' KHOA HOC CONG NGHE •
NGHIEN CIJU GIAI P H A P K Y T H U A T T R O ' NLPQC N H A M
HAN CHfe UNG NGAP DO MITA TAI CAC DO TH! TAP TRUNG
VUNG DdNG BANG S 6 N G C I J U LONG
Ts. T 6 Q U A N G T O A N Vien Khoa hgc Thuy Iffi mien Nam PGS.TS. NGO VAN QU^N, THS. GIANG THJ THU THAO
Trir&ng Dai hpc Thuy Iffi
Tom tat: Ung nggp do mua tai cdc do thi tap trung ngc^ cang dien bien phuc tap va tra nen nghiem trong han ca ve muc do nggp sdu, thai gian nggp keo dai, miic do thu&ng xuyen xqy ra, ung nggp xdy ra ngay ca khi mua vica tap trung thai gian ngdn a cdc do thi vung dong bang song Cicu Lon, dgc biet a cdc do thi nhu Cdn Tha, Vinh Long, Ca Mau... Vai su gia tang luang mua Ian he thong cong rdnh do thi hdu hit duac thiSt ke tic Idu nen khong dii ndng luc tieu thodt nuac mua hi?n nay lam dnh huang den dot song sink hogt cua ngudi dan vdphdt trien kinh te-xd hoi trong vung. Vi vgy, muc tieu chinh cua nghien cuu nay tap trung vac van de gidiphdp ky thugt nhdm gidm thieu ung nggp do mua tgi cdc do thi tap trung vung dong bang song Cuu Long. Kit qud nghien cuu cho thdy, luang mua trung binh tang len 3-6% trong dieu Men BDKHden nam 2010, luang mua ngdy Ion nhdt a cdc tinh DBSCL da gia tang tuang duang vai muc thay doi 9-17,5% trong han 20 nam qua, dgc biet vai cdc tran mua di thuang luang mua tang len vai mice thay doi tuang duang 20% den nam 2100. Ket qua tinh toan thuc te cho thdy, khi tinh toan vai luang mua trung binh gia tang trong dieu kien BDKHden 2100 la 3-6% thi chi cdn bo tri mot dung tich tru 0,3 din 0,6 m^ cho moi 100 m2 xdy dung thi CO the gidi quyet tot van de mua luang mua gia trang vai muc 3-6% trong tuang lai. Ket qud nghien cuu cung cho thdy, de gidi quyet tinh hinh ung nggp do mua di thuang Men tgi vung DBSCL vai cdc tran mua cue doan tang len 20% den nam 2100 va de gidm 20% tong lu(mg mua rat, chi cdn bo tri mot dung tich trie 2,2 den 2,5 m^ cho 100 m2 xdy dung. Ket qud nghien cuu cung chi ra hieu qud cua gidi phdp tich nude mua tgi cho c6 the thdy ro han khi phan tich cu the cho truong hap Tp Cdn Tha vai gidi phdp tich nuac 20% luang mua gia tang neu a dieu kien him tgi, binh quan hang nam c6 140 ngdy co mua, thi nhung ngdy c6 mua duai 25mm duac xem la duac gidi quyet triet de nha he thong tru nuac tgi cdc cong trinh, ket qud la chi con han 20 ngdy duac xem Id co mua. Tuang tu, vai mice mua han 40mm thi co the gidm duac V2 so trgn mua co the gdy nggp vd luang mua con Igi tieu thodt vdo he thong icng vai mua tieu thiet ki 10% thai dogn 90'(P=86mm) chi cdn tuang duang vai trgn mua co tan sudt khodng 60% (P=61mm). Nhu vgy khd ndng ddm bdo tieu thodt se duac cdi thien tot, tic do cho thdy gidiphdp hieu qud chong ung nggp do mua tgi cdc do thi tap trung hien hieu d vung DBSCL. Ket qud nghien cicu cung cap cho cdc nha quy hogch, quan ly tdi nguyen nuac dua ra chinh sdch vd chien luac khai thdc vd qudn ly nguon nuac mua nhdmphdt trien kinh te- xd hoi mot cdch ben vung cdc khu do thi tap trung viing dong bang song Cicu Long.
Tix khoa: Do thi, ling ngap, bien doi khi hau, dong bang song Cuu Long.
Abstract: The inundation by rainfall in urban areas are becoming increasingly complex and are becoming more serious in terms of inundation level, long time of inundation, frequent inundation and even inundations, inundation occured even when the rainfall in a short time in urban areas in the Mekong River Delta, especially in urban areas such as Can Tho, Vinh Long and Ca Mau. With the increase in rainfall, the majority of urban drainage systems are designed so long ago that they
T A P C H I T A I NGUYEN Nl/(5C $64-2018 3
• KHOA HQC CONG NGHj: •
are not capable of draining rain water nowadays, leading about affecting people's living conditions and socio-economic development in the area Therefore, the main objective of this study is to focus on the technical solution to reduce inundation in urban in the Viet Nam Mekong Delta The results show that the average rainfall increases 3-6% in the climate change condition to year of 2100^ the largest daily rainfall in the VN Mekong Delta has increased equivalent to the change 9-17.5% in over the past 20 years, especially with anomalous rainfall increased with a change of 20%
equivalent to year of 2100. Actual calculation results show that when calculating with the increase of average rainfall in the climate change condition to 2100 is 3-6%, only need to allocate a storage capacity of 0.3 to 0.6 m' per 100 m' of construction can be resolved well rainfall is expected to increase at 3-6% in the future. The results also show that in order to solve the inundation problem due to rainfall in the VN Mekong Delta with extreme rainfall increases to 20% by 2100 and to reduce the rainfall by 20% that is need a storage capacity of 2.2 to 2.5 m for 100 m of construction area. The results also show that the effectiveness of the on-site rainwater solution can be seen more clearly when analyzing the case of Can Tho city with 20% rainfall increase in case of current conditions, the annual average of 140 days with rain, the days of rain below 25mm is considered to be thoroughly resolved base on the water storage system at urban areas, resulting in only more than 20 days are considered rain. Similarly, with rainfall over 40mm, it is possible to reduce '/i of the rainfall that can cause inundation and the remaining rainfall drained to the system with a design rainfall 10% of period for 90 min (P = 86mm) that is only equal to the rain frequency is about 60% (P = 61mm). So, the drainage capacity of the urban area will not be inundated which shows the effective solution against inundating in urban areas in the VN Mekong Delta. Moreover, the research results provide planners and water resource managers with policies and strategies for the exploitation and management of rainwater resources for sustainable socio-economic development of urban area in VN Mekong Delta.
Key words: Urban, inundation, climate change, Viet Nam Mekong Delta.
1. TONG QUAN triSn kinh te-xa hoi trong vung, nhu viec di lai D6ng bang song Cuu Long la viing ha luu kho Ichan, bat tien, anh huong din ve sinh m6i cu6i Cling ciia luu vuc song Mekong, dien tich truong (nuac cong ranh t r ^ len mat du6ng...), toan vung chiem 3.9 trieu ha bao gom 13 tinh. anh huong den viec kinh doanh buon ban cua La vung trung thap, dien tich dSt canh tac co cao nhiSu ho kinh doanh, va da tro thanh luc can dp tir 0,5m den 1,5m chiem 92,7% va co y nghia trong qua trinh phat tri^n cua cac do thi, tao tam v6 cung quan trong ve kinh te - xa hoi cua Viet li biic xuc cua nguoi dan khi ma chieu sau ngap.
Nam (Hinh 1). Tuy nhien, vung DBSCL dang s6 ISn ngap ngay cang gia tang [10]. Ung ngap cr chiu nhung thach thuc rat Ion do nhung tac cac do thi vung DBSCL g6m nhilu nguyen dong ctia thien tai, bien doi khi hau va dac biet nhan nhu: do lu phia thuong ngu6n, do trieu la via ik ling ngap do mua tai cac do thi [10]. cu6ng, he thdng tieu thoat con han ch8, viec Trong nhttng nam gin day, vin ih ling ngap tai phit trijn do thi, hay do thi hoa tang cao trong cac khu do thi tap trung a DBSCL ngay cang tro khi co so ha ting tiSu thoat khong dap ling kip, nen nghiem trong hon ca ve miic do ngap sau, he th6ng tieu thoat nuoc mua hien hixu chua thai gian ngap keo dai, miic do thuang xuyen dam bao, qui hoach quan \j ling ngap con chua xay ra, ling ngap xay ra ngay ca khi mua vira tap dam bao (ty le dien tich khu trit dem va diSn trung thai gian ngSn... dac biet 6 cac do thi nhu tich do thi hoa nho), thilu cic giai phap phu trcr Cin Tha, Vinh Long, Ca Mau... lam anh huong nhlm cat giam lira luang cSn tieu, va dac biet la dSn doi s6ng sinh hoat cua nguoi dan va phat mua 16n v6i nhiJng tran mua cue doan ngay 4 TAPCHlTAlNGUYeNNUOCS64-2018
• KHOA HpC CONG NGHE •
cang xuat hien nhieu han... M^c du da c6 nhi8u giai phap duoc thirc hien nhu vi?c ton nen, len d6 bao, c6ng ngan tri6u va lu, tang cuang kha nang tieu thoat cua he thSng duang ong bang nSng cap he thdng... Tuy nhiSn, viec thirc hien chua dong b6 va keo dai, khong theo kip dugc toe dp gia tang do thi hoa nen tinh trang ngap vIn thucmg xay ra 6 cac khu d6 thi [6] [4].
Hinh 1.1: Viing DBSCL (Nguon: UNDP) Vi vay, de han che van de ung ngap thuang xuyen xay ra tai cac khu do thi tap trung trong nghien cmi ngay tac gia se tap trung nghien cuu phap ky thuat tru nuoc mua nh5m giam thi6u ling ngap do mua tai cac khu do thi vung dong bang s6ng Cuu Long la giai phap chu dOng rdt cSn thiet trong chien luge nghien cuu chong ling ngap a khu vuc DBSCL.
2. CO S d DE XUAT GIAI PHAP VA PHlTONG PHAP NGHIEN CUtJ
2.1. V^n di (td th{ hoa, mua loti v^ die thn tai Hien nay, toan viing Dong bang song Cuu Long CO 161 do thi. Duoi tac d6ng cua thien tai, 15 thanh pho ciia vung dong bang s6ng Cuu Long deu bj ung ngap do ca lu, trieu cuang va do mua Ion, dac biet la cac tran mua Ion tai cac do thi phat trien tap trung, khong gian chiia nuac va c ^ kenh chuy6n nuac ket noi vai he
thong tieu thoat nuac con rat hgn che. Nhung nam gan day do tac dong cua bien doi khi hau lam cho che do mua lu thay d6i cue doan, muc nuac bien dang khien tinh trang ngap lut a Dong bang song Cuu Long, dac biet cdc do thj dien ra ngay cang gay gat. Muc nu6c lu t^ Tan ChSu nam 2011 thap han nam 2000 la 20cm, nhung muc nuoc lu tai Can Tha nam 2011 lai cao hon nam 2000 la 20cm. Dac bi§t, tinh trang ngap do trieu, ngap do lii 6 tat ca cac do thi Can Tho, Vmh Long, Tien Giang, Long An, Dong Thap, Ca Mau, An Giang... ngay cang tang vai toe do nhanh nhu dugc thS hi$n trong Bang 2.1 [12].
Bang 2.1: Danh gia muc d9 ngap nghiem trong cac do thi vung DBSCL
TT
1 2
3 4 5 6
TMiih pbo, thi x3
CinTho Tan An LongXuySn
CaMau Bac Lieu My Tho
Mlic do
1 (cao) 1 1 1 1 1
TT
7 8 9 10 11 12
T h ^ p h ^ , Ihixa VTnh Long S&Tring Ki&n Giang H^u Giang DfingThSp TrJVinh
Mlic do
1 2(lningbinh)
2 2 2 2
Ben canh do, nhung tran mua Ian a cac do thi la nhiing van de Ion va da tra thanh lytc can trong qua trinh phat trien cua cac do thj. C\i the, nhung tran mua tr6n lOOmm da thay d6i tir thap nien 50 vai 0 tran, len 1 tran a thap nien 60, va tang dot bien a thap nien 2000 voi 9 tran/8 nSm, nh&ig tran mua co tong luang 135mm dS xuat hien ngay cang nhi^u, va dSc diSm mua gay ng$p a DBSCL CO thai doan ngan (c6 thai do?n ngan (tir 60phut d&n 90 phut) d6ng thdi cac khu do thi cii CO mat dp dan cu cao da anh huong Ion dSn kha nang tieu thoat dan den van de img ngap ngay cang tang [10]. Mot trong nhung van d% t6n tai nfia la tiong he thong tieu thoat nuac do thi da dugc thiet ke tir truac, chua dap ung dugc miic dp gia tang dan so nhanh va mat dp xay dung qua
TAP C H I T A I NGUVeN N J(5C S6 4-2018
• KHOA HQC CONG NGHE • muc lam cho kha nang thkm va di^u ti^t giam,
nuoc tap trung nhanh ve he thong lam cho he thong khong tieu thoat kip, gay ngap.
2.2. Cor so* de xuat giai phap
Nhu da dugc phan ti'ch a tren, do dac diem ve mua gay ngap a DBSCL co thoi doan ngSn.
Theo kich ban cua Bp TN&MT ban hanh thi lugng mua ngay a khu vuc cac tinh DBSCL co su bi^n d6i rkt khac nhau. Trong dieu ki?n BDKH lugng mua a DBSCL theo kich ban BDKH qu6c gia dugc du bao tang 3-7%, cuang dp mua ngay thay doi cham, tuy nhien so lugng cac tram mua Ion, dac biet la mua trSn 100mm dugc xem la co xu the tang kha ro ret, ngoai trii a B^n Tre, Chau D6c va Rach Gia co xu the giam con lai deu co xu the tang (Bang 2.2) tir do din d6n cuang d6 mua tieu ngay mot tang.
Bang 2.2: Ket qua phan tich xu the thay doi Itrgng mua ngay \&n nhat trong nam theo binh quan 10 nam va tan so mua lom hon
100 mm theo binh quan 10 nam
dap ung dugc trong dieu kien BDKH, lam cho ng^p a cac khu do thi cang tro len nghiem trpng han. Ngoai ra, dk xem xet anh huong do mua dSn ngap li6n quan d§n kha nang ti6u thoat cua he thSng, nghien ciiu phan tich so ngay c6 mua trong nam va ngay co miic nude song vugt cic cao trinh khac nhau. K8t qua phan tich cho giai doan 1978 dan 2011 (Hmh2.1).
Tinh
Long An Dong Thap
Ben Tre Tra Vinh An Giang C ^ T h a SocTrSng
Bac Lieu Ki6n Giang
a Mau Tram
mua
MocHoa CaoLanh B^nTre Cang Long Chau Doc Can Tha Soc Trang Bac Lieu Rach Gia CaMau
XutheciroTig dp mua ngay Ion nhal theo binh quan 10
nSm Giam Ting Giam Tang Giam Tang Tang Tang Giam Giam
XuthetansS ngay mua qua 100 mm trong nam theo binh quan lOnSm
Tang Tang Giam Tang Giam Tang Tang Tang Giam Tang
Nhu vay, cuong 46 cac tran mira Ion gia tang la kha ro ret, dflng nghia voi no, cac he thdng tieu thoat nuoc mua hien hiru dugc thiSt ki chua tinh den luong mua gia tang nay. Do do trong tuong lai, co tinh dSn bidn d6i khi hju thi kha nang tieu thoat cua he th5ng tieu se giam, khong
Hinh 2.1: Duong luy tich thai gian binh quan s6 ngdy trong muc nuac vuat cdc ngudng khac nhau,
ngay co mua vd ngdy co mua Ian hem 30mm K6t qua cho thdy, binh quan giai doan 1978 den 2011, so ng^y c6 mirc nuoc ngoai song vugt qua cao trinh 1,5m chilm khoang 40 ngjy, trong do khoang 20 ngay co mua va trong s6 ngay nay s& ngay co mua vuot qua 30mm chilm 2-3 ngay. Vi vay, r4t cin thidt co giai phap giam miic do ngap do mua gia tang va co xet d6n gia tang m$t do xay dung cr cac do thi de dam bao viec tieu thoat nuoc mua dat hieu qui.
3.3. Tinh toan giai phap ky thuSt cka tra luyng niro^c mira gia tang de chong ung ngap tai khu do thj tap trung
a. Tinh toan giai phdp tieu thodt nu&c mua theo luang mi^a gia tang duac lay tit kich ban BDKHciiaBgTNMT.
Gia thiSt h$ th6ng tiSu hifin hflu da dip ilng duoc yeu cau tieu thoat nude ciia do thi trong qua khii, cIn phai giai quyet van de mua gia tang Uong dilu kien BDKH; Mua ti4u ftak kS 10% voi thoi doan 90 phiit co t6ng luong mua 86mm cung voi luong mua tang do BDKH dto 2100.
5 TAPCHfTAlNGUY£NNLr(3CS64-201l
• KHOA HQC CONG NGHf ^ Tren ca sa lay lugng mua tieu thi6t kk tran tin
suat 10% la 86mm, tinh dugc lugng mua gia tang theo kich ban BDKH, t6ng lugng nuoc mua gia tang tren 1 ha la lugng nuac can trii cho 1 ha de dam bao he thong tiSu thoat hien hiiu vSn lam vi6c bmh thu5ng trong tuong lai. Dung tich cln tra cho m6i 100 m^ xay dimg dugc tinh toan co xet dSn lugng tru bo sung cho phSn dat khong xay dung nhimg bi be toi^ hoa (nhu duang gjao thong, via he...). Ket qua tinh toan chi tiet cho tung thanh pho a DBSCL dugc the hien a Bang 3.1.
Bang 3.1: Lirgng mira can trir theo 100 m^
dat xay dvng khi xet den mira tang trong dieu ki^n BDKH
III
(1) Long An DongThSp Ti^n Giang Ben Tre Vinh Long Trii Vinh An Gians CSnTho HSu Giang S6cTr5ng Bac Lieu Kien Giang
a Mau
%
tang dell 2100 (2) 5,6 4.3 2.9 3,3 4,3 4,4 3 4,3 4,8 5,5 4,6 4,4 3,9
Luong mua tian tang (mm) (3) 4,82 3,70 2.49 2.84 3,70 3,78 2,58 3,70 4,13 4,73 3.96 3.78 3,35
Wlnl Choi ha (m'l
(4) 48,16 36.98 24,94 28,38 36,98 37,84 25.8 36,98 41,28 47,3 39,56 37,84 33,54
Wire cho 90%D TXD
(m') (5) 53,5 41.1 27,7 31,5 41,1 42,0 28,7 41,1 45,9 52,6 44,0 42,0 37,3
Wlrit cho 100 m=
(m=) (6) 0,54 0,41 0,28 0,32 0,41 0,42 0,29 0,41 0,46 0,53 0,44 0,42 0,37
K§t qua tinh toan cho thay chi can b6 tri mOt dung tich triJ 0,3 din 0,6 m'^ cho m6i 100 m^
xay dung thi c6 the giai quyet tot van de mua gia tang lugng mua voi muc 3-6% trong tuang lai. Day dugc xem la kha thi vi voi dung tich nay la hoan toan co the bo tri, dap ung dugc ma khSng anh huong den ket cau ciing nhu di?n tich cac c6ng trinh xay dung.
b. Tinh toan gidi phdp tieu thodt nude mua theo luang mua bat thucmg thuc te a khu v{cc DBSCL
Hien nay rit it cac nghiSn cuu dy bao s\r thay d6i lugng mua ngay theo cac kich ban bi6n d6i khi h^u, djc bi?t cac tran mua Ion.
Trong nghien curu nay, tren ca so tham khao kit qua nghien cicu danh gia thay doi lugng mua ngay ung vai cac tan suat khu virc mien Trung giai doan truac nam 1990 (1970-1990) so vai giai doan tu 1991 den nay (1991-2011) nhu dua ra a Bang 3.2.
Bang 3.2: Thay 6hi lu-tmg mira ngay trong di^u klf n BBKH
T^ng lui?ng mira 24h Ihay doi (mm) TSnsuiit(N5m).
KB Thap Tning binh Cao
2 136,8 141,2
178,3 5 199,5 230,7
292,9 Ty 11 thay doi cDa luon Kich
ban Thap Tning binh Cao
2
-14,3 -11,6
11,6 5
-14,7 -1,4
25,2 10 240,1 292,8
372,3 20 279,9 352,3
448,7 50 331,5 431,9
550,7 100 369,6 490,2
625,5
^ mua 24h (qua khu-tuong lai) (%) 10
•15,2 3,4
31,5 20
-15,2 6,7
35,9 50
-15,3 10,4
40,8 100
-15,4 12,2
43,1
Ket qua cho thay, thay d6i lugng mua ng^y trong tuong lai co bien doi rdt khac nhau theo cac kich ban, voi kich ban thip luong mua ngay CO xu the giam. Trong kich ban trung binh vk cao, viH cac tran mua vtji tin suit thip thi xu the lu<;mg mua gia tang nhiSu hon, nguoc lai cac t r ^ mua vai tan suat cao 2-5% thi thay d6i t6ng lugng mua la it hom. D6i vtW mua tieu 10% thay doi luong mua gia tang til 3,4 din 31,5%.
Nghien ciiu nay phan tich thay doi cuong do mua ngay Ion nhit trong nam mot s6 tram 6 DBSCL tir chuoi so lieu lich su d% co dugc danh gia cac biSn dong mua nhiing nam gin day phuc vu du bao trong tuong lai. Nghien ciiu phan tich
TAPCHfTAl N G U Y C N NLTtJC 5(34-2018
• KHOA HQC CONG NGHE •
thay doi mua ngay Ion nhat trong nam tu giai doEin 1990 tra vh truac so voi giai d o ^ tu 1991 den nay. Ket qua dugc dua ra a Bang 3.3.
Bang 3.3: Phan tich cirfrag d6 mira ngay Ion nh^t theo cac tram viing DBSCL
giai doan trirorc va sau 1990
p
(%)
1 5 10 50
CinTho Tmoc
1990 135,7 116,1 106,7 78,6
Sau 1990 152,8 134,7 125,4 94,5
Bac Lieu Tiuiic
1990 188,7 157,3 141,5 91,2
Sau 1990 232,0 177,1 153,1 93,6
CiMau T n i *
1990 195,6 156,8 139,7 96,5
Sau 1990 185,9 164,5 153,5 117,3
Ket qua phan tich cho thay, ung vai mua tieu tin suat 10%, lugng mua ngay Ion nhat co xu the gia tang tit 10-20mm o giai doan sau 1990 so voi truoc 1990, tuong duang vai muc thay d6i 9-17,5% tai cac tram.
Ket qua thuc te cho thay mua Ion a khu vuc mien Trung la 16n hon nhieu so voi cr DBSCL, lugng mua ngay Ion nhSt a khu vuc miSn Trung CO the len tdi hon 500mm (Da Nlng), 800mm (Van Canh) trong khi a DBSCL moi ghi nhein dugc la 260mm (tai Rach Gia). Can cii vao kk qua phan tich thay doi cudng do mua ngay Ion nhat mot so tinh DBSCL nhung nam gha day, xet den nhung yeu td biSn d6i trong tuong lai, va tham khao cac du bao ve bien d6i lugng mua o khu vuc mign Trung trong dilu kien BDKH nghien cuu gia thiet rang cuong dp mua Ion a DBSCL CO thS tang 20% so vai hien tai, dugc xem la bang trung binh cao so voi khu vuc mihn Trung (31,5%).
Thuc te cho thay hien tai cac h6 thSng tieu thoat nuoc mua a cac do thi hien hiiu da dugc xay dung tir lau, chua xet d%n su gia tang do thi hoa nhung nam gan day, chinh vi vay khong dap ung dugc yeu cau ti8u thoat nuac hien hiru.
Viec dau tu nang cap cac he th6ng nay se t6n ca thoi gian va von dau tu, trong khi vin dh ngap dien ra tiurong xuyen sau m6i tran mua Ion. Vi vay, yeu ciu dat ra la cin cai tiiien t6t hon tinh
hinh tieu nuac hien tai bang vi$c gia tang tich trir tai cho 20% lugng mua (xip xi voi lugng mua ma co thS gia tang hon trong dieu ki^n BDKH) va lugng mua gia tang bmh quan trong diau ki6n BDKH.
Lly lugng mua tieu fliiet kk 10%, thai dogn 90' CO t6ng lugng mua la 86mm, kk hop voi mua tang trong diSu kien BDKH din 2100. Lugng tich nuoc t^ ch6 20% dugc xem la xap xi voi lugng mua ngay co thS gia tang trong dieu kien BDKH a kich ban tir trung binh den cao. Ket qua tinh t o ^ dung tich cin trii cho moi lOOm^ dien ti'ch xay dung dugc dua ra 6 Bang 3.4.
Kit qua ti'nh toan cho thay, neu chi cdn b6 tri mot dung tich tru 2,2 den 2,5 m'* cho moi 100 m^ xay dung thi co the giai quyet t6t van dh mua gia tang vol muc 3-6% tiong tuang lai va mua CO the bien doi di thuang. Day dugc xem la giai phap kha thi vi vai diuig tich nay la hoan toan CO the bo tri, dap ung dugc ma khong anh huong din ket cau cung nhu dien tich cac cong trinh xay dung.
Bang 3.4: Lirpug mira can trir theo 100 m^
dat xay dijraig co xet den dd thi hoa gia tang
III
Long An Dong Thap Tien Giang Ben Tre vinh Ixing
Tra Vinh An Giang Can Tho Hau Giang S6cTr»ng BacLidu Kien Giang CiMau
mua tSug den 2100 5,6 4,3 2,9 3,3 4,3 4,4 3 4,3 4,8 5,5 4,6 4,4 3,9
Luong mua c4ntrir
(mm) 22,02 20,90 19,69 20,04 20,90 20,98 19,78 20,90 21,33 21,93 21,16 20,98 20,55
Wtrit Choi ha (ra') 220,16 208,98 196,94 200,38 208,98 209,84 197,8 208,98 213,28 219,3 211,56 209,84 205,54
Wtril cho 90%D TXD (m') 244,6 232,2 218,8 222,6 232,2 233,2 219,8 232,2 237,0 243,7 235,1 233,2 228,4
Wtril cho 100 m' (m') 2,45 2,32 2,19 2,23 2,32 2,33 2,20 2,32 2,37 2,44 2,35 2,33 2,28
8 TAP CHlTAlNGUVeNNirOC 5(54-2018
• KHOA HOC CONG NGHE •
Tir ket qua tinh toan cho thiy, voi yeu cau dat ra miic trii nhu tren, kit hgp yeu cau v$n hanh xa nuac tu hk chiia ra h$ thdng sau 8-12h thi nhung tian mua ngay ca voi cuong dO cao nhung duai 20-25min dugc xem la kho co kha nang gay ling ngap dudng tgi cac khu do thi tap trung tai vimg DBSCL.
L L
Hinh 3.1: Phan tich hi$u qua cua gidi phdp tich nude mua tgi cho Hieu qua cua giai phap tich nuoc mua tai cho c6 thi thiy ro hon khi phan tich cu thS cho trudng hgp Tp Can Tho nhu d Hinh 3.1, voi giai phap tich nuac 20% lugng mua hien huru va lugng mua gia tang tiong dieu kien BDKH, ket qua phan tich cho thiy, niu a dieu ki^n hien tai, binh quan hang nam co 140 ngay co mua, thi nhung ngay co mua duoi 25mm dugc xem la dugc giai quyet triet de nho he thong trii nuac tai cac cong trinh, ket qua la chi con han 20 ngay dugc xem la co mua.
•fe
Hinh 3.2: Mua theo thai dogn ngdn img vdi cdc tan sudt khac nhau a DBSCL Tuang tu, voi miic mua han 40mm thi co thS giam dugc 'A so tian mua co the gay ngap va lugng mua con lai tieu thoat vao he thong ling vai mua tieu thiet ke 10% thai doan 90'(P =
86mm) chi con tuong duang vai tian mua co tin suat khoang 60% (P = 61mm) (xem huih 3.2). Nhu vay kha nSng dam bao tieu thoat sS dugc cai thi?n tot, tii do cho thay giai phap hi§u qua ch6ng ling ngap do mua tai cac do thi tap trung hien hiiu a vung DBSCL.
4. KfiT LU^N
Tir cac kit qua nghien ciiu cho thay, d% giai quyit vin di ling nggp do mua tai cac do thj tgp trung hien huu la mgt nhu cau cap bach a cac thanh ph6 khu vuc DBSCL. Trong hon 20 nam qua lugng mua ngay Ion nhat a cac tinh DBSCL da gia tang 6 miic rat ddng quan tam, dgc diem mua tai vung DBSCL co tinh tuang ty nhu 6 khu vuc TPHCM, thuc ti ket qua nghien ciiu cho thiy, tai TPHCM lugng mua tian trSn 100mm o thap nien 50 la 0 tran, thgp nien 60 la 1 tian, len 2 tran a thgp nien 70 va 80, roi tSng len dang ke a thap nien 90 voi 4 tian, va tang dgt biin 6 thap nien 2000 voi 9 tian/8 nam. Ket qua nghien ciiu cho thay, lugng mua tian b DBSCL sau nam 1991 v6i tin suit 5 va 10% a tit ca cac tigm diu gia tang tic 10-20mm so vai truac 1990, tuong duang voi mure thay doi 9- 17,5%. Voi su gia tang lugng mua Ion nhat nhu vay, he thong cong ranh hau het dugc thiet ke tir lau nen khong du nang l\rc tieu thoat nuoc mua hien nay. Vi vay nghien ciiu giai phap chong ung ngap do mua cho cac do thi bang giai phap be chiia nuoc mua nhim lam giam dong chay do mua la rat can thiet va thiet thuc. Ben canh d6, hau het cac thanh pho a khu vuc DBSCL deu 6 tinh trang khai thac nuoc ngam qua miic gay lun sut Tp. 6 muc nghiem tiong, vi vgy cac be chiia nuac mua khong chi nhim ch6ng iing ngap ma con ket hgp cung cap nuoc sinh boat cho cac d6 thi se dem \ax s\r phat triin bin vung o cac do thi.
Kit qua tinh toan th\ic ti cho thiy, khi tinh toan vai iugng mua cin trft theo 100 m^ dit xay dung khi xet din mua tang tiong diiu kien BDKH, Mua tieu tiiiit ki 10% voi thai dogn 90 phiit CO t6ng lugng mua 86mm ciing voi lugng mua tang do BDKH din 2100 thi chi cin b6 tri mpt dung tich tru 0,3 din 0,6 m^ cho moi 100
TAP CHllAl NGUYEN Nl/OC S(5 4-2018
• KHOA HQC CONG NGHg •
m xay dung thi co the giai quyet tot van de mua gia tang lugng mua vai miic 3-6% tiong tuong lai. Kit qua nghien ciiu ciing cho thay, de giai quyet tinh hinh ung ngap do mua hien tai vung DBSCL, chiing ta cin trii tai cho tir 9 - 17,5% t6ng lugng mua, hay vai cac tran mua cue doan tinh tang len 20% den nam 2100 va de giam 20% t6ng lugng mua roi, chi can bo tri mpt dung tich \ni 2,2 din 2,5 m^ cho 100 m^
xay dung.
Kit qua nghien ciiu cung chi ra hieu qua ciia giai phap tich nuoc mua tai cho co the thay r6 hon khi phan tich cu the cho truong hgp Tp can Tho v6i giai phap tich nuac 20% lugng mua gia tang neu 6 dieu kien hien tai, binh quan hang nam co 140 ngay co mua, thi nhiing ngay co mua duoi 25mm dugc xem la dugc giai quyet triet d& nha he thong trii nuoc tai cac cong trinh, kit qua la chi c6n hon 20 ngay dugc xem la co mua. Tuang ty, vai miic mua hon 40mm thi co the giam dugc 14 s6 tran mua CO th6 gSy ngap va lugng mua con lai tieu thoat vao he thdng ung voi mua tieu thiet ke 10%
thai doan 90'(P^86mm) chi con tuong duang voi tian mua co tin suit khoang 60%
(P=61mm). Nhu v^y kha nang dam bao ti6u thoat se dugc cai thi|n tot, tu d6 cho thiy giai phap hieu qua ch6ng ung ngap do mua tai c^c do thi tap trung hien hiiu 6 vung DBSCL. Kit qua nghien cihi ciing cung cap cho cac nha quy hogch, quan ly tai nguyen nuac dua ra chinh sach va chien luge khai thac va quan ly ngu6n nuac mua nhim phat triin kinh ti-xa hoi mOt each bin vung cac khu do thi tap trung vung dong bang song Ciiu Long.
TAI LIEU THAM KHAO [1] Sam L, Lan NV, Vugng ND (2006), Co so khoa hpc xay dyng ho sinh thai vimg ngap lu D6ng bang s6ng Cim Long. Tuyin tap kit qua KH&CN Vien Khoa hpc Thuy Igi Miin Nam.
Nha xuit ban Nong nghiep.
[2] Sam L, Lan NV, Vugng ND (2006),
Nghien ciiu xay dung he thfing h6 sinh thai - co so phat triin bin vung vung Dong bing song Cim Long va miin Trung. Tuyen t|ip ket qua KH&CN Vi?n Khoa hgc Thuy Igi Miin Nam.
Nha xuit ban Nong nghiep.
[3] To Quang Toan, Ngo Van Qu$n, (2016).
Nghien ciiu giai phap ky thuat tru- nuoc ngpt cho phuc vu nuoi ti6ng thuy san vimg ven biin d6ng bang song Cim Long.
[4] PCS. TS Tang Dire Thing (2011), Nghien ciiu cac giai phap chong ng$p Tp. H6 Chi Minh.
[5] Ngan hang Thi giai WB (2012), Huong din vi quan ly rui ro ngap lut do thi tong hpp cho the ky 21.
[6] Nguyen Thi Phuong Thao (2013), Nguyen nhSn ngap ling Tp.Nha Trang.
[7] Nguyen Dang Tinh (2011), Mot s6 giai phap chong ung ngap 6 TPHCM.
[8] Phan Manh Himg (2015), Giai phap cong trinh giam thieu ngjlp lut khu vyc npi thanh TP.Nha Trang.
[9] Nien giam thSng ke (2012), Nien giam thong ke cac tinh Dong bang song Cim Long.
[10] UNDP (2016), Nghien cuu quan ly ting hgp tai nguyen nuac trong diiu kien biin doi khi hau, nuac biin dang va sy phat triin nhanh nen kinh te, xa h6i a ding bing Song Ciiu Long, Viet Nam.
[11] Sarah Opitz-Stapleton (2013), Kich ban ve mua cue tri 6 Tp Da Nlng, mang luoi cac thanh ph6 chau A co kha nang chong chiu voi BDKH, ISET.
[12] Luu Diic Cuang (2016), Phat tiiin do thi thich ung voi bien d6i khi hau a vung DBSCL.
[13] Bp TN&MT (2016), Kich ban BDKH va nuoc biin dang cho Viet Nam.
Ngudi phan bien: PGS.TS Nguyen Cao Dffn Phanbi^nxong: 7/2018
10 TAP CHf T A I NGUYEN Nl/OC S6 4-2018
