PROTECTING COASTS AGAINST PROBABLE SEA LEVEL RISE USING POROUS VERTICAL SEAWALL

E l - Sadek M . Heikal, A yman S. Koraim, A hmed A. Abo Zaid

Abstract


There are three main parameters affecting on seawall crest leveldetermination: tidal range, wave run-up and sea levelrising.In thispaper,thehydrodynamicefficiencyofa new typeporous seawallisexperimentallystudied. This is byusingphysical modelsto minimize the run-up at the front of the wall. Theseawallconsistsoffront screen (steel screen suspendedon nearly spaced piles), back solid wall andfilled rock-corein between the two walls.The hydrodynamicefficiencyof theseawallis presented as a function of the waverun-up, reflection, and energy dissipation coefficients. Differentwave andstructuralparameters affecting theseawallefficiencyare investigated. The results indicate that;therun-up and reflectioncoefficientsdecreasewithincreasing ofrelative wave length (h/L),wave steepness (Hi/L), relative porous media width (B/L)and porous media width-water depth ratio (B/h).The energy dissipation coefficient takes the opposite trend.The efficiency ofthe proposedporousseawallin reducing wave run-up and reflection coefficientis better than theimpermeabletypeby about10to25%and 20 to 40% respectively.In addition,it is better than the impermeable one in dissipating the incident waveenergy by about 30to 60%.The increasing of the porous media widthhelps inreducing the wave run-up and reflectioncoefficient and increasing the dissipated wave energy by about 5 to 10%, 10 to 20%and 5 to 20% respectively.Theempiricalequationsare developed to estimatetherun-upand reflection coefficients. The results of these equations compared withtheexperimental results and it give a reasonableagreement by about 80 to 90%.

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