Patent Publication Number: US-2002012571-A1

Title: Sediment trap

Description:
[0001] This application claims priority to provisional patent application Serial No. 60/218,758 filed on Jul. 17, 2000. 
    
    
     
       FIELD OF THE INVENTION  
       [0002] This invention relates generally to the prevention of sediment movement in water and more particularly to a system and method for trapping sediment in flowing water such as rivers and ditches.  
       BACKGROUND OF THE INVENTION  
       [0003] Water in rivers and ditches accumulates sediment and other particles as it moves. The sediment particles are carried by the water until they fall out due to gravity or by impact with a barrier, filter or other impediment. Over time, a significant build-up of sediment can occur in certain locations or across an area, potentially leading to blockage of the waterway, faster water flow in a restricted area and/or erosion as the water seeks an alternate route.  
       [0004] Prior attempts to prevent and minimize sediment build-up have involved merely removing the sediment or installing blockages or filters in the waterway, such as breakwater devices or dams. Many of these devices are designed to directly reflect waves and water movement and further agitate the water without allowing sediment to precipitate. If such a breakwater or dam extends above the waterline, it prevents all water flow and prevents all objects from flowing with the water, including boats and fish. Alternately, breakwaters below the waterline allow a limited flow and limited navigation, but over time become ineffective due to accumulated debris.  
       [0005] When such devices lower the amount of water flowing, the backpressure diverts the water to erode an alternate channel in an attempt to resume the interrupted flow. Further, such devices need periodic dredging of the surrounding debris and/or removal or replacement due to sediment build-up.  
       [0006] There is a need for a device in moving water which minimizes sediment movement and erosion with a minimum of maintenance. The present invention addresses these concerns.  
       SUMMARY  
       [0007] A preferred embodiment of the present invention provides a sediment trap for the floor of a waterway, such as a ditch or river, where water moves downstream. In a preferred embodiment the trap forms a “still water” layer in the waterway wherein the movement of a layer of water substantially corresponding in depth to the height of the trap is slowed and/or stopped, allowing sediment to precipitate. Preferably the trap then gentles the water flow to minimize the accumulation of additional sediment.  
       [0008] In a preferred embodiment, the trap includes a vertical wall mountable to the floor of the waterway having a top edge and a height less than the depth of the water. The trap includes means attachable to the vertical wall for fixing the trap in place on the floor of the waterway. In one preferred embodiment, the sediment trap further includes a ramp portion having a length extending downstream from the top edge of the vertical wall downwardly toward the floor of the waterway. Preferably the ratio of the height of the vertical wall to the length of the ramp portion is between approximately 1:4 and approximately 1:8. More preferably, the height of the vertical wall is approximately one foot. The sediment trap may include an anchoring weight mounted to the vertical wall and the ramp portion.  
       [0009] In an alternate preferred embodiment, the trap includes a vertical wall portion made from a resiliently yielding material such as rubber sheet, plastic sheeting or a reinforced fabric weave. The material has sufficient rigidity to impede the flow of water for its vertical height, but yields when struck by a solid object such as a boat or propeller.  
       [0010] It is a preferred object of the present invention to provide an improved sediment trap for waterways such as rivers and ditches.  
       [0011] It is a further preferred object of the present invention to provides an improved apparatus and method for creating a layer of still water in a flowing waterway to allow sediment to precipitate and to minimize the accumulation of further sediment.  
       [0012] Further objects, features and advantages of the present invention shall become apparent from the detailed drawings and descriptions provided herein.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0013]FIG. 1 is a perspective illustration of one embodiment of the current invention.  
     [0014]FIG. 2 is a side view of the embodiment of FIG. 1  
     [0015]FIG. 3 is a perspective illustration of an alternate embodiment of the current invention.  
     [0016]FIG. 4 is a perspective illustration of a further alternate embodiment similar to the embodiment of FIG. 3.  
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0017] For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations, modifications, and further applications of the principles of the invention being contemplated as would normally occur to one skilled in the art to which the invention relates.  
     [0018] The present invention uses the principle of “still water” to minimize the movement of sediment in flowing water. With “still water” a sediment trap is installed on the bottom of a water channel or waterway and extends vertically a distance for a portion of the water&#39;s depth, such as approximately one foot above the channel&#39;s floor. The trap substantially stops the flow of water in a lower layer of the channel extending before the trap while allowing the remaining water in an upper layer to flow over the trap. This non-flowing bottom portion of “still water” allows the sediment to settle out before reaching the trap. Additionally in one embodiment, the flowing water flows past the vertical portion and continues along a descending ramp or slope. This descending slope imparts a gentle flow to the water minimizing water agitation over the trap, and substantially lowers the pick-up of additional sediment.  
     [0019] The sediment traps of the present invention allow water to flow over the trap, but substantially prevents sediment accumulation. Additionally, fish and boats can travel the waterway without being blocked. The traps are below the surface of the water with a minimal height, so they are minimally noticeable. The embodiment of FIGS. 1 and 2 is preferably used in waterways, such as ditches, which are greater than one foot in depth, but are not navigated by boats. Alternately, the illustrated embodiment may be used in navigable waterways where the water has sufficient depth that typical boat drafts have sufficient clearance above the traps.  
     [0020] The structure for one embodiment of the present invention is illustrated in FIGS. 1 and 2. FIG. 1 shows installation  11  of sediment trap  10  in a water channel such as a ditch. Sediment trap  10  has a vertical wall or panel  12  at its upstream side which extends above the channel floor a vertical height  25 . Vertical height  25  is preferably less than the depth of the water channel. In a preferred embodiment, vertical wall  12  has a height  25  of approximately one foot.  
     [0021] In this preferred embodiment, where vertical wall  12  has a height  25  of approximately one foot, the water depth is independent of the wall height so long as it is greater than one foot. Preferably sediment trap  10  functions to block or impede water flow in the lower or bottom layer of water in the water channel. A depth of one foot has been found to be a preferred depth for this lower layer. The upper layer of water above the lower layer continues to flow unimpeded over trap  10 . The depth of the upper layer of water may vary.  
     [0022] In one preferred embodiment, a downward sloping panel or ramp  14  extends at an angle downstream from the top edge of vertical wall  12  towards the floor of the water channel. Preferably, sloping panel  14  extends at least four feet and more preferably is between about four and about eight feet in length. This forms a rise versus run ratio between approximately 1:4 and 1:8. A third panel or floor  16  may optionally be used to increase the stability of trap  10  by connecting the downstream end of panel  14  to the foot of vertical wall  12 . The height  25  of vertical wall  12  and length of panel  14  may be varied, preferably maintaining a ratio of height to ramp length of between approximately 1:4 and 1:8.  
     [0023] Trap  10  may be anchored in place with pipes or stakes  20  which extend into the channel floor and which are attached to trap  10  using standard means such as clamps, eyebolts or bolts. Alternately, stakes  20  may be received through holes in trap  10  or connected with other connection methods such as welding. Trap  10  preferably has sufficient width to extend across the width of the watercourse or multiple traps may be arranged in a horizontal line to extend across a watercourse. This may be done with one piece, or multiple sections placed side by side. For convenience, a width of eight feet or less per trap is preferred. The embodiment of trap  10  illustrated in FIGS.  1 - 2  is preferred for non-navigated waterways such as ditches.  
     [0024] Anchoring weight  30  such as sand, gravel, stones or concrete can be added and/or attached to the inside of trap  10  and optionally sealed inside. Panels  12 ,  14  and  16  can be connected by standard means such as welding, bending, bolted via flanges or brackets. Preferably, trap  10  is made from stainless steel, heavy duty plastic or a similar material with sufficient strength and durability when placed in a watercourse.  
     [0025] An alternate embodiment of the present invention is illustrated in FIGS.  3 - 4 . In the embodiment of FIG. 3, sediment trap  100  includes a vertical portion  112  held in place by two base plates  116 . In one preferred embodiment, vertical portion  112  has a height of approximately one-foot. A variation of this embodiment shown in FIG. 4 illustrates one base plate  116 ′ and brackets  117  to hold vertical portion  112 . Base plates  116  or  116 ′ are anchored to the water channel floor with durable connectors, such as stakes or pipes  120 .  
     [0026] Vertical portion  112  is formed from a rigid but resilient material and may be reinforced with splines  118 . In one preferred embodiment, vertical portion  112  is made from a {fraction (7/16)}″ to ½″ thick belting or material such as a rubber sheet, plastic sheeting or a reinforced fabric weave. Vertical portion  112  preferably has sufficient rigidity to inhibit the flow of water for its vertical height, but is resiliently yielding if struck by a boat or propeller. The embodiment of trap  100  is preferred for navigable waterways such as rivers.  
     [0027] In use, sediment traps  10  or  100  may be made in various widths, but preferably are made in eight foot sections for convenience. For installation, one or more trap sections are lined across the width of a water channel end-to-end, and extensions  50  of plating or a similar barrier extends from each end section towards and preferable the channel banks to prevent water from going around the traps and eroding the sides of the waterway. Once in place, the trap sections are preferably fixed in place with stakes  20 , internal weight  30  or similar means to prevent movement.  
     [0028] Once deployed, the vertical wall of the trap causes a “still water” layer in the area approaching the trap up to the height of the trap. The still water area either does not move or has a slower flow, with the remainder of the water passing as a layer above the still portion. The still water area extends upstream of the trap, and particularly on level terrain can extend a considerable distance.  
     [0029] If the water channel has a significant elevation change, preferably multiple tiers of traps are installed in the water channel, in a stepped or terraced manner. Preferably one tier is installed per change in elevation corresponding to vertical height  25 . In a preferred embodiment, one trap tier with a one foot vertical height is installed for every one foot drop in elevation. This allows a corresponding terracing of the still water areas. Each still water area allows sediment to be deposited by the water and insulates the flowing upper layer of water from accumulating sediment in the still water area.  
     [0030] The remaining water flows over the trap and the sloping ramp portion of the trap. The relatively long sloping of the trap after the vertical portion functions to gentle the water flow by reducing turbulence, agitation and cavitation in the water to minimize disruption in the water flow and to minimize the accumulation of new sediment or particle materials.  
     [0031] While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.