Tgp chi Khoa hgc Truang Dgi hoc Cdn Tho Phdn A: Khoa hgc Tu nhien, Cong nghe vd Moi tmdng: 31 (2014): 8-17
Tap chl Khoa hoc Tru'dng Dai hpc Can Thd website: sj.ctu.edu.vn
tTNG DUNG MO HINH THUY LU*C HAI CHIEU IMO P H 6 N G B ^ C TINH THUY Lire VA TINH TOAN BOI X O I 6 VUNG CITA SONG DINH AN Nguyin Phuong Tan', Van Pham Dang Tri^ va Vo Quoc Thanh'
' Khoa Moi truang & Tdi nguyen Thiin nhien, Truang Dgi hgc Cdn Tha Thong tin chung:
Ngaynhdn: 22/10/2013 Ngdy chdp nhdn: 28/04/2014 Title:
The application ofa two- dimensional hydraulic model to simulate the hydraulic properties and deposition and erosion patterns in the Dinh An estuary
Tir khda:
Boi ldng, xoi Id, cira song, mo hinh thuy lire hai chieu (CCHE2D). Ddng bdng song Ciru Long
Keywords:
Deposition, erosion, river mouth, two-dimensional hydraulic model (CCHE2D).
and Vietnamese Mekong Delta
ABSTRACT
In the recent years, estuary deposition and erosion due to hydrodynamics changes are amongst the major problems of the Dinh An estuary, one oj the two river mouths of the Hau River in the Vietnamese Mekong Delta.
Such natural phenomena are projected to be even greater in terms oj magnitude and unpredictable in terms of lime and space due to (i) the construction and operation ofhydropower dams in the upstream section oj the Mekong River, leading to changes of flow regime and sedimentation patterns along the river; (ii) on-going and planned hydraulic construction projects to meet different water requirements for agricultural land uses along the Mekong Basin, especially In the delta: and (iii) tidal regime changes in the East Sea. In this study, a two-dimensional hydraulic model (CCHE2D) is used to study the hydrodynamics, deposition and erosion patterns in the Dinh An estuary. The hydraulic component of the model is calibrated and validated based on the flows measured in August 2012. The sediment transport component is applied based on the calculated hydraulic properties and referenced sediment data (including suspended sediment concentration and transport sediment rate). The results obtained jrom this study set a stage for subsequent studies to understand the morphological changes of the river mouths in the Mekong Delta.
TOM TAT
Trong nhirng ndm gdn day, bdi ldng vd xdi Id Id nhirng vdn di chinh cdn dugc quan tdm a cua song Djnh An, mgt trong hai cua sdng cua sdng Hgu a Ddng bdng song Ciru Long. Qud trinh tu nhien ndy dugc du bdo se nghiem trgng han vd khd cd the du dodn dirge trong lucmg lai do: (i) qud trinh xdy d^g vd van hdnh cdc dgp thuy diin d thugng ngudn sdng Mekong, ddn din thay ddi cua che do dong chdy vd van chuyin bim cdi dgc ddng song; (li) cdc cdng trinh thuy lgi dang dugc xdy dung vd quy hogch de phuc vyi sdn xudt nong nghidp iren todn luu vuc sdng Mekong, dgc biit Id a viing dong bdng; vd, (iii) thay doi ciia dgng thdi thuy triiu biin Ddng. Trong nghien cuu ndy, md hinh thuy l^c hai chieu (CCHE2D) dugc sir dung dixdc djnh dgng thai ddng chdy, bdi ldng vd xdi la d cira sdng Dinh An. Thdnh phdn thuy luc cua md hinh dugc hieu chinh vd kiim dinh di^a trin sd ligu do dgc vdo thdng 8 ndm 2012;
thdnh phdn van chuyin biin cat ciia md hinh dugc tinh todn dua vdo cdc dgc tinh thuy luc vd sd lieu biin edt tham khdo tir cdc bdi bdo (bao gom: ndng dg bim edt la lirng vd van chuyin biin cat ddy sdng). Kit qud thu dugc tir nghien ciru ndy se tgo tiin di cho cdc nghien ciru tiip theo di tinh todn su thay ddi dja mgo ddy sdng cho cdc hg thdng cua sdng a Ddng bdng sdng Cuu Long.
Tgp chi Khoa hgc Trudng Dai hgc Can Tha Phdn A: Khoa hgc Tif nhien. Cong nghe vd Mditn/ong: 31 (2014): S-H 1 G I 0 I THIEU
Ddi^ bdng sdng Ciiu Long (DBSCL) (Hinh I A) Id vung ha luu cudi ciing ciia sdng Mekong trudc khi dd ra biln Ddng. DBSCL dugc xem li viing canh tic ndng ngfailp vd nudi frdng tfaiiy sin Ion nfait Viet Nam vd Id kfau v^fc quan frpng ddng gdp (faon 50% sdn lugng luong tfayc vd kfaoing 70% sin lugng thiiy san) cho sy phat triln kinh t i - xa hdi chung ciia Vi?t Nam (Trinh Cdng Vdn, 2009),
Sdng Hau l i mdt frong hai pfadn luu ciia sdng Mekong. Trudc khi dd ra biin Ddng, sdng Hiu chia thanfa faai nfainfa: Dinh An vd Trin Dl (Hinfa IB). Ciia sdng Dinh An Id mgt frong faai ciia sdng giii vm frd quan frpng frong phit friin kinh ti - xa hpi d viing bdn ddo Ca Mau {Hoa Manh Hung et ai, 2008). Tuy nhiin, frong nhOng ndm gdn ddy vung ciia sdng Dinh An thudng xuyln xdy ra qud frinfa bdi ling, xdi Id, va xdm nhgp man (Biii Hdng Long & Tdng Phudc Hodng Son, 2003; Hoa Manh Himg et al., 2008). Theo kit qui nghiin ciiu tir dnh
ve tinfa tti ndm 1989 - 2001, ciia Dinh An xdi Id kfaoing 4.5 m/nira vd bdi ldng kfaodng 9.5 m/nim (Huih IB) (Nguyin Viet Thanh etal., 2011). Trong tuong lai gin, sy gia tang cdc faoat dgng phdt triin d cdc nudc thugng ngudn (vi dy: vile gia tang lay nudc phyc vu cfao ndng ngfailp d vung Ddng Bdc Tfadi Lan, dy kiin xdy dyng cic dap frln ddng cfainfa sdng Mekong thudc Lao vd Campuchia) dugc dy bdo se lira tfaay ddi dang kl chi dd ddng chdy frln he thing cdc nhdnh sdng d DBSCL. Bin canh dd, do inh hudng cua bien ddi kfai fadu loan ciu nin nudc biln cd tfae ding lln thira khodng 23- 27 era vdo nam 2050 theo kich bin trung binfa (B2) (Bing I) (Bd Tdi nguyen vd Mdi trudng, 2012).
Cfainh vi the, vile tim failu ddng thai ddng chiy vi xdc dinh xu hudng bdi lang. xdi Id Id cin cii quan frpng de ddnh gii tinfa dn dinfa ciia fa? thdng sdng ciing nhu gdp phan gidi thich dgng thii ngudn tai nguyin nude mdt frln he thdng ddng sdng (dudi tdc dOng ciia sy thay ddi cua ddng chdy thugng ngudn vd ddng thdi thuy frilu) nham dim bao sy phit trien bin viing ciia viing.
Hinfa 1: Vftng ngfailn cihi - doan cira song Djnh An (cdch ciia bien khoang 7 km) Bang 1: M\rc niro'c bien dang (cm) it cac kich ban (Bg Tai nguyin va Mdi trudng, 2012) Kjch ban
Thap(Bl) Trung binh (B2) Cao(AIFl)
2020 8-9 8-9 8-9
2030 11-13 12-14 13-14
Cac moc thM gian ciia the kv 2040
17-19 17-20 19-21
2050 22-26 23-27 26-30
2060 28-34 30-35 35-41
2070 34-42 37-44 45-53
21 2080 40-50 44-54 56-68
2090 46-59 51-64 68-83
2100 51-66 59-75 85-105 Ngdy nay, vdi sy tiln bd cda khoa hgc rady tinfa
cung vdi sy pfadt triin eiia ky tfauat tinh toin faien dgi, cic md hinfa toin tiiiiy lyc mpt efaiiu (ID) da dugc xiy dyng vd img dung kfad nhiiu frong viec tim bilu dpng thai thiiy lyc ddng chdy d DBSCL (Trdn Qudc Dat et ai, 2012; Vdn Pfagm Ding Tri et ai. 2013). Cdc md hinh thuy lyc ID hien nay chi
tiling lai d miic dd tinfa toin gii tri tfaiiy lyc trung binfa d timg mgt edt dugc dua vio tt'nfa todn frong md fainh nfaung khdng xit din ddng chay ngang nhu frong rao hinh thiiy lyc hai chilu (2D) vd ba chieu (3D) vi tfal chua phdn anfa ddy dii bdn cbdt ddng thii thuy lyc ddng chdy. Hon niia, he sd nhdm thiiy lyc dugc dp dung frong rad hinfa thuy lyc ID (thudng) khdng tfaay ddi frln mdt mat edt
Tgp chi Khoa bgc Tru&ng Dgi hgc Cdn Tho PhdnA: Khoahgc Tunhien. Cong nghf vd Moi Iruang 31 (2014). 8-17 (faodc ca dogn sdng rad pfadng) nfaung frln t h y c te
thi he sd nhdm thiiy luc thay d i i frln tting phdn dogn cua mat c i t ngang va dpe (theo c h i l u d d n g c h i y ) (Nguyin C i n h Cdm et al., 2007; Wilson &
Atkinson, 2007). D o do, viec xdc djnfa d o n g thai tfaiiy lyc dong cfaay v i s y tfaay ddi fainh thai ldng sdng I i qud frinh phiic tgp frong h e thdng sdng/klnh t y nhien vd can cd s y fad frg ciia cdc md hinh loan tiiich h ; ^ (Wu, 2007).
Md hinh thuy lyc 2 D vd 3 D m d phdng chi tilt hon v l s y thay ddi ddng thai tfauy luc ddng cfaay cung nhu cd tfal ddnh gid sy thay ddi hinh thai ciia mdt dogn sdng (Wu, 2007). Tuy nhien, do han c h e cua cdc so lieu d u g c thu thgp tfaeo chieu thang diing (tir mat nudc xudng day sdng), m o hinfa thuy lyc 2D thuong dugc chap n h i n frong ngfailn ciiu (thay vl sii dyng md hinli thiiy lyc 3D) (Jia &
Wang, 1999). Do vdy, viec iing dyng m o hinfa thiiy lyc 2D nlidm xdc dinh dpng thdi thiiy lyc ddng c h i y , xu hudng bdi l i n g va xdi Id d v u n g ciia sdng d DBSCL la c i n thilt, d i e b i l l I i frong bdi canh cd sy thay d6i dang k l cua d i l u k i l n thiiy van t y nhiin, tinh hinh p h i t triln d thupng nguon luu vuc s6ng Mekong vd nudc b i i n dang. Hien nay, mdt s i m6 hinh thiiy lyc cd k h i n i n g tinh loan md pfadng
TdaadH
Jtffi,^^^i»?
^ ^
van cfauyin bun c i t va d y b i o s y tfaay ddi hinh tiidi sdng n h u : C C H E 2 D , DeIft2I>-River, M I K E 2 1 C , T A B S - M D vd T E L E M A C .
2 P H U ' a N G P H A P N G H I E N C U t J 2.1 K h a o s a t t h u e dia
T h i i t bi do dgc day sdng ky thugt sd A I X P (Acoustic Doppler Current Profiler), thilt bj cdra iing (sensor) v i h | t h i n g dirtii vi todn cdu (Global Position System - G P S ) d u g c sii d y n g frong c h u y i n di tiiyc dja tir n g i y 23/8/2012 d i n ngdy 31/8/2012.
Thiet bj A D C P d u g c d u n g de do dac edt Idp ddng chay bang sdng hoi i m theo hi$u iing Doppler.
TTiiet bj nay d u g c gan phia ben ngodi than tdu (Hinh 2A) v i d u g c k i t ndi vdl may tinfa de ghi nhgn Igi gia frj luu lugng vd c a o trinh cpt n u d c tgi cac mat cat, ciing nfau van tdc d d n g cfady. T h i i t hi cdm ling (sensor) diing dk d o gid frj m y c n u d c ddu vdo v i gid fri m y c n u d c dimg de kiem djnh md hinh. G P S d u g c diing d l xac djnh vj fri tgi diera do d a c vd d i i m xdi Id b d (Hinh 2B). Dii li^u do dgc tir A D C P se d u g c xii 1^ tir p h i n raira Winriver 11 vdi k i t q u a cd d u g c bao gdra lim lupng, dp sau, vd van toe ddng chay cho t u n g m i l c i t (Teledyne R D Instrument, 2007).
H i n h 2: T a u k h a o sat v a c a c t h i l t bi d o dgc ( A ) ; s a c djnfa vj t r i xdi Id * g a n ciia sdng (B) 2.2 M o h i n h t h u y l u c 2 chieu C C H E 2 D
M d hinfa tiiiiy lyc C C H E 2 D (cd kha ndng rad phdng ddc tinh tfaiiy ddng lyc fapc hai efaiiu (Langendoen, 2001)) d u g c sii dung frong ngfailn cihi n i y . M d hinh ndy d u g c tnrdng dgi hpc cdng ngh? Mississippi phdt friln nhira md phdng qud frinh fruyin tiiuj lye, cbdt lugng n u d c , van c h u y i n
bun c i t va b i i n ddng Idng ddn. M d hinh s d m 3 hon 1 MShinh ,s I
p h i n (module) chinh sau (Hinh 3 ) : | , c c « z . , • • „ . . . . , „ . . » , | H i n h 3 : T h a n h p h a n ciia m a h i n h C C H E 2 D
Tgp chi Khoa hgc Tnrdng Dgi hgc Cdn Tha Phdn A: Khoa hgc Tunhien. Cong nghi vd Moi Iru&ng: 31 (2014): 8-17 Md hinh tao ludi (CCHE2D Mesfa fainfa vi sd lilu do dac.
Generator): tao ludi gia tri fren h | tpa dp cong.
- Md hinfa sd (CCHE2D Numerical model):
tinh loan qui frinfa tfaiiy luc.
Md fautii giao diln dd fapa (CCHE2D- GUI Graphical Users Infreface); nhgp cdc tfadng sd md
Phuang trinh d^ng lugng theo phucmg x (Hinfa 4) (PT2):
dt^ dx^ dy ^ ax'^ h\ dx dy ) Phuong frinh ddng lugng theo phuong y (Hinh 4) (PT3):
•a(/ii
Cao dp myc nudc ty do dugc tinfa todn bdi phuang trinh liln tyc (PTI):
a^ d{uK) dQiv) at"*" dx "*" dy
7 + fco
( P T I )
- - + 1 / — + 1 ; -) ^ a(hlyy)\
dy ^CorU
(PT2)
(PT3)
Hinh 4: Hudng ddng cfaay theo hai phuong x, y Md hinh CCHE2D linh toin van chuyin biin cit frong hai Idp: ldp biin edt phia fren (ldp mdt) vd
ldp bun cat diy phia dudi; trong dd, ddng biin cit fren cfaiim fadu nhu toin bd dp sdu ddng chdy fa vd ddng biin edt nim 6 ldp diy cd bi ddy khd nhd.
Trong dd TJ : eao dp myc nuoc (m); t: thdi gian (s); fa: d0 sau cot nudc (m); u,v : van tdc frung binh theo hai phuong x vi y (ni/s); fr: he sd ma sat ddy;
fCor: thdng sd Corilolis; T;^;^, z^y, Ty^, Tyyi iing suit Reynolds (N/m^); vkTij^, Ti,y'. iing suit tilp tuyln diy (N/m^).
dz
Phucmg trinh truyin tii biin cat la Iiing cd dang sau (PT5):
^C^]+iimh-S)C^]+-^mh-S)C^]=j^[£,(^h-
( l - p ' ) ^ + - Pfauong frinli liln tyc vdt chdt day (PT6):
Trong dd: Cjt: ndng dp bun cat (kg/m^); u,v: van tdc trung binh theo hai phuong x vi y (ni/s); E^: he sd khulch tan rdi ciia biin cat (ra^/s); 5: he diy ldp biin cit diy (m); £>{,](: lugng trim ticfa bdi Idng;
Fjifc: lugng trim tich xdi Id; p ' : dp rong (%); c ^ : ndng dp trung binh cua bim edt tai ddy (kg/m^); va, QbkxiRbky- thdnh phan chuyen tdi biin cat theo phuang X, y (kg/s/m) (Wu, 2001).
3<lbky _
(PT5)
(PT6)
2.3 Pfammg pfaip giai cac phinnig trinfa trong md hinh CCHE2D
Cdc phucmg frinh frln dugc giil bang phucmg phip phin tii huu hiiu (Efficient Element Method);
diy li phuong phdp phan tir hiiu han ddc bilt, vd he phucmg frinh dugc giii frong he tpa do cong (^, TJ), ling vdi ludi cong tinh todn cua mien thye.
Hinh 5: Ludi cong xen ke trong tinh toan u, v, z (A); vj tri tinh todn thanh phan van toe va mure nu&c trong ludi ti'nh (B)
Tap chi Khoa hgc Truang Dgi hgc Cdn Tho Phdn A: Khoa hgc TV nhiin. Cong ngh4 vd Moi tru&ng. 31 (2014): 8-17 Trong ludi cong miln tinh, cdc thdnh phdn van
tdc dugc gidi tir phucmg trinh dpng lupng bing phuang phdp sai phin hiiu hgn so dd dn 9 mil theo khdng gian vd myc nudc dugc giii tir phuong trinh liln tyc trin phdn Ui Hen ket 4 diim (Hinh A).
Trong ludi cong tinh todn, tfaanh phan van tdc dugc bd tri tgi niit ludi vd myc nudc dugc bd tri tgi tdm d ludi (Huih B).
2,4 Thanh lap md hinh
Ludi tinfa: ludi tinfa dugc tgo tfaanfa bao gdm 9.000 nut (node) phin bd dpe miln ludi tinh (bao gdra: 30 d dpe theo hudng ddng chdy va 300 o vudng gdc vdi hudng ddng chdy).
Cao dp ddy: phuang phdp ndi suy tam gidc (Triangulation interpolation) dugc dp dung frong nghiin ciiu vi cao trinh ddy sdng ndi suy dugc xac dinh gdn vdi gid frj thyc do.
Diiu kiln biln tinfa toin thOy lyc: biln trin la chudi gid fri luu lugng (Q) thyc do vi biln dudi la chuoi gia frj rayc nudc (Z) thyc do (trong kfaodng thdi gian lir 9 gid ngiy 30/8/2012 din 3 gid ngdy 31/8/2012).
Dieu kiln biln tinh toin bdi ldng vd xdi Id tgi biln dau vao:
Ning dp bim edt dugc ging Id 0.25 kg/m3 vi thdnh phdn cic hat bim edt lo liing dugc xdc dinfa nhu frong Bdng 2 (Wolanski et al., 1996);
Bim cat van chuyin ddy la 0.034 kg/m/s vd
phdn cic hat biin cit ddy sdng dugc xdc djnh nfau frong Bing 3 (Albers & Lieberman, 2011; Nguyen Viet Thanh et al, 2011; Wolanski et al, 1996); vd
Thdnfa phdn radu biin edt vd dp rSng dugc xic dinh nfau Bing 4 (Rijn, 1993; Zou Xue et al, 2010).
Budc thai gian: Budc thdi gian dugc chpn frong tinh todn Id 60 gidy, thiit lip thdi gian xuat kit qud tgi dllm quan sdt Id 1 gid dk so sdnfa vdi kit qud tfayc do tai diem quan sdt.
Bdng 2: Thanh phan biin cat lo Itrng Kich Tfaudc (mm) Thanh phin ph^n trdm (%)^
0.00100 25 0.00425 75 0.12500 0 Bang 3: Thanh ph^a bim cit ddy song
Kich Thudc (mm) Thdnh ph^n pfa^n trSm (%) 0 0 100 0.00100
0.00425 0.12500
Bang 4: Thdnfa phan mau biln cat Kicfa thudc Thanfa phan _ . >
(mm) phin tram (%) ^ ^ ^^"^
0,00100 0.00425 0.12500
24,03
48.26 0.8 27.71
Hinh 6: Ludi, bien, cao dp ddy song, mgt edt
Tgp chi Khoa hgc Tnt&ng Dgi hgc Can Tho Phdn A: Khoa hgc Tu nhiin, Cdng ngh^ vd Moi iru&ng: 31 (7014): 8-17 2.S Hif u c h i n h va kiem d i n h md hinfa
Tinfa toin tfaiiy lyc: md fainfa dugc faieu cfainh bang cdch thay ddi he sd nhdm thi^ lyc Manning's n dya vdo dd siu cpt nudc. HI sd nhim thiiy lyc ciia sdng/klnh ty nfailn tten nen pfau sa d viing ddng bang dugc xdc dinfa ndm frong kfaoang 0.02- 0.05 (Chow, 1959). Dya vdo kfaoing gid fri nay. fa|
so nfadm tfaiiy lyc dugc tfaay ddi thdng qua phuong phdp tiiOr sai (Phgm Thi Bdo, 2009) cho din kfai tira ra he sd nhira thiefa hgp cho qud frinfa rad pfadng (gid tri md pfadng gin bdng gid tri tfayc do).
He sd nhim thiiy lyc dugc tt'nh phuang pfadp gidm ddn tfaeo chieu sdu cpt nudc (Picado et al, 2010);
frong do, (i) tai mil ludi cd dp sau cpt nudc rtiid nfadt (limin) se cd h | so nfadra tfaiiy lyc Idn nhdt (nmax); (ii) tgi mit ludi cd dd siu cpt nudc ldn nfaat (famax) sl cd h? sd nhira tfaiiy lyc nfad nfait (nmin);
va, (iii) cic vj fri kfadc hp sd nhdm thuy lyc se tfaay ddi tuyin tinh tiing budc (Wendt, 2008) theo edt nudc frong gidi hgn [nmin tdi nmax] (PT 7).
ni = n„.„ + ( n ^ , , - n j ( j ; ^ = ^ ) (PT7) Trong dd: n,: he sd nham thuy lyc tai nut i (s/m"^); nmin, nmax: he sd nhim thiiy luc Idn nhit va nhd nhit (slm^'^); (hmm) vd (famax): dp sau edt nudc ldn nhdt vi nhd nhdt (m); vd, fa,: dp siu cpt nudc tai mil tfaii i (m).
Sau khi hi|u chinli, md hinfa dugc kiim djnh bdng gid ui myc nudc do dac tir 9 gid 30 phut ngiy 30/8/2012 din 3 gid 30 phiit ngiy 31/8/2012.
Phuang phap kilm djnfa nay dya fren nin tang cua vile iing dung md fainfa kilra dinh ndi tai (internal validation) (Shading et al, 2002).
Tinh todn xdi Id: frong rad hinh bdi xdi d ciia sdng Djnfa An, 3 fae sd can quan tara bao gdra: he sd phii hgp ciia biin cat lo Iiing a, dp rdng ciia mlu bun cdt/r' va chilu dai ludi tinfa phu hgp ciia bim edt day sdng Z,,; frong dd, chieu dai ludi tuih dugc tfnh nhu sau (PT8) (Qamar & Baig, 2012):
ts = 3dsoD?-^T°-^ = 32.644 (m) (PT8) Trong dd:
Tfc _ O.OSpgdso 'T, 0.047 * ( y , - K ) d 5 - = 0.671
D. = dsi pu^ J 3,110.804
Trong do: Ls: chilu dii d ludi tinh phii hgp (m);
dsoi kicfa thudc trung binh ciia hat bim cat day sdng (ram); pf. ^ frpng ciia bim cat (kg/m^); p: t\- frpng ciia nudc (kg/m^); y^: frpng lugng riing ciia bim edt (N/m^); vd, y: frpng lugng rieng eiia nudc (N/m^.
Wu vi Li (1992) dl nghj ring he sd pfaii fagp cua bun edt la liing: or=I cfao trudng fagp xdi Id ragnfa; a=0.25 cho truong fagp Idng dpng manh; vd, 0=0.5 cho tnrdng hgp bdi ldng vd xdi Id ylu. Do khu vyc ha luu sdng Hdu tfaudng xdy ra qud frinfa bdi ling (Nguyen Van Lap et al, 2000; Zuo Xue et al, 2012) nin he sd a=0.25 dugc lya cfapn de tinh todn qua trinh bdi Idng vd xdi Id.
Theo ngfailn ciiu cua Xue et al. (2010) biin cat to lung d ciia song Djnh An cd dg rong cao vd thdnh pfain bun edt cfau yeu Id set, biin vi c i t Sy bdi ldng ciia cac thdnfa phdn bun cat fren cd dp rdng khoing 0.8 (Rijn, 1993); do do, trong md hinh ndy, gii trj dp rdng (bing) 0.8 dugc dp dyng.
Trong dilu kiln gidi hgn ve sd lieu de failu chinh vd kilm djnh md fainh, bin cgnh viec so sdnfa giiia sd lieu myc nudc rad pfadng vi muc nudc tfayc do de kilm cfaimg tinh phu hpp eua md hinh ve khia canh thuy lyc, kit qud md phdng bdi / xdi bd sdng ciia mo fainh cdn dya vdo dilu kiln khao sat tfayc tl ngoii ddng.
3 KET QUA VA THAO LU^N 3.1 Kit qua tinfa todn thiiy luc Mo hinfa dugc faieu ehinh thdng qua viec tfaay ddi fae sd nhdm thiiy lyc Manning's n; vdi he sd nhim thuy lyc ndm frong khoing 0.018-0.030 (s/m"^), kit qua myc nudc md phdng tgi diem quan sdt phu hgp vdi kit qui thyc do (Hinfa 7 A) (he sd Nash Sutcliffe NS = 0.97). Ngodi ra, he sd nhdm dugc ip dyng frong md hinh pfaii hgp vdi he sd nhdm trong ngfailn ciiu trudc ddy cua Trin Qudc Dat, et al (2012) vd Ldm MJ Phyng et al (2013), Ben canfa dd, md fainfa ciing dd dugc kiem djnfa (Hinfa 7 B) (he sd Nash Sutcliffe NS=0.98); diiu nay cho tfaiy md fainfa cd tfal dugc sii dung de md phdng dpng thdi tfauy lye ddng chiy tten nfainfa sdng n ^ i l n ciiu.
Tgp chi Khoa hgc Truang Dgi hgc Cdn Tha Phdn A: Khoa hgc TV nhien, Cong nghi vd Mdi tniong: 31 (2014): 8-17
•Tliiicdo • • • • Mophoug Hinh 7: Myc nudc thyc do vi md phdng tai diem quan sdt
Van tdc ddng chdy tai mat edt 2 (Hinfa 6) dat gii tri ldn nhit tgi thdi diem 18 gid (Hinh 8 A) vi dat gid frj nfad nhit tgi tfadi diira 22 gio (Hinh 8 B);
kit qud ndy pfaii hgp nghiin ciiu cua Lane et al.
(1999) - vin toe ddng chdy fren mdt mdt edt ngang
^4 5 ' 0 6 Khoinzcadidii) , 0
ting ddn tfaeo do sdu. Ngoai ra, do dogn sdng nghien ciiu tuong ddi thing nin myc nudc frln timg phan doan cua mdt mil edt khdng cd sy chinh lech ddng ki (Huih 9).
K]ioaugcacfa(iu)
Viiitocdonzcruy Caododay.-oti2« • • • Van toe dong diay Hinh 8: Van toe ddng chay tai mat c3t 2 tgi thdi diem 18 gid (A) va 20 gid (B)
-0 928 Kho.iiiKc.-ich(ni)
- Cao dij day sons •0 940
• • • Myc nuoc
Khoang each (m)
~ Cao dp day sons Hinh 9: Muc nu*c tgi mdt edt 2 tgi thdi diim 18 gid (A) vd 20 gid (B) 3.2 Ket qua tinh toan bdi ldng vd xdi Id*
Klt qud tinh todn boi ling vi xdi Id tgi mgt edt 1 (Hinfa 6) cho tiidy sau tiidi gian md phdng eo sy
la 8.5 X 10-6m (Hinh 10 B), vd bdi ldng d bd Tri Vinh la 2.1 x 10-5m (Hinfa 10 B).
xdi Id bd Cii Lao Dung cu tiii Id 1.9 x 10-6 m (Hinh 10 A), xdi Id d bd Cii Lao Dung tai mit edt 3
Sy xdi Id bd frai tgi faai vj fri (mgt edt I vi 3) phil hgp vdi vj fri xdc djnfa xdi Id bd frong chuyin khao sdt thyc dja (Hutii 2 B). Xu hudng bdi Idng
Tgp chi Khoa hgc Tru&ng Dgi hgc Cdn Tha Pkdn A: Khoa hgc Tu nhien. Cong nghf vd Mdi tnr&ng: 31 <20!4i: S-1' gin ciia sdi^ tai m|it edt sd 3 phii hgp vdi kit qui cat dugc liy dpe bd sdng van cfauyen ra vung ciia ngfailn eiiu trudc ddy ciia Xue et al. (2012) vl bun sdng va bdi lang tai ddy.
- • • -1.5E-06S- = -1< H F -
Bo CM U o Dims: -2 .OE-06 -20 BoO'iLaoDniix - -2.0E-05
Hinh 10: Thay ddi ddy song sau thai gian md pfadng Trong phdn Idn tfadi gian md pfadng, faudng
ddng cfady d mat edt 1 (Hinh II A) vd mat edt 3 (Hinh 11 B) ludn hudng vio bd Cii Lao Dung - diy
A 0.40 ~ 020 1 :
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*HiiO]isvaul6cdoua:cliay B O C I D Hinh 11: Hudng van tdc dong cfaay d mat cat 1(A) va 2 (B) tai bdCu Lao Dung Van tdc dong chdy tai mat edt so 1 (Hinfa 12 A) van tdc ddng cfaay tai mat edt sd 3 (Hinfa 12 B) tgi faudng vdo bd Trd Vinfa (TV) nfaieu faon so vdi pfaia bd Tra Vinh cd hudng ddng chiy vio bd Trd hudng ra giiia sdng, Tuy nhien, vgn tdc hudng vao Vinh rdt it - ddy cd till Id nguyin nhdn giy ra bdi bd rit nhd nen kfadng tfal ldm xdi Id bd Tri Vinfa; Idng d vj tri ndy.
.4
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*Hnoiisvan loc douz diav Hinh 12: HuAng van toe dong chay a mat cit 1(A) va 2 (B) tai b * tai b * Tra Vinh
Tgp chi Khoa hgc Tntang Dgi hgc Cdn Tho Phdn A: Khoa hgc Tu nhiin. Cong ngbe vd Mdi ini&ng • SI (2014)-8-17
4 KETLU^N
Bdi ldng v i xdi Id Id tinfa frang chung cda cic cira sdng ven biin DBSCL vdi quy md khdng gian va thdi gian khic nhau. Ket qui tinh todn cho thiy viing ciia sdng Djnh An cd xu faudng xdi Id dpe bd Cii Lao Dung.
Kit qud nghiin ciiu cho tiidy md hinh thiiy lyc hai chiiu (CCHE2D) cd tiii md phdng dpng thdi thiiy lyc dong chay frln dogn sdng ngfaien ciiu vdi dp tin ciy cao, cd friin vpng iing dyng nghiin ciin tren he thing cdc nhdnh sdng d DBSCL. Tuy nhien, do han chi ve thdi gian va sd lieu do dac, nghiin ciiu nay chi dupe thyc hien nhim md phdng die tinh tiiiiy lyc ddng chiy (frln doan song nghiin cihi) trong thdi gian ngdn nin chua phin inh diy dii die tirJi thuy lyc ciing nhu sy thay ddi hinh thdi Idng sdng; mdc dii viy, kit qui nghien ciiu vdn cd thi chimg minh dugc sy biln ddng dja mgo viing cira sdng (phii hgp vdi kit qud ciia kliao sat thuc dia).
Hi|n nay, phdn ldn cac iing dung md fainh thiiy lyc d DBSCL cdn bj hgn chi ve mdt sd lieu (sd Ii?u do dac dd cii hoic khdng cd sd lilu thyc do). Trong bdi cdnh cd sy thay dii ldn vi luu lugng va hinh thii Idng sdng, vi^c ip dyng cdc thilt bj do dac hien dgi (nhu thiit bi ADCP, thilt bj do myc nudc bing sensor) di thu thgp cac so lieu thyc ti nhdm myc lilu phuc vy cho vi|c nghiin eiiu ddng thai dja mgo vi thiiy lyc la dieu cdn dugc quan tim.
TAI LIEU THAM KHAO 1. Albers, T., & Lieberraan, N. v. (2011).
Curent and Erosion Modelling Servey.
Deutsche Gesellschaft fur Internationale Zusaramenarbeit (GiZ) GmbH.73.
2. Bp Tai Ngu);lnva Mdi Trudng. (2012).
Kjch bin Biln ddi Khi hiu, Nudc bien ddng cho Viet Nam. Nfad xudt ban Tii nguyen- Moi tru&ng vd Ban do Viet Nam.84.
3. Biii Hdng Long, & Tdng Phudc Hoang Scm.(2003).Dic diera dja hinh vd biln dpng ludng Igch viing ciia sdng Dinh An.107-127.
4. Chow, V.T. (1959). Open Channel Hydraulics: Blackburn Press.700.
5. Hoa Manli Hiing, Nguyen Quang Thanh, &
Phan Thj Thanh Hdng. (2008). Ddng lyc phat friin viing ciia sdng Hdu (ciia Djnh An- Tranh Dl). Cic khoa hoc vi frdi dit, 30: 130-135.
6. Jia. Y., & Wang. S. S. Y. (1999). Numerical Model for Channel Flow and Morphological
Change Studies, Joumal of Hydraulic Engmeering, 125(9): 924-933.
7. Ldra My Phyng, Vdn Pham Ddng Tri, &
Trin Quoc Dat. (2013). tfng dyng md hinh toin thiiy lyc rapt chiiu ddnfa gii vd dy bdo tinh fainfa xdm nhgp min frln h | thdng sdng chinh fren dia ban tinh Tri Vinh. Tgp ehi Khoa hpc- Trudng Dai fapc Cdn Tho, 25 (2013): 68-75.
8. Lane, S. N., Bradbrook, K. F., Richards, K.
S., Biron, P. A., & Roy, A. G. (1999). The Application of Computational Fluid Dynamics to Natural River Channels:
Three-Dimensional Versus Two- Dimensional Approaches. Geomorphology, 29: 1-20.
9. Langendoen, E. L(200I).Evaluation of tiie effectiveness of selected computer models of depth-averaged free surface flow and sediment transport to predict the effects of hydraulic structures on river morphology.Project Report, USDA-ARS National Sedimentation Laboratory, Oxford M.S.
10. Nguyin Cdnh Cdm, Luu Cdng Dio, Nguyen Vdn Cung, Nguyin Nhu Khul, V6 Xuin Minli, Hoang Van Quy, & Vu Vin Tio.
(2007). Thuy Lyc Tip 2. Hd Npi Nhi Xuat Bdn Xay Dyng.323.
11. Nguyin Vdn Lap, Tg Thj Kim Cartii, &
Tateishi, M. (2000). Late Holocene Depositional Environments and Coastal Evolution of the Mekong River Delta, Southern Vietnam. Joumal of Asian Asian Earth Scienes, 18(2000): 427-439.
12. Nguyin Vipt Thanh, Hai, Z. J., & Hau, L. P.
(2011). Morphological evolution of navigation charmel in Dinh An estuary, Vietnam, River, Coast and Estuame Morphodynaraics: RCEM2011 Tsinghua Universl^ Press, Beijing.469-482.
13. Phgm Thi Bdo.(2009),Cic phuang phip giii quylt bai todn frln mdy tuih. Khoa Toin - Tin,Trudng Dai hpc Khoa hpc Ty nfailn.
14. Picado, A., Dias, J. M., & Fortunato, A. B.
(2010). Tidal Changes in Estuarine Systems Induced by Local Geomorpfaologic Modifications. Continental Sheft Reseach, 30(2010): 1854-1864.
15. Qamar, M. U., & Baig, F. (2012).
Calibration of CCHE2D for sediment simulation of Tarbela Reservoir.
Tgp chi Khoa hgc Tnt&ng Dgi hgc Cdn Tho Phdn A: Khoa hgc Tv nhien. Cong nghe vd Mdi tnr&ng: 31 (2014): 8-17 Proceedings o f tfae World Congress on
Enguieering 1:978-988.
16. Rijn. L. C. V. (1993). Principles of Sediment Transport ui Rivers, Estuaries and Coastal Seas. Tfae Netfaerlands: Universi^
of Utrecfat Department of Pfaysical Geography.700.
17. Shading, W. R„ Cook, T. D., & Campbell, D. T. (2002). Experimental and Quasi- Experimental Designs for Generilized Causal Inference Boston. Houghton Mifflin, Boston, New Yortk.
18. Teledyne RD Insttnment. (2007). Wmriver II User's Guide.
19. Trdn Qudc Dat, Nguyen Hiiu Trung, &
Likitdecharote, K. (2012). Md Pfadng Xdm Nhgp Man Ddng Bdng Sdng Ciiu Long Dudi Tac Dpng Myc Nudc Biln Ding Va Sy Suy Giira Luu Lugng Tir Thugng Ngudn. Tgp Chl Khoa Hpc, Trudng Dai Hpc c i n Tho, 21b: 141-150
20. Trjnh Cdng Vdn. (2009). Identification Of Sea Level Rise Irapacts on the Mekong Delta And Orientation Of Adaptation Activities. VieiNam National Commitee On Large Dams And Water Resousces Development. 1-6.
21. Vdn Pham Ddng Tri, Popescu, I., Griensven, A, v., Solomatine, D., Nguyin Hiiu Trang,
& Green, A. (2013). A Sttidy of tiie Climate Change Impacts on Fluvial Flood Propagation in the Vietnamese Mekong Delta, Hydrol. Eartii Syst, 9: 7227-7270.
22. Wendt, J. F, (2008), Computational Fluid Dynamics. 72 Chaussee de Waterloo B- 1640 Rhode- Saint- Genese: Belgium.299 23. Wilson, M. D., & Atidnson, P, M. (2007), The Use of Remotely Sensed Land Cover to Derive Floodplain Friction Coefficients for Flood Inundation Modelling. Hydrologieal Processes, 21(26): 3576-3586, 24. Wolanski, E., Nguyen Ngoc Huan, Le
Trong Dao, Nguyen Huu Nhan, & Nguyen Ngoc Thuy. (1996). Fme- sediraent Dynamic in the Mekong River Estuary, Viemam. Estuarine, Coastal and Shell Science,, 43: 565-582.
25. Wu, W. (2001). CCHE2D Sediment Transport Model, Scfaool of Engineering Tfae University of Mississippi.43.
26. Wu, W. (2007). Computational River Dynamics. Taylor & Francis, London 2007 27. Wu, W„ & Li, Y. (1992). One and two-
dimensional nesting model for river flow and sedimentation. Proc. 5tfa Int.Symp. on River Sediranet.
28. Xue, Z., He, R., Liu, i. P., & Wamer, i. C.
(2012). Modeling transport and deposition of the Mekong River sediraent. Continental Shelf Researcfa, 37(2012): 66-78.
29. Xue, Z., Liu, J. P., DeMaster, D., Lap, N.
v., & Oanh, T. T. K. (2010). Late Holocene Evolution oflhe Mekong Subaqueous Delta.
Southem Vletnara. Marine Geology, 18:
427-439.
