I KHOA HQC" CONG NGHE
GIAI PHAP C 6 N G T R I N H GIAM THIEU NGAP L^T KHU Vy^C NQI THANH TP. NHA TRANG
ThS. Phan Manh Hiing, TS. Nguyen Hfru Nhan, ThS. Do Thi Hong Thir Viin Ky thugt Biin
T6m tdt: Thdnh phd Nha Trang Id mot diem din du lich hdng ddu ciia cd nudc. Tuy nhiin trong thdi gian qua, tinh trgng ngdp It^t khd thudng xuyen xdy ra ldm dnh hudng khdng nhd khdng chi den cuge sdng ngudi ddn md con tde ddng mgnh din ngdnh cdng nghiip khdng khdi ndy. Dac biet la sau trgn mua lU cudi ndm 2010 vdi thiet hgi ngng ni thi nhimg gidi phdp ddng ddn cho vi^c gidm thiiu ng4p Ivt cdng hit sue nhdt thiet vd cdn triin khai nhanh chong. Bdi bdo se trinh bdy mgt sd gidi phdp hihi hi$u chdng ngdp lut cho Tp Nha Trang vdi ddc trung Id mot dd thj ven biin cd Iuang mua gdn 1800 mm/ndm, cd sdng ldn di qua cUng nhu bi tde ddng mgt phdn nhd bdi trieu. Cdc gidi phdp duac dua ra se giup cho cdc ca quan ban ngdnh cd liin quan trong cdng tde qudn ly, quy hogch dd thi phdng chdng ngdp lut
Tir khoa: lU, nggp lyt, chda nudc, gidi phdp, cdng h-inh, gidm thiiu, Nhg Trang.
Summary: Nha Trang is the one of interesting cities on tourist in Viet Nam. Nevertheless, the flood's occurrence in Nha Trang city recently affects not only human life but also tourist field.
Especially, after huge damage in the end of 2010's flood, solutions to reduce flood are really compulsory. This paper will present some effective measures on flood control for Nha Trang with characteristic of high rainfall nearly 1200 mm/yr, river flood and tide. These solutions will help related agencies in urban manage and planning to flood control.
Keywords: Flood, inundation, storage, measures, structure, minimization, Nha Trang Lfii^TVANDE
Thanh phd Nha Trang ndm Ipt gifla nhiing ddy nui va Id vimg hg Iuu cua song Cdi cd luu vuc rpng ldn. Bfin canh nhiing uu diem ve khi hdu, canh quan,... thi ciing cd n ^ y ca tifim dn khi nudc mua, lfl tii thupng ngudn do vfi, myc nudc sfing dang cao de gay ngdp ung trong thdnh pho.
Khu vyc nfii thanh thdnh phfi chia lam 3 phdn:
Khu vyc phia Bdc cd dja hinh doi niii, ddn cu trai ddi tir chdn niii ra den mep bien vd men theo song Cdi co cao dp thay doi tir 373 m dfin 0,5m. Cdc khu dan cu ndm men theo cac chdn mii Hon Kho, Hdn Sgn, Hdn Ch6ng, c6 dia hinh doc nfin nudc thuorng tgp trung d khu vyc NgiTJn phan bi^n: PGS.TS Hoftng V3n Hudn Ng4y nh§n bai: 02/7/2013 - Ngdy thong qua phin bi§n:
30/8/2013-Ngiy duy?t dang: 10/9/2013
trung, thap gay nggp thdi gian dai sau mua.
- Khu vyc trung tdm la vimg dfing bdng duyfin hai, cao d$ thay doi khong nhieu, tnmg binh khoang 5,5m, ndm men theo dudng vdng cung dm ldy Vinh Nha Trang.
Khu vuc phia Nam cd cao dp gidm ddn tfl Bdc xuong Nam roi tang mgnh den khu vyc mii Chut. Cao dp thay dfii tu 2 den 130m.
Nguyfin nhdn gdy nggp Tp. Nha Trang cd thi ndi la rat phfle tap, do mua, bao, lfl, trieu va cd con ngudi. Chinh vi vaiy tun kiem nhihig gidi phdp gidi quyet tript de nggp lut cho thdnh pho Id mpt thach thuc ldn, dupc UBND tinh Khdnh Hda rdt quan tam. Trong nhiing ndm qua, cdc cap, cdc nganh cfla dja phuang da phfii hpp, chfl dpng ddi phd vdi cdc tinh hudng, giam thifiu toi da thipt hgi do mua, lu xdy ra tren dja ban tinh. Ddi vdi thdnh phfi Nha Trang ndi
TAP CHl KHOA HOC VA C O N G NGHf T H O Y LO'I SO 17 - 2013
KHOA HOC W » I . I J I t B f f f f T ^ ^ rieng, nhimg nam vira qua da dau tu rat nhieu cong trinh nham giai quyet tinh trang ngap lut trong ngi do de on dinh dan sinh tao tien de cho nen ldnh te phat trien. Tuy nhien, trong nam 2010 sau tran mua 1cm keo dai 2 ngay da gay ngap lut nghiem trong cho thanh ph6: 37 can nha sap, giao thong tren quoc lo IA bi tac nghen nhieu doan, cac cua ngo vao thanh ph6 Nha Trang gan nhu bi chia cat do ngap sau trong nuac, tai khu virc Dong Mudi thupc phuong Phudc Hai va Vinh Xuan xa Vinh Thai, mirc nuoc ngap toi 2 -2,5m va chay rit xiet. Udc tinh thiet hai toan Tinh nam 2010 len toi hon 400 ty d6ng, chito khoang 7% ngan sach nha nuoc tren dja ban tinh, day la mpt con so khong nho. Qua do co thi thiy r^ng giai quyet bai toan ngap lut do thi khong hi dl dang, ben canh mpt so giai phap co ban nhu tang kich thuoc cong thoat nuoc, nang nSn thi can CO mpt so giai phap t6ng th^, lau dai.
Truoc thuc te do, bai bao de xuat mpt s6 giam phap eong trinh hiru hieu co thi duac trign khai tai Tp. Nha Trang di giam thilu ngap lut.
II. PHirONG PHAP NGHIEN ClTU, CACH TIEP CAN:
2.1. Phu-ong phap nghien cihi
Phuong phap dieu tra, khao saf, ke thiia, phan tich tai li^u:
Dieu tra, khao sat hien trang he th6ng tieu thoat nuac Tp. Nha Trang.
• Do dac, thu thap chuSi s6 lieu khi tupng thiiy van TP. Nha Trang.
Dieu tra xa hpi hpc, vit lu.
Ke thira cac de tai, du an truac kia co lien quan iin muc tieu dS tai.[l][2][3]
Phuong phap mo hinh toan: Lap cac mo hinh toan mo phong/du bao diln biln ngap lut trong tat ca eac trang thai thoi tilt img voi cac giai phap khac nhau tren pham vi toan vimg nghien ciiu (VNC) va lan can lien tuc thoi gian dai vol cac s6 lieu diu vao khac nhau.
Sir dung cong nghe GIS: GIS phat triln tren CO so ke thira cua nganh Ban d6 hoc (Catorgraphy), cong cu tinh toan tu dpng tin
70 TAP CHl KHOA HQC VA C O N G N O H E T H O Y LC^I S 6 17 - 2013
hpc (informatic). Kit qua tinh toan ling voi cae giai phap khae nhau tir nghien curu nay se duae phan tich dU lieu khong gian va quan trj diJ lieu tren nen tang eong nghe GIS. Dieu nay se giup cho ket qua duac trinh bay ro rang, khoa hpc va de hieu eho nguoi theo doi. [3]
2.2. Cach tiep can
(i) Tiep can ke thira co chpn lpc tri thiie, kinh nghiem va ea sof dir lieu, phat trien eae kit qua nghien cim da co va tiep thu cong nghe lien quan den de tai.
(ii) Tiep can tich hpp eac khoa hpc cong nghe.
(iii) Tiep can he th6ng, toan dien va tong hop.
(iv) Tiep can thuc tiln.
(v) Tiep can he kinh tl - sinh thai - moi truang - phat triln bin vung.
III. THU'C TRANG NGAP L^T 0 THANH PHO NHA TRANG
Thuc trang ngap lut a thanh ph6 Nha Trang the hien a Bang 1
Bdng
So TT
1 2 3 4 5 6
7
1. Thdng ke cdc diem ngdp Nha Trang [6]
Diem ngap
Khu dan cu Duong D?
Duang Di$n Bien Phu - Khu dan cu Nam Hon Kho - Lans SOS Khu v\rc Chg Bau - phuOTiE VTnh Tho Khom Quoc Tuan - Lac Long Quan - Au Co Khu Quan Tran - Tran Quang Khai Khu vuc duong Le Thanh Ton (doan tir Ngo Gia Tu den Trin Phu) Khu Nguyin Trai - Huynh Thuc Khang - De P6
lut tgi thdnh pho
2010 Do sau
•"gap (m) 0,5 0,7 1 0,7 0,7 0,6
0,6 2011,
2012 Do sau (m) 0,2 0,5 0,7 0,3 0,3 0 , 3 - 0,5 0,5
I KHOA HQC" CONG NGHE
8 9 10 11
Khu vifc duong Nguyin Diic Cinh
Khu vvc dii6ng Vo Thj Siu, phudng VTnh Truorafi
) a VTnh Thai, phucmg Phu6c Hii Phudng Ngpc Hi?p
0,6 0,6 I,I 0,95
0,3 0,5
IV. NGUYEN NHAN N G ^ LUT THANH PHO NHA TRANG
Dja hinh: Tp. Nha Trang nam d phia dong Dfing bdng Dien Khdnh - Nha Trang, dia hinh thdp trung d phia tdy va cao dan ve phia dong (khu trung tdm gidp bien). Dieu nay giup cho todn bO khu vuc thdnh phfi khfing bi dnh hudng ldn bdi trifiu cudng, tuy nhifin nd lgi dnh hudng den viec thodt nudc tu nhien theo dja hinh ra phia bien, tgo nen mpt vimg thap triing li nudc, chgm tieu thoat d phia tay thanh phfi. Hon nfla, nd ciing gay khd khdn cho viec thiet kfi cao trinh dat tuyfin ong thodt nuac, dam bdo dp doc dan ra tdi cfla xd phia bifin.
Mpt sd khu v\rc cd dia hinh thap c\ic bp hodc ndm xem giua nhiing ngpn nui cflng la nguySn nhan thudng xuyen bi ngdp l\it [6]
Mira: Do ndm trong vimg khi hdu nhipt ddi gio miia, nSn lugng mua hdng nam tuong doi ldn (1500 ^ 2000ram/nam), nhung phdn bd khfing deu theo thdi gian, chu yfiu tgp trung vao miia mua bdo. Khi mua vdi cudng dp khoang tren 30 mm, trong thdi gian ngdn thudng gdy ra nggp flng. Neu mua vdi cudng dp ldn hon, thdi gian mua tap trung ddi hon thi muc dp ngap flng cdng nguy hiem hon.[2]
Lu sfing Cai: Thanh phfi Nha Trang ndm d hg luu luu vyc song Cai. Ciing giong nhu ddc diSm ciia cac luu v\rc song vung Duyfin Hdi Mifin Trung, Iuu vuc song Cai cd dia hinh nhiSu d6i nui, di^n tich nho, hpp chgy dai theo sfing, song suoi thi cd chifiu dai ngdn va doc.
Do vgy khi cd mua ldn keo ddi thudng tao ra lu quet, lam cho muc nudc song dang nhanh, gay thipt hgi nghiem trpng vfi ngudi vd cua.
Theo nghifin cflu gan ddy, khu vyc bj ngdp nhifiu nhit la cac phudng Ngpc Hipp, Phudc
Long, Phudc Hdi va VTnh Hdi.[2]
Hf thong thodt nirdc: Hp thdng thodt nudc d Thanh pho Nha Trang thudng dupc gpi la hp thong thodt nudc mua nhung do mpt phdn thi^t kfi va thi cong khonjg dflng qui cdch, phdn khdc thi do chdt lupng rat kem do xdy dung dd qud lau. Vi vay nd vfla khong dam bao yfiu cau vfi sinh moi trudng khu ddn cu, vfla khd khdn cho cdng tac qudn ly vdn hanh. Trong tfing sd 55,54 km cong ngdm hifin cd thi khodng 10,3 km dupc xay dimg trudc ndm 1975 nay da xufing cap nghiem trpng. Phdn ldn (trfin 30km) dupc xdy dung sau nam 1995 nhung ch^t lupng cung rat thdp.
To chiJx, quan ^ vain hanh [6]: He thong thoat nudc mua va nudc thai chung nhau, cdn trd toe dp tifiu thodt khi mua xuong gay ra ngdp ung vd lam 6 nhiem moi trudng.Vipc quan ly he thdng thodt nuoc kem, cdc dudng ong, kenh rach khfing dupc tu sfla, nao vet kip thdi ldm dnh hudng d^n khd ndng tifiu thodt. Y thflc bdo ve h?
thfing tieu thoat cfla cpng dfing thap nhu xd rdc gdy ldp cdc h6 ga, bjt hfi ga ngdn mfli hoi, xdy dung 1^ chifim kfinh muong thodt nudc, xa rdc va cac loai chat thdi bira bai gdy tde nghen vd fi nhiem mfii trudng [6].
V, CAC GIAI PHAP GIAM THIEU NGAP LVT 5.L Phan vung tiSu nird'c cho Tp. Nha Trang Vi?c phdn vung tifiu thoat nudc la rdt quan trpng vd thuc tfi cho thdy cac gidi phdp chong nggp cho thdnh phd Nha Trang phy thupc rdt nhieu vdo vifc phan viing tieu thodt nudc. Do vgy cdn phai cd cac nghifin ciru sdu hon vfi nfii dung ndy lam CO sd khoa hpc cho cdc nghien cflu vfi gidi phap cfing trinh phdng chong ngdp doi vdi tung khu vyc cy the.
a) Tieu chi phdn viing [4]
- Difiu ki^n dia hinh.
- He thdng thodt nudc mua hipn hihi vd qui hogch trong tuong lai.
- Hifin trang va nguyen nhdn gdy ngdp.
- Do thj hda hi^n tai vd tuong lai.
- Ranh gidi hdnh chinh, luu vyc song kfinh.
T*P CHl KHOA HQC VA C O N G NGHE T H O Y LQ\ S O 17 - 2013 71
KHOA HOC CONG NGHE - Hien trang va nguyen nhan gdy ngap.
- Do thi hoa hien tai vd tuong lai.
- Ranh gidi hanh chinh, luu vuc song kenh.
b) Phuang dn phdn viing
(1) Viing 1: gfim cac phudng Van Thdng, Phuong Sai, Phuong Son va mot phdn Ngoc Hiep. (2) Viing 2: gom cac phudng Van Thanh, Xuong Huan va mot phdn Loc Tho. (3) Vung 3: gom cac phudng Phuoc Tan, Phudc TiSn, Phudc Hai, Tan Lgp, Phudc Hoa va mot phdn Loc Thp. (4) Viing 4: gom cac phudng Vinh Nguyen, Vinh Trudng, Phudc Long va mpt phdn Phudc Hoa. (5) Viing 5: gdm mpt phdn Vmh Thg, VTnh Phudc. (5) Viing 6: gfim mpt phdn VTnh Phudc, Vinh Hai, VTnh Hoa. (7)Viing 7:
gom mpt phdn VTnh Hai, VTnh Thp (8) Viing 8: gom mot phdn cac xa VTnh Hiep, VTnh Thdi, pham vi tir phia Bdc dudng Phong Chau den dudng 23 thang
10. (9) Vung 9: gfim cac xa Phudc Dong, mpt phan Phudc Thuong va mpt phan VTnh Thai, 5.2 GL\I PHAP KIEM SOAT VA CHONG LU Ttr THUONG LUtJ SONG CAI VA CAC PHU LUtI
5.2.L Bien phdp cdng trinh
- Giai phap 1: Phan lu song Cai mpt phan qua song Quan Trudng va song Tde qua viec thuc hien noi dai song cau Be ra song Cai gan Vo Cang.
BAN D O PHAN V U N G Tteu THOAT NUdc KHU W C Npi THANH THANH PHO NHA TRANG
Hinh 2: Bdn do phdn vitng tieu thodt nudc khu vuc ndi thdnh Nha Trang
- Giai phap 2: Ke doc sdng Cdi ung vdi cao trinh chong lli.
5.2.2 Ket qua tfnh todn giai phdp 1
Hinh 3' Thiet lap mang ludi viing nghien ciru
Luu lugng thupng luu sdng Cdi dupc ldy ldn Bfi rpng sdng cau Bfi dogn nfii dai lan lupt luot vdi tdn sudt 1%, 5%, 10%. dupc ldy B=30m, 35m, 40m vdi chifiu sau H =
4m (Xem hmh 3).
72 TAP C H [ K H O A HQC VA G O N G NGHf THlJY LOI SO 17 - 2013
I KHOA HOC CONG NGHE
Bi r§ng kenh (m) B=30m B=35ni B=40m
Bdng 2: Ket qud lui. lugng dhgluu sdng Cdi vd sons Cdu Be Liru liTQUg thirtfng luu (m'*/s)
(JTL vai tin suat l u i % OIL vcri tan suit lu 5% | QTL voi tin suit lu 10%
Luu lugng cic nhanh o' ha luu QHLSC
3850 3734 3592
QsCB 876 992 1134
QHLSC 3109 2995 2919
QsCB 682 796 872
QHLSC 2673 2607 2541
QsCB 627 693 759 Trong dd: QTL: luu lupng d thupng luu
QHLSC: luu lupng d hg luu song Cdi.
QSCB: luu lupng d song Cau Be.
Vdi vi$c phdn lu song Cai qua sfing Cdu Be de v£ song Qudn Trudng, luu lupng lu chdy vfi hg luu dd gidm mpt each ro ret. Sau khi duge phdn lu, lu sfing Cdi vdi tdn sudt 1% {4726 m^/s) dd gidm chi cdn ung vdi tin suat lu Id 10% (3850 m^/s) d hg luu sdng Cdi, tuong ung gidm gan 22% vdi be rpng song Cdu Be 30m.
Con vdi be r0ng 40m thi luu lupng xufing hg luu son^ Cai chi cdn 3500 m^/s. Dfii vdi kich ban lu tdn su4t 10%, luu lugng lu vfi ha luu sfing Cdi chi cdn 2673 m'^/s vdi be rpng song Cdu Bfi B=30m va cdn 2541 m^/s vdi bfi rfing sfing Cdu Be B=40m.
5.2.3 K^t qua tinh toan giai phap 2 Tdn suit lu duge ldy tinh toan la 1%.
Xdy dyng 3 phuang dn thifit k^ cao trinh ke (Xem hinh 3):
Kich bdn 1: Cao trinh ke tu 2,5 m tai cdu Hd Ra den 3,0 m tgi c4u dudng sdt.
Kich ban 2: Cao trinh ke tfl 3,0 m tgi cdu Ha Ra den 3,5 m tgi cdu dudng sdt.
Kich ban 3: Cao trinh ke tu 3,5 m tgi cdu Ha Ra dfin 4,0 m tgi cdu dudng sdt.
Bdng 3: Ket qud tinh di$n tich nggp (ha) giita cdc phuang dn
Kjch Mn KBI KB2 KB3
D$ sSu nggp (ha) 0-0,5
502,043 426,645 0
0,5-1 467,884 399,862 0
1-1,5 344,782 254,564 0
1,5-2 91,245 76,541 0
>2 10,463 8,964 0
Hinh 4: Dien lich ngdp lut bdi IS sdng Cdi vdi Hinh 5: Dien lich ngdp lut bdi IQ sdng Cdi vdi ldn suat 1% ciia KBI tdn sudt 1% ciia KB3
T*P CHl KHOA HOC VA C O N G NGHE THClY LO'I SO 17 • 2013 73
KHOA HOC CONG NGHE Qua bdng tren cd thfi thay vdi phuong an 1 (KBI) cao trinh ke tfl 2,5 m - 3 m, tong dien tich ngdp hon 14 trifiu m^ trong do difin tich nggp tfl 0 - 0,5 chifim nhieu nhat, xdp xi 5 trieu m^. Vdi phuong an (KB2) cao trinh ke tfl 3 m - 3,5 m, dien tich cd ngap cd gidm tuy nhifin khdng nhifia van cdn tren hon 11 trifiu m^ bi ngap, ly do cao trinh myc nudc tai song Cdi ung vdi t ^ sudt lu 1% cao hon 3,5 m tgi ha luu cdu dudng sdt va gay ra nggp. Tuy nhien vdi phuong dn 3 (KB3) cao trinh ke tfl 3,5 m tai cdu Hd Ra va 4 m tai cdu dudng sdt da ngdn chgn duge lu tu song Cai, cao trinh muc nudc sdng Cai thdp hem cao trinh ke duge de xudt vd mo phdng.
5.3. Giai phap quy hoach phat trien h | thong ho dieu hoa nhdm giam thilu ngap lut Hieu qud chimg cfla viec xdy dyng cac ho dieu hda se gdp phan gidi quyfit van dfi thyc trang tifiu thoat nudc Thanh pho nhu tdng kha nang thoat nudc trpng luc, gidm qui mfi tram bom tifiu, gidm khoi lugng san ldp nfin, gidm d nhiem mdi trudng vd cai tgo canh quan moi trudng sinh thdi. Tuy nhifin, do mat dp ddn cu phdn bfi hien nay khd day dac nen viec bd tri xdy dyng cdc hd difiu hda khd khd khan vd qui hoach cdc dd thi mdi chua chu trpng gidnh qui ddt xdy dyng hd mgc du difin tich mdt nudc
khong dam bao cho tifiu thodt.
5.3.L Dixudt v/ tri xdy dtpig hd diiu hda a. Cic tieu chi lya chpn vi tri hfi dieu hda - Cd cao dp dia hinh phu hgp dfi nudc mua chdy tdi hfi vdi luu lugng ldn nhdt.
- Ddng chdy thu duge tu cac tuyen cong cap 2, kfinh rach chay tdi hd cd thai gian ngdn nhdt.
- Ddng chdy vao vd ra hfi la hpp ly nhat.
- it phai di ddi, phu hgp qui hoach sw dung ddt.
- Kit hgp cong trinh xung quanh, cdi tgo ty nhien, tao cdnh quan mdi trudng sinh thai.
b. Kfit qua dfi xudt vi tri cac hd difiu hda Khu vuc gdn trudng trung hpc phd thdng Hemann Gmeiner Nha Trang.
- Khu vuc sdn bay Nha Trang, giap dudng Biet Thu vd Nguyen Thi Minh Khai.
5,3,2, Tinh todn khd ndng tiiu thodt nudc c&a hd diiu hda
Lugng mua duge dua vao tinh toan cd tan sudt la 10%.
Dung tich hd difiu tifit duge dua vao tinh toan ldn luot la 5000 m^ (PAl), 7000 m^ (PA2) vd 10.000 m V A 3 )
•''t:^
Hinh 6:Hien trgng ngdp lut chua cd hd diiu tiet Hinh 7 Kel qua ngap lut khi thuc luen PA I
74 TAP CHl KHOA HOC VA C O N G NGH? THCIY LQ[ SO 17 - 2013
Hinh 8: Ket qud nggp lut khi thuc hien PA2 Qua ket qud mfi phdng cd thfi thay rdng, vipc xdy dyng hfi dieu tifit d 2 khu vyc tren da gidm thifiu nggp lyt ddng kh tgi cdc vi tri nay.
Hd diiu tiit 1 (Vinh Hdi): Khu vyc ngdp lyt quanh lang SOS ca ban dd duge gidi quyet.
Dien tich ngdp lyt cfla cd tieu vimg 7 da gidm
\hi lupt 22%, 25%, 30% cho PAl, PA2 vd PA3. Ben canh dd, d^ sdu nggp tgi khu vyc nay cung da gidm, nhflng noi cd dd sau nggp ldn nhu khu vyc lang trfi SOS hay khu vyc quanh Mai Xudn Thugng da gidm ro rpt.
Hddiiu tiit 2 (Khu sdn bay Nha Trang): vdi sy dong gdp hh difiu tiet, di^n tich ngap cflng nhu dO sau ngdp da gidm hdn, dac bipt Id khu vyc Tran Quang Khdi, Hung Vuong. Di^n tich nggp lyt cfla ca tifiu virng 3 ldn lugt giam 15%, 17%, 20% cho PAl, PA2 vaPA3.
Ngoai chfle ndng chinh la gdp phdn gidm thieu nggp lyt, h6 dieu hda cdn nhdm cdi tao cdnh quan, moi trudng, la difim vui chai cfla ngudi dan dfi thj. Ngoai ra hfi difiu tifit cflng giup cho myc nudc ngam tgi khu vyc tdng lfin, giam do nhiim m ^ cho tang nudc ngam.. Ve ldu ddi se nghien cim phuong dn chuyen nudc tfl mpt sfi
Hinh 9:Ket qud ngdp l\it khi thirc hi?n PAS khu vyc dfin cdc ho nay.
5.4. LTng dung 1^ tfau^t thu tru nirorc mtra de giam thieu ng^p lyt cho TP. Nha Trang 5.4.1. Cdi thi^n kha nang thdm bi m^t Dfi tdng khd ndng thdm nudc cfla be mdt, &h xudt nhflng bien phdp sau:
Giam t6i da dipn tich be tong hda khfing cin thifit.
Tang dipn tich tham cd, cdy xanh d cdc co quan, xi nghipp, cong vifin vi thyc vdt cd the hflt nudc vd gifl nudc rat tot.
Dfii vdi ldi di ddnh cho ngudi di bO, thay vi sfl dung bfi tfing hoac gach Idt kin nfin dung ggch xfip ho|c rdi sdi dfi tdng khd ndng thdm hut.
Dudi day la mpt s6 logi kfit cau bdng ggch ty chen bfi tong due sdn, cd tinh ndng thodt nudc, la kfit cdu kha thi dp dyng dupc mfit each hipu qua d difiu kipn Vipt Nam, cho nhifiu hgng muc nhu via hfi, mdt dudng, bdi do xe, cfing vifin...
TAP CHl KHOA HOC VA C C N G NGH? T H O Y L(?l SO 17 - 2013 75
KHOA HOC CONG NGHE
i t t t
^ 4 4 4 4
HinhIO: He thong kieu 1- Thodt nudc thdng dung hodn todn
Hinh 11: He thong kiiu 2- Mdtj)hdn tham thdng dim^
mot plidn duac ddn ngang den cdc vi tri trie nudc
50/60/SOnm-
?W?»HS? . 250-450f™ii *
of 20-5niin- clean aggregate
Permeable Sloda
Hinh 12: He thong kieu 3- Hodn loan khdng cho Hinh 13: Cdu tgo dien hinh ciia lap phu mat nuac thdm phia dudi, chi thodt ngang ve nai chi dinh thodt nudc
Hinh 14: Ket <
d Tp. Nha Trang, nai dia chat nfin dat nhifiu khu vyc la cat, viec dp dung cdc kfit cdu nay m$t each dflng each va phfl hpp se dem lgi gid tri r^t ldn:
> Giai quyfit duge mpt phdn thodt nudc khi mua ldn, vi khong thfi cfl tdng khdu dp cfing thoat nudc lfin.
> Tigt kipm duge kinh phi cho phdn he thfing thodt nudc.
':du gach tu chen
> Giu duge dp im cua nSn dit va khong khi trong khu vvrc, t?io s\f mat me, thuan lgi cho cay c6 ph4t trien.
> Bo sung mot phan lugng nudc ngim.
> Voi ket cau mat ducrag b§ng g?ich tu ch6n, ngu duge thiet ke t6i im se re hon so voi giai phap bS tong nh\ra, do tai trpng va luu lugng xe trong khu dan cu khong 16n lam va da so phai ding kSt ciu phil mat be tong nhua vcri
76 TAP CHl KHOA HOC VA CONG NGH? THCIY L ( ? I SO 17 - 2013
I KHOA HOC
chiSu diy toi thieu theo quy trinh thiet ke ao kich ban tang dien tich co kha nang thim nuac ducmg mem.
a) Tinh toan ng^p lyt cho gidi phap tang di^n tfch thim nuo^c
Tinh toan, danh gia dien bien ngSp lut vdi cac
cho khu vuc noi thanh thanh ph6 Nlia Trang vai he so tham gia thilt 0,4 cho cac khu vuc kha nang thim nudc. Cu thS, dien tich thim nuac tang lin lugt 10%, 20% va 30%.
Hinh 15. Ngdp hll hien trang do nnra vdi Idn sudi 10%
Hinh 16: Ngdp lui do mua vdi Idn sudi 10%
vii PA I
Hinh 17: Ngdp lut do mua vdi ldn sudt 10% Hinh 18: Ngdp iul do mua vdi tdn suat 10%
vdiPA2 vdi PAS
b) Nh^n xet: thim len them 10%, tu dien tich ngap han 2,8 Qua ket qua tinh toan co thS thiy ring, dien tich trifu m^ xudng c6n 2,2 trieu m^. C6n n6u tang nglp da giam iin hon 21% khi tang dien tich dien tich tham lin lugt len 20% va 30% thi dien
TAP CHl KHOA HQC VA CONG NGHf T H j Y LO'I SO 17 - 2013 77
I KHOA HOC
tich ngdp lin lugt chi con 1,5 trieu m^ va hon qua dang kS khi tang dien tich thim bl mjt d6i 900 ngin ml Tit'ket qua tren co the thiy su hieu vcH ng?p Ivt cho Tp. Nha Trang.
Hmh 19: Biiu do diln bien ngdp giUa cdc phuang dn
Bdng 4: Diin tich mdp (ha) eiOa cdc phuang (ift
Phuong an HT 10%
20%
30%
Do sau ngap (m) ., 0-0,5
258,930 207,858 144,197 83,483
0,5-1 22,522 14,144 10,21"5 6,414
1-1,5 7,650 5,120 3,832 2,667
5.4.2. Chong ng^p bdng cac bifn phap chira niro^c t^m thM
Sfl dyng cdc khu vyc chuc ndng de chfla nuac mua tgm thdi trong npi thi la mpt trong nhung giai phap hiiu hieu ehfing ngdp do thi vi du nhu sdn cd, bai ddu xe, cong vifin, san trudng,... Mpt phdn lupng nudc trong cdc cong tieu thoat nudc se dupc chuyfin dfin nhung nai khu chfla nay khi qua khd ndng tifiu thoat cua cdc cfing ndy. Sau ddy Id cdc budc thuc hien cho cdc nha quan ly, CO quan chfle ndng lien quan:
Cac buo'c thyc hifn [5]:
- Xdc djnh nhiing vi tri phii hgp cho viec chua nudc tgm thdi.
Cdn chu y khi xdc dinh nhflng vi tri phu hgp cho
vific chfla nudc cdn phdi luu y cac difim sau:
- Nhflng vi tri ndy la tuang ddi khong thudng xuyfin chua nudc ngdp.
- Nhiing vi tri nay duge ldy tii nhflng khu chfla nang khdc nhau.
- Nhflng vi tri ndy khi dang chua nudc nggp tM cd thfi se khong duge sfl dung trong thdi doan ngan.
- Tinh todn do sdu ngdp ldn nhdt cho moi vf tri do.
Chifiu sdu ngdp cho phep cfla cdc vi tri tuy thupc vdo tinh hinh cu the, bfin canh do cd the tham khdo cuon cdm nang "Thanh pho va ngdp lyt: Hudng din vfi Quan ly rfli ro ngap lyt do thi tfing hgp cho thi ky 21" cfla ngdn hang The gidi WB, theo bang dudi ddy:
Loai Bai ddu xe Duong hem (phu) Khu giai tri th8 thao Sdn trudng Sdn vgn dpng Cfing vien Khu cong nghi?p
M o t a
Dupc su dung tam thdi. Can gioi han do sdu ngap cho phep de khong anh hudng den phuong tipn di lai va tai san Cijng cd the dupc sfl dung nhung han che
Cdc loai sdn cung ngoai trdi (xi mdng) nhu bdng rfi, tennis, sdn bong dd mini
San tmdng cung la noi chiia mpt lupng nudc khd ldn, tuy nhien cdng can phai tinh toan den an toan cho hpc sinh.
Day cfing la mpt trong nhung noi cd the chfla nufifC dupc khoi lupng Idn
Khu vyc nay cd the chfla lupng nudc Idn hgn che dupc ngap lut d ha nguon
Di?n tich chiia khu vyc nay khong nhifiu. Ben cgnh dd can luu y cho vi?c lya chpn dia di€m de tranh vi?c d nhilm
Chieu sau ngap Idn nhat 0,2 m
0,1 m
0,5 m - lm; neu khu nay vdn ddm bdo 0,3 m.
0,5 m - Im; neu khu nay van dam bdo 0,5 m - lm; neu khu nay vdn ddm bdo 0,3 m.
Ngudn: [5]
78 TAP CHl KHOA HQC VA C O N G NGHg T H O Y LO'I SO 17 - 2013
KHOA HOC - ifdc tinh the tich khu chda tgm.
Cfi th€ dua vdo chieu sdu nggp ldn nhdt ciing nhu dfl lipu dia hinh tai cac khu vyc chfla tgm dl udc tinh ihk tich chfla nudc.
-Xdc dinh chd tieu thodt cho khu trii.
Sau khi lfl lyt di qua tW cdc khu trfl nudc tam thdi cd the bom nudc ra cdc cong thoat, sfing kenh gan nhat, hoac cd the cho ty ngdm nhung thdi gian tifiu thodt se keo dai.
- Cdn xem xet nhitng vdn di an todn vd sii:c khoe trong khi xdy ra lU vd sau Id.
Budc nay cung vd cflng quan trpng \i ben cgnh nhihig gidi phdp gidm thifiu nggp lut tW giai phap cho vdn de an toan va sflc khoe cfla cpng dfing trong khi xdy ra vd sau lfl cdn hfit sflc chfl y nhu so tdn kip thdi, dpn dpp ve sinh sau lu,...
VI. KETLU^
Qua dieu tra cung nhu tinh todn thi cd 3
nguyfin nhan chinh gdy flng nggp cho Tp. Nha Trang: (1) mua cuong d0 ldn (ddc difim mua d thanh ph6 la mua doi Iuu), (2) lu thugng nguon do vfi va (3) nggp cyc bp bdi dia hinh.
Ngodi ra, CO sd h^ tdng cfla hp thdng tifiu thoat nuoc trong thanh ph6 khong thfi dap flng dupc kip thoi nhu cdu tieu thodt do t^c dO phdt trien kinh tfi xd h^i trong nhflng ndm ghn day, dd cung Id nguyen nhdn lam trdm trpng them tinh trgng ngdp ung cfla TP hifin nay.
Tren co sd lgi dung quy ludt ty nhifin cfla ddng chdy ciing nhu ddc dilm ty nhifin, hien trgng dja hmh cunp nhu bdn qui hogch tong thfi cfla thdnh ph6 dfin nam 2025, bdi bdo dd dl xuit duge cdc gidi phap cong trinh nhu phdn lu, vj tri xdy dyng ke, ho cdng vifin dilu tifit,...nhdm gidi quyfit ca bdn tinh trgng ngdp tren dia ban Tp. Nha Trang, gdp phan cai tgo moi trudng nuac ddp flng yfiu ciiu phdt triln kinh tfi - xd hpi, ndng cao ddi song ngudi ddn trong vflng.
Mpt so gidi phap cong trinh phfl hpp cho chong ngap Tp. Nha Trang duge de xuat.
T A I U ? U THAM KHAO
[1] TS. Nguyen Huu Nhan, 2001. Di tdi "Xay dymg bdn dd nggp lyt ti I? 1:10.000 hg luu sdng Cdi Nha Trang".
[2] Sd Nfing nghi?p vd PTNT tinh Khanh Hod, 201 X.Di^dn "Lgp bdn dd nggp lut khu vuc sdng Dinh Ninh Hda vd sdng Cdi Nha Trang "
[3] ThS. Phan Mgnh Hiing, 2011. Lugn vdn thgc sT "Cdc dge tlnh cua rdi ro nggp lift cdc dd thf ven bien ".
[4] PGS. TS Tdng Dflc Thdng, 2011. Di tdi cdp Nhd nudc "Nghien cuu cdc gidi phdp chdng nggp Tp.
Ho Chi Minh"
[5] Ngan hdng The gidi WB, 2012. Cam nang "Thdnh phd vd nggp lut: Hudng ddn vi Qudn ly riii ro nggp Itft dd thi idng hgp cho thi ky 21"
[6] Nguyen Thj Phuong Thao, 2013. Chuyen de "Nguyen nhdn nggp dng Tp.Nha Trang".
TAP CHl KHOA HOC VA C O N G NGHE T H O Y LQ\ S O 17 - 2013 79