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<br />SHORT ROCK JETTY HARDPOINTS <br /> <br /> <br />I"",,,. <br />"",.IIII!I '1rft'n~!I~:,lllld~':. <br />"''',lill,'III..''....,,.'','''I'''''',...,:!IIi1'. <br />.,."""",.". <br /> <br />---~~:---------{ -- <br />~ <br />I. ,::;J~ <br />\111'!.'t" "..'u,,,. 'I, <br /> <br />''OJ,,, <br /> <br />II II <br />\ \ <br /> <br />"'11111111"" <br /> <br />, <br />\ <br /> <br />'''I, <br /> <br />-~~ <br /> <br />\ <br />.\ \\ \ <br />--------------- <br /> <br />,\ <br />" <br /> <br />/ <br />~ <br /> <br />------- <br /> <br />/ <br /> <br />~ <br /> <br />---------- <br /> <br />""!lla'"".<!,llr..,l,, <br /> <br /> <br />Topsoil ,( seeded <br />Norma I <br />Water: Surrace <br /> <br />Stone Till <br /> <br />TYPICAL SECTIOAl <br /> <br />Hardpolnts are effective In deflecting the current away from the eroding bank. A series <br />of jettIes along the bank tends to create back currents between the jetties. This <br />produces a siltatIon of foreshore between the projecting dikes of rock. Rock should be of <br />sufficient weight to resist the river current. <br /> <br />The hardpotnt jetty consists of stone-f III structures placed intermittently along an <br />erodIng bankllne. The jetty is placed to protrude a short distance Into the river channel <br />near the norma I water surface leve I. A root sectIon shou I d be constructed I nto the <br />bankl Ine to provide protection to prevent stream cutting action behind the hardpoint. For <br />best resu I ts a ser I es of hardpo r nts can be used. Back currents are formed a I low I ng <br />siltation to occur. This wi I I provide added bank protection. <br /> <br />ADVANTAGES: 1) No requ I rement for sediment deposit In hardpolnt field. <br /> 2) Impermeability al lows reduction of erosion force of stream. <br />D I SADV ANTAGES: 1) Heavy equ I pment requ J red for construction. <br /> 2) Moderate I y high first cost. <br /> 3) Difficult to construct where access Is limited. <br /> <br />17 <br />