Management of the Israeli Coastal Sand Resources
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National Institute of Oceanography ISRAEL OCEANOGRAPIDC AND LIMNOLOGICAL RESEARCH LTD. Tel Shikmona, P.0.Box 8030, HAIFA 31080 Management of the Israeli Coastal Sand Resources 1.0.L.R. Report No. H28/1999 by Abraham Golik and Dov S. Rosen November, 1999 MEDITERRANEAN MINISTRYOF ACTIONPLAN ENVIRONMENT UNEP ISRAEL Management of the Israeli Coastal Sand Resources Summary and Conclusions in Hebrew 1Jr<rnn ,/r<1rn,11 ri1nJ /1n 11 /1111J nupmn rr'xnn llll .TIJTl p,/u DillJN TlDm ]lJ,nil D'll /[JJ ,/t<.lW,il C]lnJ D,'7Dl9il tr-mun D,J,/ilnil nN·J,:1:m ill n"lT TI,TITilJnil .tr nm n,ip 1nrn111 llDnil nJ1Dn/ nn/ imrn .cim11 ID TITt<.ilnustnn nN :]il 1,m~/lJill n"lTil nlljlTITI .D19lnil j)WTJTJnl1J1TTJ nD,Jj)/ ,D11DTTJD,N~TJTJID 11n1JJ mu.m n-xnm .Im p"nn 20-J rrtnnn rtrumnn rn~lil tr unun ilNnJ • TlilnJ nsnrunn ilJ'N J1w1 trum n1JJTJ ,r ID il1J'7J nsrm:n il11JJ 1J11~/ 1r:irnJ rim/ ilNJlilW /mil nm.m w1/WJ rrnrm n mm .rnnn 11rn1 /mil nmm 19lnil TIPJ N~m /mil 1rnn lJ/ .C9lnil Pl~lJil n11/Jl TillTillJ ilDTiil) ,DJtl lJTI /W lnD9UJil /WJ ,T'nDJ rr'irm /rn nj790N Dl~TJ~l m-rnnn TIJlJI .]lDl,JJ TINTI,91Tiil J~TJJ illlJTiil il119~ .rnn runsn ,J,TI ,91TIJ TI1191TID,JJTJ nnprr ]NlON .urn ,TD~ ltlj)J' NI cimil w Im n,//J 11rm1 rnrrr rn:':Sm NI .ismr /mil 1rnnJ llDTJil J:':Snnnn/ • l,JW C]lnil Dtlj)J lTJ il.A'TIJnn11j7 TIN DlT' NI .TI119W/ TDl TI,j7,T1J1TJllTil lj)/TIJ Dl'.li/il milrn mwn ill cim Im n~n 1ne<. ri,~1 Jpun u~J/ p/mm ,n,'7nD1 D119W .TI1i1'71nrJ D,J9il n-r n'Dj/lj/ ID (j/"l]TJ TlN,'7,n 4-J) TI,l'JJlJ'TO /W nlTJl:':SDmum nrn1~n nnn/ • n JJUJ il/N TI1t1m1TTIIm Tin,,1J ne<.llON/ p/nm :n 30 '7UJn-r pmu/ TD TlTlil IUJ n,TITI' PT ill'JDDJ ilTilJTJil ,Im j7"TJD]r/,TJ 500-J .C]lTIJ '71nil '711/T/ nrun /l:':S,J mrm-r pnJ/ p/mn 'TJ 30-n /n.:.i TI,n pnui; numn ci1n.1u TI111~n ,flJ .ilTIm D1JJn r'7 rrrsn n mm /UJ nrrc nr TI11r:irnD1JJn ,,,D nJ/J ·:nnP"nn W'71n 12-J • ir nnrr ill 'Im /w m111J nnrnr:iN pnJ/ p;nm .m mmm TI1'7m nn TI1'7n.:.i .j7'710 ilJTJTJn,91Tiil ilDTiilil nJlDD/ n//mnnil ,HJ illDO .mm nrum 1r ID TNTJD9UJm 'llnil 11rn'7 lrnil r nnn J~p • rummr n'7 rmum 'Im mm n-rr 1r:ionJ u,Tiill n'xntm .rrn m TI1JW10-'7 nnN .u=run rn rnrsmr ilJWJ rurnn D1w1n TI'JJn nnpnu p/mn n,,r:im trrm 1,1 ilJlil '7mil nrJ/ nJ111 • ilDTiil/ j/Tlil nN lDTTJ/ ,TJ ,lTINil n~/ ilJJlJil /UJ TTINil n:::sn Im rrunrn mil 111nN11 ilTW 1rJ1 ,m11J'7 J:::sp'7 ililT nrrr. 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Rosen Executive Summary This report presents the natural processes active along the Mediterranean coast of Israel, extending between Ziqim in the South to Haifa in the North, and assesses man impact on the coast. The purpose of this report is to provide the national planning authority scientifically based guidelines for formulating a coastal and sand management policy in Israel. The evaluation of the present sedimentological conditions along the coast is based on the integration of three methods of analysis: (a) comparisons of aerial photographs depicting changes of waterline and beach bluff or lower cliff line during the past 4-5 decades, (b) seabed volumetric changes determined from depth differential charts of redundant surveys, and (c) longshore sediment transport assessment using wave data. The analysis of waterline changes in three sites, remote from coastal structures or other antlrropogenic influence, did not reveal any constant trend of coast erosion, but more a fluctuating pattern, closely linked with the occurrence of extreme storms. These sites are located between Ziqim and Shefaiim, implying that at least from Shefaiim southward no general coastal erosion has occurred. It is not known whether overall coastal erosion occms north of Shefaiim. Local impacts due to coastal structures are usually represented by the trapping of sand to the south and erosion to the north of the structures. North of Hadera this trend is reversed. Entrapment occurs north of the structures and erosion is apparent on their southern side. The analysis of bathymetric changes which occurred in the areas studied shows that sand accumulation occurred in the area south of the structures. It implies that the long-term net littoral sediment transport in the study region is directed northwards. This complies with most of the results of the shoreline analysis as well as the results of the sediment transport rate derived by computation of the wave energy flux. This analysis also shows that sand entrapment near coastal structures is a stochastic process. The volume of sand deposited during a severe storm, occurring once in LO years or more, which lasts only a few days, may be equivalent to the volume deposited in one or more "normal" years. 1 The long-term mean rate of the net longshore sand transport, is assessed to be some 400,000 m3/year at Gaza going northward, decreasing to about 100,000 m3/year at Haifa, still northward. On the other hand, for the period 04/94-03/99 the approximate yearly averages were: at Gaza 400,000 m3/year northward, at Ashdod 188,000 m3/year northward at Hadera 26,000 m3/year northward and 100,000 m' /year southward at Haifa. Due to the shift in the orientation of the coast as well as the shift in the direction of incident waves along the coast, there may be periods of reversal in net transport confined to shallow waters (0-3 m depths) in the region north of Shefaiim. In very general terms, the net input of sand from the south by longshore sand transport is 400,000 m3/year and input from the coastal cliff erosion about 200,000 m3/yeru-. The sand loss to Haifa Bay is 100,000 m3/year, leaving 500,000 m3/year unaccounted for. The reduction in longshore sand transport volumes between any two adjacent sites means that there should be a long-term coastal accretion growing northward along the coast. As this is not the case, it means that the volmnetric difference is transported offshore, or onshore or to both offshore and onshore. Since sand on the sea bottom is confined to water depths less than 30 m, one must pursue the other options. Hence, even though we can not quantitatively prove it, by circumstantial evidence we conclude that a significant part of the cross-shore net transport is blown to the land by wind. The other part is transported outside the surf zone. Records show that prior to 1964, some 10 million m3 of sand were mined from the beach for building purposes. In addition, 12 million rrr' of sand were trapped behind coastal structures. The long-term (20111 century) mean of anthropogenic sand removal from the Israeli coast stands therefore on 220,000 m3/year, which is more than a third of the annual input to that coastal system, resulting in a negative coastal sand balance. This, with the forecasted reduction of sand input from the south due to the effect of Aswan Dam, and coastal structures built on the coasts of Sinai and Gaza, put the Israeli coast and its sand resources in a precarious situation. Despite the huge sediment quantities (~ 4 billion m') estimated to be present on the inner continental shelf (in water depths less than 30 m) it is recommended that mining in that area should be prohibited as it will deplete the beach sand. Exploitation of some 500 million rrr' of sand, found under a relatively thin cover of silt and clay at water depths greater than 30 m should be examined.