Abstract:
A method of forming a maintenance free channel is disclosed. The method consists of positioning a plurality of curtain devices along a desired path in a waterway. The curtain devices each consists of an elongated float and an elongated flexible curtain depending from a first side of the elongated float. The elongated curtain has a bottom end with a weight extending along the entire length of the elongated float. The elongated float is configured to be sufficiently buoyant to support the curtain in an upward direction. The length of the elongated float is selected to equal a desired length of the channel. The height of the elongated flexible curtain is selected to be approximately equal to the depth of the waterway such that the elongated weight remains on the bottom while the elongated cylindrical float remains on the surface.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates generally to devices and methods for keeping water channels clear of silt so as to remain navigable. 
       BACKGROUND OF THE INVENTION 
       [0002]    Waterways in rivers or other bodies of water often contain natural channels whose depth is sufficient for safe navigation. Over time, however, natural channels tend to accumulate silt on their bottoms, thereby reducing their depth. Given enough time, river action, tidal action and weather conditions, a channel can become so silted as to render it unfit for navigation. In order to keep channels navigable, dredging is used to reduce the amount of silt on the bottom of the channel. However, do to the action of water currents, dredging requires that a wider area of the channel must be dredged to be effective. As a result, even if the desired channel is only 10 or 20 meters wide, a path 30 meters or more wide would need to be dredged to ensure that the central 10 or 20 meters is clear. In many cases, water currents and tidal action cause the rapid accumulation of silt, necessitating almost annual dredging of the channel. Building walls around the channel would be too expensive, and would likely fail due to hydro-dynamic forces. Therefore, a less expensive and simple method of keeping navigation channels free from silt is required. 
       SUMMARY OF THE INVENTION 
       [0003]    In accordance with one aspect of the present invention, there is provided a method of forming a channel in a waterway having a surface, a depth and a bottom. The channel formed will be self cleaning and not require dredging. The method consists of the steps of providing a fixed channel curtain device and positioning said fixed channel curtain device along a desired path in the waterway. The fixed channel curtain device consists of an elongated cylindrical float having a length and a first side. An elongated flexible curtain depends from the first side of the elongated cylindrical float and extends along the entire length of the elongated cylindrical float. The elongated curtain has a bottom end opposite where the elongated curtain depends from the elongated cylindrical float. An elongated weight is formed on the bottom end of the elongated flexible curtain, the elongated weight extending along the entire length of the elongated cylindrical float. The elongated cylindrical float is configured to be sufficiently buoyant to float the device. The length of the elongated float is selected to equal a desired length of the channel. The height of the elongated flexible curtain is selected to be approximately equal to the depth of the waterway such that the elongated weight remains on the bottom while the elongated cylindrical float remains on the surface. 
         [0004]    With the foregoing in view, and other advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, the invention is herein described by reference to the accompanying drawings forming a part hereof, which includes a description of the preferred typical embodiment of the principles of the present invention. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a cross sectional view of a channel constructed using the method of the present invention. 
           [0006]      FIG. 2  is a schematic view of channels constructed using the method of the present invention charted on a geographic map of a water way. 
           [0007]      FIG. 3  is a cross sectional view of a curtain device made in accordance with the present invention. 
       
    
    
       [0008]    In the drawings like characters of reference indicate corresponding parts in the different figures. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0009]    Referring firstly to  FIGS. 1 , the present invention is a method and device for forming navigation channels in a waterway. The invention, shown generally as item  10 , consists of a pair of fixed channel curtain devices  18  and  18   a  which are strategically placed in waterway  12 . Water way  12  consists of any potentially navigable waterway having a bottom  14  and a surface  16  with a depth between the bottom and surface of sufficient dimension to permit the passage of water vehicles. Fixed channel curtain devices  18  and  18   a  are placed along waterway  12  parallel to each other to form navigation channel  15 . The width of channel  15  is determined by the distance separating curtain devices  18  and  18   a.  Channel curtain devices  18  and  18   a  are identical and each consists of an elongated cylindrical float  20  and  20   a,  respectively, to which a flexible curtain  22  and  22   a  is attached, respectively. Curtains  22  and  22   a  depend from an attachment point  24 ,  24   a  positioned on one side of floats  20 ,  20   a,  respectively. A lower end  30 ,  30   a  is formed on curtains  22  and  22   a,  respectively, to which an elongated weight  32 ,  32   a  is attached. 
         [0010]    Curtain  22 ,  22   a  and weights  32 ,  32   a  extend the entire length of elongated floats  20 ,  20   a , respectively. Ballast weights  26  and  26   a  are formed on floats  18 ,  18   a,  opposite attachment points  24 ,  24   a,  respectively. Ballast weights  26  and  26   a  are sufficiently heavy so that when floats  18 ,  18   a  are floated on water surface  16 , the ballast weights will tend to rotate the floats so that the ballast weights are oriented downward, as illustrated with device  18   a.    
         [0011]    Elongated cylindrical floats  20  and  20   a  preferably consist of elongated cylinders of expanded polyethylene, as is used in the construction of “pool noodles”. Elongated floats  20  and  20   a  are made as long as may be required (several meters) to be used in the building of navigable channels. Flexible curtains  22  and  22   a  are preferably made from an artificial fabric material which is inexpensive, strong and resistant to rotting and decay. The fabric need not be waterproof, but it should be a relatively tight fabric capable of resisting the flow of water through the fabric. Several non-woven fabrics commonly used in construction and landscaping applications can be utilized. 
         [0012]    Weights  32  and  32   a  are formed on bottom ends  30  and  30   a  of curtains  22  and  22   a  by means known generally in the art. As best seen in  FIG. 3 , preferably an elongated pocket  40  is formed on the bottom end of the fabric curtain  22  and the elongated weights is inserted therein. Pocket  40  can be formed by sewing or bonding or by other means known generally in the art. Elongated weight  32  preferably consists of a length of rebar which has been treated to be rust resistant, although any elongated and relatively heavy member may be used. The weight of weight  32  should be large enough to ensure that bottom end  30  of curtain  22  remains at bottom  14 , even if water currents or flash floods act on the curtain. If a single piece of rebar is insufficient to anchor device  18  to bottom  14 , then as many as three or more individual pieces of rebar can be joined together in a parallel arrangement by the means of bindings (not shown) and used in place of a single rebar weight. 
         [0013]    Curtain  22  is secured to float  20  by means known generally in the art. As mentioned above, float  20  may consist of an extra long section of pool noodle, in which case curtain  22  can be secured by forming a slit  42  part way through the noodle to central cavity  44  and then bonding an end of the curtain within the slit. Several suitable waterproof adhesives (such as contact cement) can be used to bond the end of curtain  22  within slit  42 . Slit  42  forms attachment point  24  which is positioned on the side of float  20  opposite ballast weight  26 . Ballast weight  26  can consist of a length of rebar which is bonded to the surface of float  20  by means known generally in the art. Alternatively, ballast weight  26  can consist of an elongated plastic tube  46  which is bonded to float  20  and which contains a length of rebar  48 . Ballast weight  26  should be heavy enough to rotate float  20  such that the ballast weight is submerged and attachment point  24  is clear of the water. Ballast weight  26  should be light enough to ensure that float  20  can float freely and support fabric curtain  22 . 
         [0014]    Referring back to  FIG. 1 , positioning attachment point  24  ( 24   a ) opposite ballast weight  26  ( 26   a ) is an important feature as it ensures that the action of waves (or water level changes) do not cause the curtain to be dislodged from bottom  14 . As waves sweep past the elongated floats, the elongated floats will rise and fall. Preferably, the height of curtain  22  ( 22   a ) is selected so that the float remains at surface  16 . Waves, such as wave  38 , will cause floats  20  and  20   a  to rise and fall as the wave sweeps through. When wave  38  lifts the float, as shown in the case of float  20 , the “upper end”  35  of curtain  22  which is partially wrapped around the float is exposed as the float rotates so that weight  26  is oriented upwards. This has the net effect of temporarily increasing the effective length of curtain  22  resulting in less lifting forces being applied to weight  32 . Likewise, when wave  38  passes (as is the case with float  20   a ), the float lowers, causing weight  26   a  to rotate and effectively wrap upper end  35   a  of curtain  22   a  partially around float  20   a.  This has the effect of shortening curtain  22   a.  Floats  20  and  20   a  can therefore rotate in response to waves having an amplitude of  36 , which is approximately equal to diameter  34  of the floats. The net effect is that curtain devices  18  and  18   a  effectively absorb the energy of wave action without transferring it to their anchoring weights. This keeps the floats visible on the surface  16  and also ensures that the anchoring weights are not slowly dislodged as a result of wave action. Furthermore, seasonal changes in water level can be partially compensated for by the rotation of the elongated floats. Again, this keeps the floats visible on the surface while also helping to keep the curtain devices anchored to the bottom of the waterway. 
         [0015]    Channel  15  is formed by placing curtain devices  18  and  18   a  in the correct orientation in a waterway. If the orientation of the curtain devices is selected carefully with regards to water currents, it is possible to position the resulting channel such that periodic water currents flow through channel  15  thereby keeping bottom  14   a  of the channel relatively free of silt. As best seen in  FIG. 2 , an artificial channel  60  can be formed along a natural channel  42  in waterway  40  by placing a plurality of curtain devices in an end to end arrangement to form parallel chains of curtain devices  55  and  56  through natural channel  42 . Artificial channel  60  will have opposite ends  50  and  52 . The positioning of the chains of curtain devices is carefully selected to ensure that a naturally occurring current is formed between ends  50  and  52  which keeps the artificial channel relatively free of silt. Positioning the curtain devices can be done by boat or barge with the ends of adjoining curtain devices being coupled together to form the chain of curtain devices. 
         [0016]    The present invention has many advantages. Firstly, the artificial channel formed will be clearly marked by the curtain devices, providing a useful navigational aid to boaters. Since the curtain devices are not rigid structures, no damage will be done to either boat or the curtain device in the event a boat accidentally crosses over the floating portions of the curtain devices. Also, since the flexible curtains are flexible, they can easily withstand storms and waves without causing them to lose their anchorage. Finally, if the orientation and positioning of the chains of curtain devices is carefully selected, a virtually maintenance free permanent channel will result which does not require periodic dredging. 
         [0017]    The device of the present invention has other uses. Strategic placement of the devices allows for other applications such as the prevention of river bank erosion, the prevention of lake shore erosion, the containment and control of environmental spills and the protection of fish habitants. Other applications of a shore line or water way conservation nature can be devised for the device. 
         [0018]    A specific embodiment of the present invention has been disclosed; however, several variations of the disclosed embodiment could be envisioned as within the scope of this invention. It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims