ufng dung mo hinh HEC-RAS
trong nghien cuU dong chay song Can Thof
O v o THj NGpC GIAU Cdng an quan Cai Rang, TP. Can Tha
PHAN THj BiCH TUYEN
Cdng ty TNHH va San xuat ThUdng mai Anh Tuan N G U Y I N HIEU TRUNG
Vidn Nghien eiiu Bien Doi khi hau, Trudng Dai hoc Can Tho TOM TAT
Md hinh toan thuy Ipe ddng vai trd quan trpng trong viee gia tang hl$u qua quan ly va ddnh gid ngudn tai nguyen nude (TNN). Cdng trinh khoa hpc dupe thpc hien vdi mye tieu la Ung dyng md hinh HEC-RAS trong nghien cUu dong chay song Can Tho. Nghien eUu nay si^ dyng phUdng phdp xay dung mo hinh thuy luc HEC-RAS ID vd 2D nham danh gia ehe do thuy Ipc, dia mao va kha nang khuech tdn edc chat 6 nhiim. Ngi dung eua de tai bao gom: (1) Npi suy cdc mat cat tren doan song Can Tho, (ii) hieu chinh dja mao sdng cho phu hpp vdi thuc te, (iii) phdn tich kha nang khuech tan eae chat d nhiim d mpt sd vi tri tren doan song Can Tho. Ket qua dau tien eua nghien eUu Id xdc dinh dupe nhUng mat cat song Can Tho da dupe ndi suy vd dieu chinh. Ket qua thUhai eija de tdi la ddnh gid dupe kha nang khuech tan ehat 6 nhiim eua song Can Tho.
Gidi thi$u
Can Thd la mdt trong nhQng thinh pho dUng dau ve phat trien kinh t l khu vUc Dong bang sdng CCfu Long. Do dd, thanh pho cung dong mdt vai trd quan trpng trong n i n kinh t l - xa hpi cua ca nude ndi chung v l cua khu vUc ndi rieng.
Nguin TNN ddng gdp mdt phan khdng the thiiu cho khu vUc ndi chung va Can Thd ndi rieng. Tuy nhien, nguon TNN hien nay da v l dang ngly cang trd nen nghiem trpng, dac biet I I nude mat ngay cing thoai hoa va mUe dp d nhilm nude ngly cang tang.
Vdi dieu kien khi hau nhiet ddi gid mua v l cd hai mua rd ret, dd la mua khd va mua mUa.
Hai mua nay Inh hudng rat nhieu
d i n nguon nUdc, die biet la che dp ddng chly cQng nhU lUu lUdng nude tren sdng. Theo Nguyen Thanh Sdn (2005), ddng thii cua ddng nUde dUpc dinh gia bdi su thay doi eija elc dac trung nude thed khdng gian va thdi gian. Do dd, su thay doi theo mua va dja mao cua sdng se lim thay doi c h i dp ddng chly, eung nhu thay doi ve lUu lUdng nude tren sdng.
De tai "Ung dyng mo hinh HEC-RAS trong nghien eUu ddng chay song Can Thd' dupe thuc hien tren cd sd sCf dung md hinh HEC-RAS. Nham gdp phan nang cad hieu qua sCf dyng TNN cung nhu viec quan ly tong hpp TNN cua vung Deng bing Sdng CQu Long ndi chung v l TP. C i n Thd ndi rieng.
PhUdng phap nghien cUu Ddnh gia ddng chay vd dja mao song
Bude 1: Md phong ddng chly thuy luc bing md hinh c i n cd:
Mat elt dja hinh; dilu kien bien;
dieu kien ban dau ddng chly. Bd thdng s i thuy lUe phu hpp.
Bude 2. Xle djnh c l e he so dia mao thiJy lUc v l ndi suy dd sau b l mat cCia doan sdng nghien eUu.
Budc 3: Sii dung md hinh HEC-RAS 2D danh gia md'i tUdng quan giQa dia mao thuy lUc va ehe dp thijy lUc trdn doan song va kha nang Inh hUdng den van d l mdi trudng.
Ket q u i va t h i o Iu3n Doan sdng Can Thd dupe xay dung tren HEC-RAS cd tpa dp tUdng Ung vdi doan sdng tren anh ve tinh, tU doan tiep giap giUa Tai nguyen va Moi trtfofng 9 0
Ky 1 - Thong 2/2020 ^^
song Can Thp vdi sdng Hau tgi vj tri so 5 (X:586604; Y:1109317) d i n vj tri so 1 (X: 578203;
Y:1104040). T i e g i i da tiln hanh chay md hinh HEC-RAS I D v l H EC-RAS 2D v l eho cac k i t q u i nhusau:
Doan sdng ed 5 mat eat chinh hinh 2.1 (mit cat 5, 4, 3, 2 va mat cat so 1). Doan song cd chieu dai hdn 11 km. Doan tQ vj tri mat eat 5 d i n vj tri 1 cd khoing c i c h 4,09 km, doan MC4 d i n MC3 khoang 2,22 km, dogn MC3 den MC2 ed chiiu dai 1,53 km v l doan con Igi (doan MC2 d i n IVIC1) cd chiiu dai khoing 4 km.
Trong hinh, sdng Can Thp vdi 5 mat cat ben trdn nhd cdng cu cua md hinh HEC-RAS 1D, ta cd the ndi suy ra dUdc nhieu mat cat khac nhau. Md hinh vdi phUdng phap ndi suy (Geometry data/Tools/XS Interpolation/ Within a Reach) ndi suy dupe 27 mat cat tu 5 mat eat cd s i n . Khoing eleh giQa eat mat eat npi suy nam trong khoing 350-500 m.
Ket qua ch^y md hinh HEC- RAS ID
Mat cat ndi suy d doan sdng thing va cong
Tai nhQng doan sdng thang thi k i t qua giQa dp sau mat cat Idng sdng ke Can Thd vdi dp sau mat c I t ndi suy khdng cd nhiiu khac biet Tai nhQng vj tri dean
giQa dd sau Idng sdng tgi khu vUc ke v l dp sau mat cat npi suy.
K i t q u i npi suy phu thupc vao elc thdng so nhU: So lupng do lieu; chl't lUdng dQ lieu; si;
phan bo eija dQ lieu trong khu vUe nghien cUu.
Kit qua hi$u ehinh edc mat eSt
Tac gia da t i l n hanh dilu chinh dd sau mat e l t ndi suy d khu vUc sdng ke Can Thd eho ket q u i tUdng dd'i phu hdp vdi dja mad khu vUc Idng sdng ke Can Thd. Dd dd, tac g i i da md rdng ra doi vdi toan dogn sdng Can Thd v l tilp tuc chgy md hinh HEC- RAS 2D.
Kit qua ehay md hinh HEC- RAS 2D
Sau khi hoan thanh viee dieu chinh npi suy cho toan doan sdng Can Thd. NhiJng mat cat dupe dilu chinh dUpc sQ dung lam nguon dau v i o eho md hinh HEC- RAS 2D. TU nhQng mat cat dUpe dieu chinh vdi cdng eu RAS MAP- PER trong md hinh 2D da tao ra dupe dja mao md phdng cho toin doan sdng khu vUe nghien cUu dua tren nhQng mat elt tren.
Md'i tUdng quan dia mao vdi vdn tdc ddng ehiy: Dia mgo ludn Inh hudng d i n van toe cua ddng chay v l van t i c cung lam anh hudng v l thay doi dja mao cua Idng sdng. Ket q u i 2 ben bd cua doan sdng tai nhQng vj tri sdng uon khue thi ed sU khae biet
Hinh 2: Doan song trong md hinh HEC-RAS va hinh dang 5 mat cit sdng Can Tho
doan cong se lam cho bj xdi Id nhieu hdn.
Canh bao chi't lupng nddc cho cac doan song cong
Qua ket q u i ehay mo hinh tai cle vj tri cong tren ddng sdng eho Khoanh vUng nhQng doan cong tren sdng Cin Tho td kd't qud md
hinh HEC-RAS 2D
kit luan ring: GiOa van toe ddng chly va dja mao Idng sdng cd moi quan he mat thiet vdi nhau. Ben eanh dd, v i n toe ddng chly cung Inh hudng khdng nhd den k h i nang x l o tron va khulch tan ehit 6 nhilm. Do dd, can cd bien phip quin lytoiuu, khdng chi tgi nguin diem x l thii ma nd cdn ton tgi tai nhQng khu vuc van toe ddng chly thap, ndi m l ehat d nhiem bj tu dpng lai. Vi t h i , can xem xet v l cd bien phip hdp ly khdng chi tren dogn sdng nay ma cdn md rdng cho nhQng doan sdng khae.
K i t qua eija nghien cUu cho thay, khi chgy md hinh 1D da tim ra dupe mat elt npi suy va x l e djnh dupe chiiu ddng chay tU sdng Hau chay vao sdng Can Thd. K i t q u i md hinh vdi he so tUdng quan R gan bang 1 cho thay md hinh dat hieu q u i vdi md phdng trUde. Nghien cUu da sc sanh dupe mat elt sdng ndi suy vdi mat c i t thuc t l khu vuc Idng sdng ke Can Thd. Kit qua da tim dupe khoang chenh lech AH va tinh dupe phan tram chenh lech so vdi thuc te. Doi vdi nhQng doan sdng edng phan tram chenh lech AH I110,7%, va nhOng doan sdng
^M Tai nguyen va Moi litftfnn
^^ Ky 1 - Thdng 2/2020
t h a n g thi phan tram chiem 1,7%. K i t qua Ung dung m d hinh H E C - R A S 2 D cho thay doi vdi nhOng vl tri cd d d sau cang Idn cho k i t q u i van toe cao ddng c h l y cang cao. Q u a md'i lien he giOa dja mao va v a n toe ddng c h l y s d n g nham giup c i n h bao v l kha nang ton luu chat d nhiem hoac k h i n a n g k h u l c h tan e l c chat trong m d i trudng nude. K i t q u i doi vdi nhOng doan eong tren c u n g mdt mat cat ngang 2 ben b d cd dp sau khac nhau, vj trf cc dd sau Idn tUdng quan vdi van td'c Idn thi k h i nang ehat d n h i l m se k h u l c h t i n xao tron t i t nen kha n a n g lam sgch m d i trudng tgi khu vuc d d tot. Ngupc lai, doi vdi b d doi dien c d dp sau mat e l t ngang eang thap thi k h i n a n g x a o trdn va khuech t i n chat d n h i l m c i n g thap d i n d i n chat d n h i l m dupe khuech t i n k e m . Do d d , vat c h a t d n h i l m d l bj tu d d n g va luu tru lgi 5 nhOng vj tri dd lau hdn va gay I n h h u d n g d i n chat lupng nguon nUdc va I n h hudng den sUc khoe edng d o n g khi sCfdung nguon nude,
K e t l u a n
S a u khi e h a y m d hinh I D , k i t q u i da tim ra dupe mat e l t ndi suy va xac djnh dUde ehieu d d n g c h l y t u s d n g H a u c h l y v a o s d n g C a n T h d . Ket qua m d hinh vdi he so tUdng q u a n R gan b a n g 1 eho t h a y m d hinh dat hieu q u a vdi m d p h d n g trUde.
Be tai da so s i n h dUdc m a t e l t s d n g ndi suy vdi mat eat t h u c te khu vuc Idng s d n g ke C a n T h d . K i t q u i tinh dUdc k h o i n g c h d n h lech AH va phan tram c h e n h lech so vdi t h u c t l . Dd'i v d i nhQng dogn s d n g cong phan tram chenh lech AH la 10,7%, va nhQng d o g n s d n g t h a n g thi p h a n t r a m c h i e m 1,7%. K i t q u a kiem tra tgi vi tri K T 2 2 d e n K T 1 3 d e u cho k i t qua phu h d p . Do d d , t o a n doan s d n g dUdc d i l u ehinh dUa v i o p h a n tram c h e n h lech n h u t r e n .
K i t q u i m d hinh H E C - R A S 2D cho thay dd'i vdi nhQng vj tri ed dp sau Idn hdn eho ket q u a v a n td'c cao h d n , eho k i t q u i phu hpp. Q u a m o i lien he giOa dia mao va v a n td'c ddng c h l y s d n g n h a m giup eanh b i o ve kha n a n g t o n lUu ehat d n h i e m h o l e k h i n a n g k h u e c h t i n e l e eha't trong m d i trUdng nude.
K i t q u a doi vdi nhOng d o g n eong tren c u n g mpt mat cat ngang 2 b e n b d ed dd s a u khae nhau, vi trf ed dp s a u Idn tUdng quan vdi v a n td'c Idn thi kha nang c h a t d n h i e m se k h u l c h tan x a o trdn td't nen kha n a n g lam s g c h m c i t r u d n g tai khu vuc d d td't. NgUpe Igi, doi vdi bd d l i dien cd dp s l u mat e l t ngang tha'p thi k h i n a n g x a o trdn va khueeh tan chat d n h i l m thap hdn d i n d i n chat d n h i l m khuech tan k e m . Do d d , vat c h l ' t d n h i l m d l bj tu d p n g v l luu tru lai d
nhQng vj tri d d lau hdn va gay I n h hUdng den ehat lupng nguon nude va sUc khde c d n g d o n g .
K i e n n g h j
Mdt trong nhQng y e u to can thiet dau tien c u a m d hinh toan la c a n thu thap cDng nhu do dgc day diJ so lieu de chay m d hinh H E C - R A S 1D va 2 D : So lieu ve m a t cat thuc do, luu lupng bien tren (theo tUng gid h o l e tUng ngay), muc nude bien dudi (tUng gid hoac tUng ngay); chat lupng nude cung thdi diem vdi luu lupng v l muc nude.
D e d i n h gia td't hdn ve thuy lue va c h l ' t lupng m d i t r u d n g nude d o a n s d n g C a n T h d c a n nghien cUu t h e m nhUng kenh rgch nho vi mdt phan d i n g ke luu l u p n g c u n g n h u c h l ' t lUpng nude cCia cac kenh rgch nho nay c h l y vao sdng C a n T h d .
T A I L I E U T H A M K H A O
1. N g u y i n T h a n h S d n , 2 0 0 5 . Danh gia TNN Viet Nam. Nha xuat ban giao due 2005;
2. Phan Thi San Ha, Le Minh S d n , 2 0 0 6 . (>hg dung phuang phap ngi suy Kriging khaa sat sd phan bd cua tang dat yeu tuoi Holoeene khu vuc noi thanh TP. Ho Chi Minh. Science & Technology Development. Vol 10. No.02 - 2007;
3. T d T h u y Nga, 2 0 1 1 . Ap dung md hinh MIKE 11 va HEC-RAS tinh cho bai toan truySn lu tren sdng Bung 4. T a p chf Khoa hoe edng nghe D a i hpe D I N a n g . 3(44):81-89;
4 F.E. Hicks. T. P., 2005. "SL//faM/Vo/HEC-R/^S for Flood Forecasting."Canadian Water Resources Journal 30(2): 159-174;
5. Gary W. Brunner, H E C . 2014. Combined ID and 2D Modeling with HEC-RAS;
6. H E C , 2010. HEC-RAS River Analysis System:
User's Manual available at http://www.hec.usace.army.
mil/software/hee-ras/ index, html;
7. Lane. S. N. Bradbrook K. F., Richards. K. S., Biron. P. A. & Roy. A. G. (1999). The Application of Computation^ Fluid Dynamics to Nahjra} River Channels:
Three-Dimensional Versus Two Dimensional Approaches.
Geomorphology. 29: 1-20. 9. Langendoen. E;
8. Mate Kardos, 2012. Interpolating river's morphological model from cross sectional survey Second Conference of Junior Researchers in Civil Engineering;
9. Morant River: Hydraulic Geometry & Fluvial Hydraulics, http://sehoolwarkhelper.net/morant-river- hydraulle-geometry-fluvlal-hydraulies. Truy cap ngay 4/8/2015;
10. fvlueller, Jerry (1968). "An Introduction to the Hydraulic and Topographic Sinuosity IndexesV.
Annals of the Association of American Geographers 5 8 ( 2 ) : 3 7 1 . : . B
T a i nguyen va M o i trtfilfng o c K y i -Thong 2/2020 ^ * '
