans , plastic bags , styrofoam cups , etc . only are trapped by the inner net 17 a while smaller pieces of debris 49 pass through the larger holes of the inner net 17 a and are trapped by the outer net 17 b . fig5 , 5 a and 5 b illustrate netting assemblies for the traps 12 that are alternative embodiments of the assemblies of fig2 - 2b and fig3 - 3c described above . in fig5 - 5b , the traps 12 are each constructed with mesh net 17 connected to a frame assembly 50 . the frame assembly 50 includes a rectangular frame body . as with the embodiments above , the frame 50 is preferably formed of an integral piece of molded plastic , but other materials are suitable . the body of frame 50 has a pair of horizontal top and bottom members 51 and 52 , respectively , and a pair of side members 53 , with the top member 51 wider than the bottom member 52 and the side members 53 tapered from top to bottom as was illustrated in the embodiment of fig2 b . the side members 53 are also inwardly tapered in the downstream direction , as illustrated in fig5 a . each of the members 51 - 53 has an outside surface 54 having a groove 55 extending around the frame 50 . on the bottom surface of the groove 55 is preferably a plurality of projections or posts 56 to help grasp the netting material , particularly where the frame is formed of plastic or other low friction material . a clamping element in the form of a tension band 57 lies in the groove 55 in contact with the tips of the projections 56 . the tension band may be of a natural fiber , metal or plastic . plastic is particularly suitable for the band 57 . the net 17 extends between the band 57 and the frame members 51 - 53 , so that the mouth of the net 17 is locked to the frame 50 . when the frame 50 is inserted into the rails of the system , the tapered frame is forced against the frame by the forces produced by the flowing water on the net 17 to further clamp the net 17 between the frame 50 and the rail . other applications of the invention can be made . those skilled in the art will appreciate that the applications of the present invention herein are varied , and that the invention is described in preferred embodiments . accordingly , additions and modifications can be made without departing from the principles of the invention . accordingly , the following is claimed ;