Device and method for coastal erosion mitigation using concrete dome structures

Abstract

A pre-cast concave dome device mitigates shoreline, river-bank, or lake-edge erosion. The dome approximates the outer quarter of a sphere and is cast from reinforced concrete with a wall-thickness gradient, heavier adjacent the base and lighter near the apex, to create integral ballast. An apex vent opening, subdivided by converging radial reinforcement, is dimensioned to admit ambient water and suspended sediment while excluding large organisms. After installation in shallow water, incident waves are redirected and dissipated by the curved exterior; sediment entering through the vent settles inside the dome, progressively increasing mass and anchoring the structure. Multiple domes can be arranged in staggered rows or layered arrays to tailor attenuation performance. Methods of deploying the domes and systems of plural domes disposed in offset rows are also disclosed.

I claim: 
     
         1 . A device for erosion mitigation comprising:
 (a) a concave structure defining a planar base and an apex; and   (b) a vent opening located at the apex.   
     
     
         2 . The device of  claim 1  wherein said concave structure is shaped as an outer quarter of a sphere. 
     
     
         3 . The device of  claim 1  wherein said vent opening is sized to allow passage of ambient water and suspended sediment thereby creating a combined concave structure and sediment whereby the mass and stability of said combined concaved structure and sediment is increased. 
     
     
         4 . The device of  claim 3  wherein said vent opening is configured to exclude flora and fauna of a desired size thereby avoiding danger to humans or marine life. 
     
     
         5 . The device of  claim 1  wherein said concave structure is thinner at said apex and thicker at said base. 
     
     
         6 . The device of  claim 1  further comprising a plurality of radially oriented reinforcing members extending from said base toward said apex and a plurality of circumferential reinforcing members intersecting said radially oriented members. 
     
     
         7 . The device of  claim 1  wherein said concave structure is configured to be placed into a body of water wherein the depth of said body of water at low tide is lower than the height of said concave structure and wherein the depth of said body of water at high tide is higher than the height of said concave structure. 
     
     
         8 . The device of  claim 1  wherein said concave structure is configured to be placed into a body of water at a depth equal to or greater than the height of said concave structure. 
     
     
         9 . The device of  claim 1  wherein said concave structure is comprised of concrete. 
     
     
         10 . The device of  claim 1  wherein said radially oriented reinforcing members meet in the vent opening thereby restricting entry into said vent opening by marine animals and humans. 
     
     
         11 . A method of mitigating erosion comprising:
 (a) providing at least one device comprising:
 i. a concave structure defining a planar base and an apex; and 
 ii. a vent opening located at the apex; 
   (b) placing said device on a submerged substrate with said planar base oriented generally horizontally; and   (c) allowing ambient water and suspended sediment to enter said vent opening whereby sediment accumulates within said concave structure.   
     
     
         12 . The method of  claim 11  further comprising repeating steps (a) (c) whereby a plurality of said devices are placed on said submerged substrate. 
     
     
         13 . The method of  claim 11  further comprising placing a first row of said devices at a first distance offshore and a second row of said devices landward of and laterally offset from said first row whereby a two-layer, shore-parallel array is formed. 
     
     
         14 . The method for erosion mitigation recited in  claim 11  whereby a plurality of said devices are arranged in first and second adjacent rows, said apex of each said device of said plurality of devices in said first row being laterally offset relative from said apex of each said device of said plurality of devices in said second row. 
     
     
         15 . An apparatus for mitigation of erosion comprising:
 (a) A dome structure, said dome structure having a convex outer shell surface and a circular base, a concave inner shell surface, said outer shell surface and said inner shell surfacing forming a domed roof having a peak; and   (b) a vent hole provided at said peak of said domed roof.   
     
     
         16 . The apparatus for mitigation of shoreline erosion recited in  claim 15  wherein said roof is thinner at said peak than at said base. 
     
     
         17 . The apparatus for mitigation of shoreline erosion recited in  claim 15  wherein said domed roof is comprised of reinforced concrete and wherein said vent hole is portioned to create a plurality of openings. 
     
     
         18 . The apparatus for mitigation of erosion recited in  claim 15  wherein said dome structure is a quarter-sphere. 
     
     
         19 . The apparatus for mitigation of erosion recited in  claim 15  wherein said dome structure is deployed in water along a shoreline or bank. 
     
     
         20 . The apparatus of  claim 19 , further comprising a plurality of the said dome structures deployed in water along a shoreline or bank.