Md ptiong lan truyen dp due theo mua ci vung ven bien Do Sdn

K h o a h p c TLJ nhien

Md ptiong lan truyen dp due theo mua ci vung ven bien Do Sdn - Hai Phong va khu VI/C ian can bang mo hinh toan 3 chieu

S 7 -z-r 2-3

Hh Vift Cwoug"', Tr^n Anh TiiS Pham Hai An^

' Vi^n Khoa hpc Thuy lai Vi^l Nam 'Vien Tdi nguyen vd Moi tncang bien

Ngay nl^in bai 24.9.2015, ngay chuyen phan bien 1.10.2015, ngay n h ^ phan bi?n 30.10,2015, ngay chap nhan dang 6.11.2015

Vung ven biln Bh Stm - Hai Ph6ng la nffi &o ra ciia ntiieu song (D'n ttiuoc h | thong song Hong - Tliai Binh nhir cac s6ng H^ng, Thai Btnh, Tra Ly, Ninh Cff, Van Uc, Lach Tray, Cam, Bach Dang... Vi v$y, su- lan truyen do due 6* vung ven bien Do Sffn va cac Ithu vuc lan can phu thuoc vao che do dong chay, van chuyen bun cat tur trong song ra va che do thuy trieu tur ngoai bien truyen vao. Bai bao trinh bay mot so ket qua mo phong qua trinh lan truyen d9 due trong vung biln Bo Sffn •- Hai Phong theo mua (mua lu, mua kift) biing mo binh toan 3 chieu Delft 3D.

Tdr khda: Delft-3D, lan truyen do due, viing bien Do San - Hdi Phong.

Chisd phdn loai 1.7

Simulation of seasonal turbidity transmission in Do Son - Hai Phong

coastal area and surrounding sites by 3D calculation model

Summary

The Do Son - Hai Phong coastal area is the region that receives river water of the Red River - Thai Binh system including the Red River, Thai Binh and Tra Ly, Ninh Co and Van Uc, Lach Tray, Cam, Bach Dang rivers, etc. Therefore, the turbidity transmission in Do Son coastal area and the surroundings depends on the flow regime, the sediment transportation from the rivers to the sea, and the tidal regime from the sea to the rivers. This article presents some results of the turbidity simulation in Do Son - Hai Phong by seasons (rainy season, dry season) with the Delft 3D model.

Keywords: Delfi-SD, Do Son - Hai Phong Coastal area, turbidity transmission.

Classification number 1.7

*Tdc gid lien he: Email.

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Yung bien Do Son - Hai Phong la nai do ra ciia nhieu song lon. d phia bac Do Son co cira Lach Huyen (song Chanh), Nam Trieu (song Bach Dang), Cam (song Cam), Lach Tray (song Lach Tray). Ci phia nam Do Son c6 cac cira Van Uc (song Van Uc), Thai Binh (song Thai Binh), xa hon co cac ciia Tra Ly (song Tra Ly), Ba Lat (song Hong), Nmh Co (song Ninh Co), Day (song Day) [1]. Hien tupng nuoc due a viing ven bien Hai Phong noi chung va cac bai tam cua thi xa Do Scm noi rieng ngay cang trd nen phuc tap, dac biet la tu thap ky 80 tro lai day, hien tugng due nuoc ngay cang gia tang [2-4]. Nuac 6 vung bien Do Son bi due lam 6 nhiem nuoc ciia cac bai tam va mat di su hap dan ciia khu du ljch Do Son, vi vay viec nghien cuu xac dinh nguyen nhan va tim giai phap khic phuc hien tugng due nuoc a vung bien nay dang duge quan tam nghien cuu. Bai bao trinh bay mot so ket qua nghien euu tren mo hinh toan 3 chieu Delft 3D ve dien bien ciia chg dp thuy luc dong chay, biin cat va qua trinh lan truyen dp due Of viing bien Do Son - Hai Phong theo miia. Cac ket qua mo phong se la co sa de nghien ciiu de xuat cac giai phap khoa hpc va cong nghe phii hgp nham giam thieu hien tugng due nuac cho vung bi^n D6 Son - Hai Phong trong tuang lai.

Tai lieu va phirong phap nghien ciin

Tdi lieu sir dung

Tai lieu dia hinh: s6 lieu dp sau va duong bo cua khu vuc ven bi6n thanh ph6 Hai Phong duge so hoa tif cac ban do dia hinh UTM ty le 1:50.000 do Cue Do dac ban d6 xufit ban.

Dia hinh khu vuc ven bi^n Hai Phong, Cat Ba con duge bo

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K h o a h p c TLT nhien

sung cap nhat so lieu do sau trong nhimg nam gan day ciia mpt so de tai, du an da thirc hien a khu vuc nay.

Do sau phia ngoai khu vuc ven bien thanh pho Hai Phong va vung lan can con dugc tham khao va bo sung tu CO so dii lieu dia hinh ET0P05 (Earth Topography - 5 Minute) eua Trung tam Tu lieu dia vat ly quoc gia My (National Geophysical Data Center - NGDC) \'a GEBCO-1 (General Bathymetric Chart ofthe Ocean (GEBCO) one minute) ciia Trung tam Tu heu hai duong hpc Vuang quoc Anh (British Oceanographic Data Centre - BODC).

Tai lieu khi tugng, thuy van: so heu quan trSe liru lugng, muc nuoc, song... ciia cac tram khi tugng, thuy hai van vung bien Do Son - Hai Phong.

Tai lieu bun cat: so Ueu quan trSc dp due tai cac ciia song va cac tram trong khu vuc nghien curu.

Phuomg phdp nghien cuu

Phucmg phap mo hinh toan sir dung de mo phong che dp thiiy dpng lue va lan truyen do due khu vuc nghien ciiu la mo hinh Delft 3D. Day la mo hinh dugc Vien Thuy luc Delft (Ha Lan) phat tri&i, c6 kha nang tinh toan va mo phong cac qua trinh dgng luc va van chuyen bim cat tai khu vuc eua song, vinh va vung bienvenbcF[5].

Thiet lap cdc mo hinh tinh todn: mo hinh thiiy dpng luc: pham vi nghien eiiu gom ban dao Do San, eae cua song va vimg ven bien tu Hai Phong den Nam Dinh Mien tinh cua mo hinh co kich thuac khoang 65 km theo chieu dong bac - tay nam va 42 km theo chieu tay bae - dong nam, voi dien tich mat nuac khoang 2.300 km- duge ehia thanh 310 x 508 6 luoi, kich thuoc cac 6 luoi bien doi tu 35 d6n 305 m', hiy thuoc vao timg khu vuc mo phong (hinh 1); mo hinh lan tiuySn dp due: mo hinh dirge xay dung tren ca so eac kkx qua tinh toan cua mo hinh thuy dpng luc, trong do co ciing pham vi mien tinh va luai tinh.

Cdc dieu liien t>ien cua mo hinh: bien phia ngoai bien: gom cac bien muc nudc. song, gio phia ta\ nam.

dong nam \ a dong bac duoc trich xuat tu ket qua tinh cuamo hinh toan \"inh Bac Bg: cac bien cira song: gom cac bien luu luong \ a bun cat cua 7 cira song chinh trong khu \ u c ' Bach Dang. Cam. Lach Tray. \'an Cc.

Thai Binh. Tra L\. Ba Lat dugc trich xuat tir kei qua tinh cua mo hinh moi chieu Mikel I-ST cho toan mang song Hong - Thai Bmh Ngoai ra. cac diem nguon thai ven bd (rl. r2. k l . k2. p i . p2-,. the hien tren hinh 1) Cling duoc dua \ao m6 hinh de tinh toan Buoc thdi gian tinh ciia mo hinh \ di Dt = 30 s.

Bang : ^'- :n Jo Sn .r-ingbinli iheo mua. lliU'i tap cho cac hiin cua song Gia t n dp due tnuig binfa p |'iiig,''T)

Hieii chinh \d Idem dmh mo hinh mo hinh duoc hieu chmh \a kiem dml? vdi chudi sd lieu thuc do ve muc nuac. sdng, do due cua tram Hon Dau \a tai mpt sd vi tri do dac khao sat cua de tai cap nha nuac KC08.34 11-15 Thdi gian hieu chinh \ a kiem dinh mo hinh nhu sau:

- Hieu chmh mo hinh \ en chudi sd lieu miia kiet rir 1.3.2014 den 31 3.2014

- Kiem dmh md hmh \ di chudi so lieu miia lu ui 1.8.2014 den 51 8 2014.

Kei qua danh gia sai sd giira tinh loan \ a thuc do cho tha\. he sd tuong quan muc nudc irong mua kie:

va miia lu lan luat cd gid tn 0,941 \ a 0.938 Sai sd binh phuang tmng binh (RMSE) cd gia tn 0.16" va 0.142 Nhu va\. sai sd na\ cd the chap nhan duae uong dieu kien dia hinh khu \Trc co tinh phdc tap \ a bien do dao dpng muc nudc lan Ket qua hieu chmh \ a kiem dinh mo hinh duac the hien a hinh 2 \ a hinh 3.

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Hinh I: pham vi ludi linh vd dia hinh khu vuc nghia thiit % tren md hinh Detfi 3D

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6(7)7.2016 20

Khoa hgc Ty nhien

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Mda kift (tic 4 3 din 12 3.2014) Miia IU (tic iigdy 7 8 din 15 S 2014) Hinh 3: so sdnh ket qud tinh todn dd dtfc vdi so lieu thvc dotal vi Iri B2.

khu vuc phia ngodi cua sdng Cdm vd ciia Bach Ddng

Ket qua tinh toan mo phong Mo phong trir&ng dpng ltrc, dong chdy Mda lii - pha trieu len: vao mua lii do luu lugng nudc tu trong sdng do ra Idn, nen dii trong pha tri^u I6n thi dong chay tir bien hudng vao cae cira song vfin cd van toe rat nhd. Trong pha trieu nay, hudng ddng chay chu yeu la nam - ddng nam vdi gia tri van tdc bien doi tir 0,21 den 0,65 m/s. 0 khu vuc cira sdng Van Uc, noi luu lugng nudc tir song Idn nhfit trong cae sdng do ra viing bien Do Scm thi hau nhu khdng ed ddng chay nguge tir bien vao, dong trieu va ddng chay lii eo hudng nguge nhau bi triet tieu va gay ra hien tu'png nudc dimg d khu vuc tnrdc cua sdng, d day xufit hien nhieu viing nudc quan dan den hien tugng lang dpng tram tich va tao nen cae bai bdi ngam. So sanh trudng ddng chay d tfing mat va tang day trong khu vue thay rang, anh hudng cua ddng chay tir eac cira sdng do ra la rat ldn, van tdc va hudng chay tfing mat phu thupe theo huang va lim lugng ddng chay ra tir eac ciia song (hinh 4a), trong khi tang day chiu anh hudng chii yeu eua eac qua trinh ddng Iuc biln theo hudng nguge lai (hinh 4b). Ci thdi diem nudc Idn, hudng ddng chay phfin tan manh me vdi gia tri van toe kha nhd, dac biet la viing nudc giira Hdn Dau, Cat Ba va Cat Hai.

a) Dang chdy lang mgi b) Ddng chay Idng day Hinh 4: kit <jud md phdng trudng ddng chdy tdng mdt

vd tdng day miia IS Irong pha tneu len

Mua IU - pha trieu xuong: sir ket hgp giua ddng chay song va ddng trieu dugc the hien ro net vao pha triSu xuong, tao ra ddng chay tdng hgp vdl van tdc kha ldn so vai cac pha trieu khac, hudng ddng chay trong

trudng hgp nay theo hudng tir eac cira sdng do ra phia bien. Gia tri van tdc dong chay bien ddi trong khoang 0,2-0,8 m/s, mdt sd nai do ldng dan hep nhu khu vuc cira Lach Huyen, cira Nam Trieu... van tde ddng chay tang mat cd thg dat 0,8-1,0 m/s. Trudng ddng chay trong pha trieu nay ed hudng tuong ddi ddng nhfit giua tfing mat va day do sir tuong ddng v^ hudng ehay cua ddng chay trong sdng va ddng trieu (hinh 5).

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a) Ddng chdy tdng mgt b) Ddng chdy Idng day Hinh 5- kit qud mo phong trirdng dong chdy lang mdt

Vii Idng ddy miia lii irong pha Ineu xudng

Mua Iciet - pha trieu len: vao miia kiet, su biSn ddi cua trudng ddng chay theo thdi gian d viing cira sdng ven bien ca ban cung gidng nhu trong miia lu. Tuy nhien, do cd su bien ddi miia cua trudng gid va su suy giam dang ke luu lugng nude tir cac sdng dd ra ciing da tao ra sir khac biet tuong ddi ciia trudng ddng chay cua mua kiet so vdi miia lu. 6 thdi ky cudi pha trieu len va nudc ldn, van tdc ddng chay kha nhd, su anh hudng ciia khoi nudc sdng vao thdi diem nay rfit han che nen khdi nudc bien xam nhap sau han vao phia trong cac cira song. Thdi gian chuyen pha giira nude Idn va thdi diem trieu xudng kha nhd, trong khoang 2 gid, dang chii y la trong thdi diem nudc ldn trudng ddng ehay d vung cira sdng ven bien kha ddng nhat ve hudng giiia cac ldp nudc tang mat va day (hinh 6).

a) Dong chdy tdng mai Hinh 6- ket qud mop,

vd tdng ddy mi

h) Dong chay lang day g iritdiig dong chdy tdng mat iiel Irong phu Ineu len

Miia kiet - pha trieu xuong: kht pha trieu xudng, ddng trieu khdng cdn manh nhu vao thdi diem trieu len nen ddng ehay tir trong song chiem uu the, dieu nay

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K h o a hupc TLT n N ^

thg hien rfit ro net d khu virc trudc cac cira sdng. Sir suy giam cua ddng tri6u vao pha trieu xudng se cd tac dpng lam tang kha nang phat tan dp due tir trong sdng ra phia ngoai bien (hinli 7).

a) Dong chdy tdng mat b) Ddng chay tdng ddy Hinh 7: ket qud mo phdng trudng ddng chdy tdng mdt

va Idng day mua ki?l trong pha trieu xuong

Md phdng qud trinh lan truyen dp due Mua Id: su lan truyen va phan bd dp due d viing cua sdng ven bien phu thudc rat ldn theo pha dao dpng cua muc nudc trieu, trong pha trieu len trudng ddng chay cd hudng tii bien Ifin vao eae ciia sdng, vi vay viing ed ham lugng dp due cao bi day ve phia sat bd. Doi vdi cac eiia sdng idn, do dong chay tu sdng ra manh hon ddng trieu nen ddng biin cat tCr cae cira sdng phat tan ra ngoai cd pham vi rdng 15-30 km, vung cd ham lugng do due cao (ldn hem 300 mg/1) phfin bd chu yeu tai eae ciia sdng nhu Van Uc, Ba Lat va mdt phan trudc cira Lach Tray va cua Cam (bang 2), chenh lech dp due giiia tang mat va day khdng ldn do sir xao trpn biin cat cua qua trinh dpng luc manh me ciia ea ddng trieu va ddng chay trong song (hinh 8).

Bdng 2. kit qud tinh loan gid tri do due lai mdl so \i iri irong mua IQ

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Cua Cam Cua Lach Tra^

Phia la> Cai Hai Ngpc Hai Bai iam 1

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Tai khu vuc bien ndng ngoai eac ciia sdng, ddng chay bi thuy trieu chi phdi va tae ddng eua ddng sdng trong khu vuc ddi sdng vd. Cang ra xa ddi sdng vd, vai trd ciia ddng triSu cang tang, dong vai trd chii yeu. Khi

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tridu dang, ddng chay dien bien phuc tsqj hon bdi vung nudc quan, ddng chay la ddng lii va ddng tri6u tranh chfip nhau, khoi nudc lu mang sa bdi dugc dfiy nguge lai phia bd, ddn ep vao ciia song, gdp phfin lam I0ng dpng nhanh bun cat la lung d nhung noi thuan Igi cd tdc dp ddng chay nhd. Hien tugng chay quan xuat hien manh d cac Iudng lach phy hai ben long dan chinh, gdp phan lam tang kha nang lang dpng bim cat, day la nguyen nhan thanh tao cac ddi cat, con ngam d cac ciea sdng va khu vuc lan can. Trong pha trieu xuong, sir phan tan do due tu luc dia ra phia ngoai vimg ciia sdng ven bien khu vuc nghien cuu the hien rd. Dudi tac ddng ciia trudng ddng chay, ddng dp due khdi^

ehi lan truyen ra phia ngoai bien ma con ed xu hudng dieh chuyen nhieu ve phia nam - tay nam theo hudng di chuyen cua cac khdi nuoc sdng. Khu vuc cd ham lugng dp due cao ngoai vimg sat cac cua sdng con xufit hien d viing ven bd ban dfio Dd Son (ca phia bac va phia nam). Trong khi dd, cac khu vuc nhu phia nam Cat Hai va Cat Ba c6 ham lugng do due thfip, dieu nay cbo thfiy ddng do due tir cae song thupe khu virc tinh toan it cd kha nang anh hudng den nhiing khu vuc nay.

Ket qua md phdng cung cho thay, su lan truyen cua dp due tren tfing mat nlianh han so vdi tfing day, dang chu y la khu vuc ven bd phia bac ban dao Dd Son ham Iugng tram tich d ldp nudc mat ldm hom rat nhieu so vdi ldp day.

c) Thdl diem nudc rdng d) Thai diem nadc Idn Hinh 8: ket qud md phdng qud trinh lan truyen dp due trong mua lu

lai khu vice cdc cua sdng vd vdng ven bien khu vuc n^aea cuu

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Khoa hgc TLJ nhign

Mua kiet: trong mua kiet lmi lugng va ddng chay tir trong song giam nhd nSn trong pha trieu Ien khdi nudc bidn cd ham lugng d0 due thfip (5-10 mg/1) se ti6n sau vao cac cua song trong khu v\rc, nhat la cac song cd Iuu Iugng ddng chay nhd nhu sdng Lach Tray va Thai Binh. Trong pha trieu xudng, ddng chay va ddng bun cat tuc trong sdng cd dieu kien thuan lgi de phat tan ra phia ngoai viing ven bien. Tuy nhien, do ddng chay va dp due trong miia ki$t nhd nen sir lan truydn dp diic tir cac ciia sdng ra phia ngoai bien bi han che di rat nhidu.

Viing nude cd dp due tucmg ddi eao (30-50 mg/1) ciing chi tap trung tai eae khu vuc sat bd cac cira Cfim, Lach Tray va Van Uc (bang 3).

Bang 3: kel qud linh loan gid Iri dd due tgi mpi so vi iri Irong miia ki^l

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Phln % Cil Hai NgflcHii B i i U m l B l i l i i i i 2 HtaDiii N r a i D i s ™ B i i i g U VInOc TMl Bbih

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Tniuxaimg 27,5 20,0 19.0 1.0 3,0 0,5 0.3 0.4 O.S 40.0 14.0

Dliil, nia 12,0 17,0 6,0 1.0 1,0 0,6 0,7 0,3 1.3 23,0 4.0

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31.0 20,0 44,0 34.0 17,0 4.0 0,9 0.3 0.1 70,0 35,0

Ngoai ra, do anh hudng ciia trudng ddng Iuc va tae ddng cua gid ddng bic trong kiet (miia khd) nen ddng due tir cac cita sdng cd hudng di chuyen chu ydu tir phia dong bfic ve phia tay nam va cd pham vi nhd hon so vdi miia lu. Ham lugng dp due d tang day ldn hon tfing mat trong ca pha tridu Ien va trieu xudng (hinh 9).

a) Pha tn

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Md hinh toan 3 chidu Delft 3D la mdt cdng eu manh cd thd md phdng tdt cfic qua trinh thuy dpng luc ddng chay va van chuyen biin cat, tram tich d khu vuc ciia song ven bidn. Kdt qua nghien cim cu the cho khu vue ven bidn Dd San - Hai Phdng da lam rd ca chd tuang tac dpng luc giiia ddng chfiy trong sdng, ngoai bien, md phdng dugc cac qua trinh van chuydn bim cat, hudng lan truydn va phan bd do due trong khu vuc. Trdn co sd cac kdt qua nghien ciiu cua md hinh, ed the dua ra cac giai phap cdng trinh phii hpp nhfim dieu chinh hudng van chuydn bim cat, lan truyen dp due tir cae cita sdng ra xa eae bai tam cua khu du lich Dd San de gop phfin cai thien hidn tugng nudc due d cac khu vuc nay.

Ldi cdm ffn

Noi dung cua bdi bdo Id mot phdn kit qud nghien ciru cua de tdi cdp nhd nuac "Nghien ciru ca sa khoa hoc vd de xudt cdc gidi phdp nhdm cdi thien hien tuang nuac due a viing bien Bo San, thdnh pho Hdi Phong" (md s6 KC08.34/H-15) do Phong thi nghiem trong diem quoc gia ve dong luc hoc song bien (Vien Khoa hoc thuy lai VietNam) thuc Men ndm 2014-2015.

Chung toi xin trdn trong cdm an Bo Khoa hoc vd Cong nghe dd tdi tra ldnh phi de thuc hien nghien ami ndy.

Tai lieu tham khao

[1] Ho Viet Cuang v^ cs, de tai cap nha mi6c ICC08 34/11-15' Nghien cuu ca sa khoa hoc vd de xudt cdc gidi phdp nhdm cdi thien hien tupng nuac due d vung bien Do Son, thdnh pho Hdi Phong, Phong thi nghi?m trong diem quoc gia ve dong luc hpc song bien.

[2] Pham Hai An (2012), Tridn khai dng dung mo hinh ECOMSED linh todn vdn chuyen trdm tich la lung khu vuc cua song ven bien Hdi Phong, Luan van thac sy, Tmang Dai hpc Khoa hgc lir nhien, 80 tr.

[3] Tran Anh Tu (2012), Ddnh gid dpc tnmg trdm Itch la liing khu vtfc cua song ven bien Hdi Phong, Luan van thac sy, Trucmg Dai hgc Khoa hgc tu nhien, 59 tr

[4] Dinh Van LTU (2009), "Mo hinh van chuyen tram tich va bien dgng dja hinh day ap dung cho viing bien cua song cang Hai Phong", Tap chi Khoa hoc, Dai hoc Qu6c gia Ha Ngi, 25(1S), tr 133-139

[5] W.L Delft Hydraulics (1999), Delfl3D-FL0W User Manual Version 3 05. DelftSD-Waq User Manual Version 3.01. Delft3D-Part User Manual Version I 0, Delft, Netherlands

c) Thdi diem nu&c rdng d) Th&i diem nudc, Hinh 9: kit qud mo phong qud trinh ian truyin do due trong m

tai khu vuc cdc ciea sdng vd vung ven bien khu vuc nghien

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