NghiAn cfia NGHINN CTIU HOAN LUU VINH NHA TRANG BANG TUO HiNH MIKE 21 CN Dinh Thi H6ng Vf,nr; KS Nguy6n Thdrnh Luin2 lTrudng Dai hoc Khoa hgc Tu nhidn thdnh pfrO HO Chi Minh 2ViQn Khoa hqc Thiy loi Vi6t Nam T6mtfit Nghi€n ct?u vi ddng chdy bi€n dqc bi\t td trudng ddng chdy ven bd tt| tdu dd chi€m duoc su quan tdm ct)a cdc nhd khoa hqc, cilng nhu cdc nhd qudn ty tqi cdc tinh thdnh ven bi€n, c6 Nha Trang, vi n6 ni dpng manh *'a da, diiu ki€n m6i trudng, cdc hoat d6ng vdn h6a - xd hpi - du lich crta cdc thdnh phti ndy Bdi bdo ndy thqrc.hiQn t[nh todn hodn lru cila vinh Nha Trang bdng m6 ttintn UtXg Zt cdc di€u ki€n di€n hinh KOt qud tinh todn cho thiil, ftaong ddng chdy tptng vinh Nha Trang chiu su chi ph6i manh md bdi.diiu kiQn dia hini ctte aO thfy triii c{ta khu vryc Ddng chdy theo mila bi chi pnili ctu; y€u bcti hQ thting gi6 mia, lru laqng nwoc s6ng khu vqrc K€t qud nghi€n cwu cfing aa pnithien ,a ,dng c6 su xudt hi€n cria cdc xoay sdt bd tqtihdi ne* aai pno ,r\iu i cd hai *,iro gb Abstract Studying oceanic currents, especially coastal currents has drawn much attention of many oceanographers and administrators in coastal provinces including Nha Trang city because they ltave strong impact on environmental conditions and cultural - socio - tourism activities of such cities The paper focusses on specific current distribution in Nha kang Bay in some typical conditions usiig the hydrodynamic module of MIKE 2I flow model and it has achieved several p^ftn" results Calculated results indicate that cunentfield variation in Nha Trong Bay is influenced by the shape of the coastline, bathymetry, tide, etc whereas seasonal circulation is mainly affected by monsoon and river discharge The results also show that there exist some inshore whirlpools when the tide changes its phase in the two monsoon wind periods I, D I E v i n rg D?t vdn tI6 Theo chiOu dai bd biOn hinh chft S cria ViQt Nam, phdn nh6 rar*ritv6 phia D6ng chinh ld vung C6t ffrann Hda (Bdn d6o Hon G6m) Su t6c d6ng xdm thuc sAu cria bi6n vdo lgc dia cflng nhu c6c ddy nrii dAm thEng bi6n tao n6n m6t bd bi6n Khrinh Hoa quanh co, khfc khryo, hinh thdnh nhi6u vfing bii5n vd vinh sdu kin gi6 thufln loi cho vi6c x6y dlmg cing birin vd ph6r tri6n du tich Vinh Nh; Trang ld mQt minh hoa ditin hinh cho ddc tli6m dia hinh n6u tr6n Ngodi n,hai Tap chi Khoa hpc Tdi nguy€n vd sdng ch6y qua dia phQn thdnh ph6 Nha Trang tl6u dO vinh Nha trang ld s6ng C6i (phia Bic) vd s6ng T6c @hia Nam) Hcrn th6 nfra, phia Nam vinh cdn c6 nhi6u ddo l6n nh6 V6i h6 th6ng di.a hinh phric t4p kt5t trqp v6i nhi6u y6u tO khric (gi6, thiry tridu, ) tao n6n nhirng n6t d{c tnmg rdt dia phucmg cria hodn luu vinh Nha Trang Vinh c6 hai mia 16 r6t, mia kh6 k6o ddi tu th5ng dtin thrlng 8, mta mua k6o ddi tu thhng d6n thing t2 NhiQt d0 binh quin hdng ndm ld 260C, hQu M6i trrdng - Sd B - ndm 2014 89 .,= NshiAn crhu nong nhAt 390c, lanh nhfu l4oc vung bi6nNha Trang noi ri6ng vd r,ung bi6n ViQt Nam n6i chung chiu inh hucrng mpnh cua y6u tO dia hinh vd hq th6ng gio mua (gi6 mta Ddng Bic, TAY Nam), Vi vQy, viQc su dgng m6 hinh to6n d€ m6 phong vd tinh to6n trulng ddng chiy khu vgc vinh Nha Trang theo ch6 dQ gi6 mia vd x6c dinh c6c dic tnmg cria trudng ddng chdy phUc vU cho c6c ho4t dQng b6o vQ m6i trucrng, kinh t€ x5 hQi cfrng nhu vdn hoa - du lich cua rung vinh Nha Trang co y nghTa thi6t thlrc v€ khoa hgc vd thlrc ti6n 2.2 SA liQa s,fr dqng tlgu dia hinh: nghiOn criu dd su dung tdi liQu d4c dfa hinh ndm 2006 ctra Li6n dodn Dia cnat UiCn v6i ti lg ld : 100.000 vor cilcducrng d6ng mric 1m He quy chitiu UTM, zone 49 D0 sdu kh6o s6t ld tu m6p nudc t6i d0 sAu 30 m SO tieu trucmg gio n6n: So ligu su dung dC x6c dinh chc dic tnmg th6ng kC cira gi6 dugc thu thflp t4i tr4m Nha Trang thdi gian 11 ndm (1988 1999) vd trucrng gi6 tu Trung tAm dU b6o m6i trucrng thuQc co quan quin li dpi duong vd quyCn MY G\ICEP Ph4m vi nghiOn crfru vh sii tipu sfr NOAA) dung SO 1i9u mr,rc nu6c, dong chiY: Nghi0n cuu dd su dung sO neu d4c muc 2.1 Phgm vi nghiAn cftu nu6c gid cita tr4m CAu D6, thuQc Vien Vinh Nha Trang c5 diQn tich 507 kmz, Nha Trang vdo thSng nim phia D6ng thdnh ptrO Ntra Trang, HAi ducrng hoc 12 ndm 2012 Nghi6n cuu su phia Bic dugc gi6i hpn boi vinh Binh vd th6ng dUng s6 liQu d4c ddng chAY I Cang, phia Nam ld vinh Cam Ranh (tu 24 - 251712012) tqi vinh Nha Vinh nim khu vr;c c6 kinh d0 tu ngdy l09ol2'E - 109020'E, vi d0 ti 7209.'E - Trang XAy drlng md hinh tofn 12018'E V6i diqn tich m[t nu6c xdp xi Hien tren th6 gioi co r6t nhiit 147 knf , vfnhNha Trang dugc che chdn ld dio 16n nh0t m6 hinh co th6 sir dgng dC m6 Ph6ng bdi 19 d6o lcrn nh6, d6o cn6 eO thuy dQng lgc vdng cua sdng ver Hon Tre rQng khoing 36 km'? bi6n Trong bdi b5o ndy nh6m t6c gid dt su dung m6 hinh MIKE 21 FM m6 durthriy dQng lqc dO m0 Phong hodn lr" vinh Nha Trang 3.1 ThiAt Qp miin tlnh Trong nghiCn ciru tinh to6n m6 hir:* cira s6ng vd ven bd n6i chung, vi6c thii: lflp m6 hinh, lua chon miAn tinh tod:J-4${*) f*\lu6i tinh to6n ld buoc quan.ffong qui;v/ / ( I 'i',L{/^rJ dinh khn n[ng cf,ng nhu chdt lugng c; I md hinh Mi6n tinh to6n Phii dim t'": kh6ng qu6 nho dC tr6nh nhirng inh huo: = cira c6c diOu kien biOn toi vdng nghri: ciru, ddng thdi ktr6ng dugc qu6 16n r i 'i d6n t6i khOi tuqng vd thoi gian tinh tc.r qu6l6n, hon nira di€u kien biOn thi6t -r: nghi€n cr?u phAi b6o ddm Phu h.:: Ifinh I V! trl ving nghidn cftu 'sli SO vo: ;.::=#:: l.it-# ti€: ,, nh "rq r^'oli -,, := -\_Pt: trf Ll- ii-r -: - :.:-.:: ::.:::::: :.:::::*=.: ::.=:::: ." .:.== 1.=:.= *' iqlilllll =;8": ffi #:: iG! G ffi IF -G: *G *r Moi tradng - 56 03 - ndm 2ol4 r ! - ::::::r = :, i'{"1-{" / @rd ::_ ' ma :.!:: -:=i"" #; il r iiilllflilli NghiAn cftu v6i chc s6 tlQu quan tric hoflc tinh to6n Lu6i tinh to6n cf,ng phii d6m b6o tlir chi tit5t O nhimg khu vuc cAn nghidn cr?u vd phii ph6n 5nh dugc dir mric tlQ chi ti6t vC dia hinh, ohtmg n6 kh6ng qu5 thua vi c6c ytiu t6 dQng lgc chiu su chi ph6i mAnh 3.2 KAt qud hiQu chinh vd kiAm dlnh mqtc nwfc vd ddng chdy cfia mO hinh - ftit qui hi6u chinh, ki6m tlinh ducrng qu5 trinh muc nu6c mE v0 dia hinh Vcri c5c ti6u chi trdn mi6n M6 hinh dugc hi6u chinh v6i tinh to6n khu vuc nghiOn cr?u k6o ddi tu Bdi Ti6n t6i vring Cam H6i D6ng bao trum hCt dunng bd cira vinh Nha Trang (kC ca chc dho lon nh6) Gicri han kinh d0ld 303045 + 320650 m, gi6i hpn vidQ ld 1341351 + 1360796 m theo hq UTM (hinh 2) Lu6i tinh dugc xdy fimg ld lu6i tam gi6c phi c6u trfc g6m 6344 nit, 11265 phdn tu (hinh 3) liQu mgc nudc t4i trpm CAu D6 dqt fi 2017 - 251712012 Sau d6 duqc ki6m dinh lai v6i muc nu6c dac tu 25112 30tr2120t3 s5 &**** Ilinh So sdnh dao dQng mgc nubc ilgc vd mb phong biing m6 hinh tgi tgm Cda Dd - Nhu Trang, thdng 7/2012 Ifinh Ilinh Dudng tting mftc tlla hinh vilng So sdnh dao ttQng myc nmlc ilgc vd m6 phdng bdng mO hinh tgi Cdu nghidn cftu Dd - Nha Trang, thdng 12/2012 Bdng HQ sO twong quun giira sa ngu J : ^ quan trdc vd sO liQu trlch xudt tir k0t qad m6 hinh He so tuong quan Mqc nufc thilngT Mgc nuric th6ng12 Nash (%) 92,8 88,3 - KOt qui ki6m chimg trudng ddng chiy Ilinh Lt6i tlnh vd itla hinh ddy vlnh So s6nh trucrng ddng ch6y gifra ktit qui m6 hinh vd thUc tO cho th6y sU tucrng quan vd hufng, hu6ng chri dpo cua dong ch6y khu vuc dio ld Nha Trung Tqp chl Khoa hpc Tdi nguy€n vd M6i tradng - 56 03 - ndm 2014 9I NshiAn cftu hufng chdy tu Bic xu6ng Nam phd hqp v6i quy lu6.t dong chiy t4i pha tridu 16n tr6n thuc t6 cflng nhu tu kiSt qui m6 hinh tinh to6n dugc T6c d0 ddng tucrng d6i phi hqp vd nim khodng tu - 10 cm/s vd 10 + 15 cmls, chi6m tAn suAt kh6lon sudt chu ki tri6u Nhu vfly, c6 thO sir dung m6 hinh d6 nghiOn cr?u, tinh to6n c6c trudng thuy dQng lgc khu vuc nghiOn cuu Bdng Tgu itQ cdc trgm qaun trdc ddng chdy ving nghiAn cftu (tir 24 2s/7/2012) Trarn MRI MR2 MR3 MR4 Li6n tgc Tqa.l0 N E 12011',33,6 1090t2'48,9 12012'57 ,9 109013',17.1 120t2'11,8 109014'48,5 120l1',t2,4 109015',19.6 12010'51,6 109014',22,2 Thtri gian 24t07120t2 08:12 24t07 09:05 /2012 2410712012 1012 2410712012 11 :04 1A : 2510't 12012 IIinh So sdnh hoa ddng tgi trgm IiAn tyc (LT) chu ki triiu ngdy 24 - 25/07/2012 (a) Hoa ddng bdi may ddng tqrc ALEC (dt : 15s); lii' '=- L (b) Hoa ddng bdi mdy ddng tlrthdi AEM (dt: th); (c) Hoa ddng m6 hinh tinh toan dat': Ilinh 6, So ili (dt: cdc trgm khdo sdt vilng nghiAn cftu C X6t qui vir thio lufn Vung I ld khu v.uc g6c phdn tu phr: tr6n b6n phii cira miAn tinh tuc ld doa: nim gi6i hpn bi6n Bic, nira tri: cira bi6n E6ng vd dudng bd phia Eong Bic cua dAo Hdn Tre: ddng ch6y trons ch,i fnoa l{"v', th) Cdn cri vdo dflc di6m phAn bO cu: truong dong chiy vr)ng nghid: cuu, c6 thd chia vinh Nha Trang thirr b6n virng nhu hinh du6i ddy: fqp hpc Tdi nguyAn vd M6i trudng - Sd 03 - ndm 2014 D -,,, vr)ng -.-' haik gi6 r: "" th6ni ch61 : chhz Vi6c., hcrn , , tai tt:ld tri.'" ' :": NshiAn cfiu ving ndy tucrng eOi yeu vd chri y6u c6 hu6ng D6ng - TAy Vtng II ld r,ung bi6n tu Bdi Ti6n d.5n mfri Chut vd mdt phAn bo d6o Hdn Tre: ving ndy thucrng c6 t6c dQ dong khd lcrn, hu6ng ddng tdp trung theo hudng DOng BEc -Tlry Nam Ving III ld khu vuc bao quanh boi ving tu mfii Chut d€n Mfli D6ng Ba vd m6t phAn duong bd d6o Hdn Tre, khu 4rc ndy c6 nhi6u d6o nho: dong chiy tpi day bf chi ph6i m?nh boi dia hinh Vung IV ld vung cdn lai tuc ld phdn duoc bao quanh boi nria du6i bi6n D6ng, ducrng bo d6o Hon Tre cdn lai vd bi€n Nam: khu 'u,uc ndy ld noi ti€p gidp cta vinh Nha Trang v6i vinh Cam Ranh, su trao d6i nudc di6n kh6 rd n6t vd t5c dQ ddng o ddy cfing kh6 m4nh t?'rary lO9-Js?,f' F crn riirn toto F"" hs lltn rfug t@g Ifinh So itt phdn chiu ving bi6n nghiAn crhu DC d6nh gi5 ch6 dQ thiry dQng luc vung nghiOn criu, bdi b6o tfnh to6n cho hai kfch bin ld m6 phong thdi kj, gi6 mia D6ng Bic vd gi6 mua T6yNam th6ng qua vi6c d6nh gi5 vC CO lcrn ddng chiy pha tri6u l6n vd pha tridu xu6ng o chhai thdi kj'tridu culng vd tri6u kiQt Vi6c xem x6t ndy nhim dhnh gi|chi ti6t hcrn v€ sg thay d6i d9 krn ddng chiy tpi tung thoi di6m V6i bi6n phia biOn h triAu ds tinh tu bQ hing s6 di6u hda, Tap chi Khoa hoc Tdi nguy€nvd bi6n s6ng ld luu luqng dong ch6y trung binh Do tinh phirc tap virhpn ch6 vO s6 1i6u n6n nghidn cr?u ndy kh6ng x6t 6nh hucrng cria s6ng K6t qu6 m6 ph6ng c6c kich bin duoc the niQn cU th6 cilc phdn tich du6i ddy _4.L KAt qud tinh totin mia gid DOng Bdc Tridu cudng: huong ddng tri6u l6n chir y6u h hucrng Tdy Nam, ddng ch6y t6ch ldm hai di vdng qua d6o Hdn Tre Ddng chhy phia Tdy di qua eo nh6 (khu nuc 3), tdc dg ddng tdng 16n Trucrng dong chiy hufng Tdy Nam (tri6u l6n) t6n t4i lAu hcrn vd manh hon truo:ng dong chiy hu6ng Edng BEc (tri6u xu6ng) Tri6u kiQt: hai giai doan tri6u l6n vd triAu xu6ng d6u r6t y5u Dong ch6y todn vung tri€u l6n c6 hu6ng T6y Nam r6t 16 rdng o giai doan triAu xu6ng hufng ddng chiy nguoc lai (D6ng Bic) 13i kh6ng 16 rdng Lric ndy, ddng chiu t6c ddng rd rQt bOi hu6ng vd t6c dQ cria gi6 Phdn tich sg bi6n COi AOng chdy m6t chu kj.tri6u ngdy 16 - Illt2l20l2 tai citc vtng cu th6 vinh cho th6y: Pha triiju lOn: ddng chiy chtr y6u hu6ng Tdy Nam xu th6 hufng vdo bd, v6i t6c dQ ddng tu + 15 cm/s (vung I), 25 - 35 cm/s (wng II) Do ddc tli6m dia hinh vd dAo chin ddng chiy theo hudng Nam - DOng Nam (vung III) , TAy - Tdy Nam (vdng IV) D6ng thoi t6c dQ ddng chiy cfrng bf thay eOl theo tlng vi tri chiu 6nh hucrng dia hinh vd etdo o mdi drg, cU th6 t6c d6 dong dat + cm/s, c6 vi tri 20 + 25 cm/s (vdng III),25 + 40 cm/s (rung IV) Pha triiju xu5ng: dong chdy c6 hu6ng ngugc lpi vd t6c d6 dong chdy thAp hcrn so v6i pha triAu l6n o mdi virng M6i trudng - 56 03 - ndm 2014 NghiAn cfia Ilinh So iI6 phdn bii dang ch,fiy tgi thdi cliAm triiu ftn mgnh tr.ong tnn nigid mia DOng Bdc ddng ch6y tucrng d6i l6n Hu6ng dong tri6u l6n ld hu6ng ru D6ng Bic - Tdy Nam ch6y doc theo bo Tuong tu nhu mta gi6 D6ng BEc, dong nu6c tu ngodi khcyi chia ldm hai nh6nh di vdng qua ddo Hdn Tre vd tho6t xu6ng phia Nam (hinh 11) Tpi thoi di6m d6i pha tri6u, t6c d0 dong chiy nho tr6n todn vinh, r6i ddn xudt hi6n cic xohy cuc b6 tai bo Tdy Hdn Tre vd mQt sii khu luc xung quanh cric mfri nh6 cira E6o Hdn Tim Hdn Mi6u Khi tri6u xu6ng, ddng ch6y c6 hudng nguoc lai, nu6c tu phia Nam dua 16n, t6i Hdn Tre t6ch ldm hai don" chhy di vdng qua ddo Tridu kiQt: vdo thdi gian triAu ki6t, b6n nhft tri6u th€ hi6n 16 rdng, ddng chiy lirc ndy y6u hcrn so v6i tri6u cudng, ddng ch6y bi dnh hucrng nhi6u bcri hucrng vd t6c dQ cria gi6 Hu6ng gio chri dao hic ndy ld E6ng Nam Hu6ng ddng tuTdy Nlm l6n D6ng Bic tai pha tridu xu6ng chi6m uu thd hcrn ddng cl6y theo hufng nguoc lai pha tri6u l6n IIinh -10 So ili phdn ba ddng chdy tgi thdi diAm triiu xu6ng mgnh inn gi6 mila DOng Bdc *i Nhu vQy, vdo mta gi6 mria D6ng Bic, pha tri6u l6n chiem uu the vE thdi gian k6o ddi vd t6c dQ dong ch6y Hu6ng ddng manh nhAt ctli yt5u c6 hufng fu phia BEc chhy xu6ng Nguy6n nhdn chri yt5u ld dong chiu s1r-chi ph6i cria dia hinh, trudng gio tr6n vinh v6i hucrng gi6 chir dao lirc ndy ld hu6ng D6ng B8c 4.2 Num Kd qud tfnh totfin mila gi6 TAy Triiju cuong: tri6u l6n xu6ng 16 rdng vdo thdi di6m ddng cuc dai v6i t6c d6 '-l : Ifinr thdi Qua ddy c6 thd th6y, vdo mta gio mta TOy Nam, trudne dong ch6v hucrns D6ng Bic (tri6u xuOig.) tO" tiii"" rt"i vd manh hcrn trudng dong chiy hu6ng TAy Nam (tri6u l6n) I ,"*li Phdn tich sU bi6n OOi AOng ch6y cho hing !