N G H I E N C t r u C A C TAI B I E N T H I E N N H I E N d DAI D O N G B.\NG NXN BIEN THL^A T H I E N H U E
NGUY£N THAM Trudng Dai hoc Suphgm - Dgt hoc Hue
PHAN ANH HANG Trudng Dgi hoc Phu Xuan. Hue
Tom tat: Dai dong b ^ g ven bien Thira Thien Hue la noi rat nhay cam vdi thien tai \ a cac tac dpng cua bien doi khi hau. Hang nam, tinh Thira Thien Hue noi chung va dai dong b5ng ven bien noi rieng phai ganh chju nhung hau qua nang ne do thien tai gay ra. Dac biet trong ohiiTig nam gan day, cac tai bien thien nhien nhu bao Idn, )u lut, xdi id bd sdng, xdi Id bd bien, ban han, xam nhap man, muc mrdc bien dang... xay ra voi cudng dd va tin suit tang len dang ke, gay Idn that Idn \~e t ^ mang va tai san cua ngudi dan, xam bai den Quan the Di tich Cd do da dugc uSiESCO cong nhin la di san
\aa hoa cua nhan loai va anh hudng nghiem trpng den mdi trudng sinh thai.
I. DAT VAN DE
£)dng bing ven bien Thira Thien Hue chiem khoang 16% dien tich toan tinh, phan bd thanh dai hep dgc theo ven bien \ a dugc hinh thanh do qua trinh bdi dip ciia sdng va bien. Do cao tuyet ddi tir I5-10m trd xuong, bao gdm bo phan ddng bang ddi Huang Thiiy, Phu Vang, Huang Tia, Phu Ldc; ddng bing tich tu nhieu ngudn goc; cac trang cat noi ddng Phong Dien, Quang Dien, Phii Vang; cac dang dja hinh dam pha va cac cdn dun cat ven bien.
Do dia hinh thip, la ha luu ciia cac sdng ngan doc, vdi luu lugng nude Idn, ddng bang dl bi ngap lut vl mua mua. han han va xam nhap man vao thdi diem it mua. Ngoai ra, hoat dpng xam thuc, xdi Id bd sdng, bd bien thudng xay ra. Dac biet lien tilp trong nhirng nam gin day, do tac ddng cua bien ddi khi hau toan ciu, cac tai bien thien nhien da xay ra vdi quy md va cuimg do rat Idn vdi sire tan pha ngay cang ac liet da gay nen nhung hau qua nang ne ddi vdi sir phai trien kinh tl xa hdi tinh Thira Thien Hue ndi chimg va dai dong bing ven bien ndi rieng. Bai viet nhim tim hieu hien trang cac tai biln thien nhien d dai ddng bang ven bien Thira Thien Hue (lii lut, xdi Id bd sdng, xdi Id bd bien, han ban, xam nhap man, muc nude bien dang), cac nhan to tac dpng gay tai biln thien nhien va de xuat mpt sd giai phip ban che tic hai do cac tai bien thien nhien gay ra d dai ddng bing ven bien Thiia Thien Hue.
Tap chi Khoa boc ^ a Giao due, Trudng Dai hoc Su pham Hue ISSN 1859-1612. S6 03(19V2011:tr. 27-37
2. HIEN TRANG CAC TAI BIEN THIEN NHIEN Ci DAI D 6 N G B A N G VEN BIEN THLTA THIEN HUE
Lii lut la mpt trong nhiing tai biln thien nhien xay ra phd bi6n va gay nhieu thi?t hai nhit d ddng bang ven biln Thira Thien Hui. Trong lich sir, da ghi lai nhiing nam lu cue Idn nhu: nam 1404 (md cira Hda Duin lin diu), nam 1498 (md ciia Hda Duan lin hai), nam 1811 (md ciia Vinh Hiln), cac nam 1822, 1844, 1950, 1953 (md lai cua Vinh Hiln), cac nam 1964, 1975,1983, 1990, 1995, 1996,1998, 1999 (md cira Hda Duin lin ba) [5].
Trong vdng 50 nim tra lai day, lu lut xay ra thudng xuyen han niia diu the ky trudc.
Theo sd lieu quan trie tir nam 1977 den nam 2010 tren sdng Huang, trung binh hang nim cd 3,5 tr$n lu Idn ban hoac bing miic bao dpng H, nam nhidu nhit cd 9 tran, nam it nhit cd I trin, trong dd cd 36% lii Idn va d$c bi?t Idn. Sd dot lu va dinh lu hang nam cd lien he khi chat chg vdi hi^n tugng ENSO. Nhihig nam chju anh hudng ciia El Nino nhu 1982,1987, 1991, 1994 va 1997 cd dinh lu thip; nhiing nam chiu anh hudng ciia La Nma sd dgt lu va dinh lu Idn hon ro ret nhu nim 1995, 1998 va 1999. Sd lieu quan trie cho thiy, sy bien ddi muc nude dinh lu cao nhit dien ra theo mot chu ky nhat dinh:
khoang 4 - 6 nam cd lu vira va nhd thi cd 2 nam lii Idn lien tiep nhu: 1983-1984; 1988- 1989; 1995-1996; 1998-1999. Mdt s6 trin lu ti8u bilu cd dinh lii cao nhit d sdng Huang t^i Kim Long nhu sau: 1953: 5.48m; 1975: 4.72m; 1983: 4.88m; 1990: 4.56m; 1995;
4.64m; 1996: 4.55m; 1999: 5.81m; nam 2009: 4,57m.
Hau nhu nim nao muc nude d cac sdng chinh cung deu len bao dpng IE, vi vay toan bd cac thdn xa deu bj chia cat. Neu nhu d mien niii vdi dac dilm lii len nhanh va nit nhanh, d ddng bang yen bien Thira Thien Hue, lu thudng xuit hien sau nhung thdi gian ngap lyt keo dai, trim trpng hem nhilu so vdi khu vuc ddi nui.
2.2. Xdi Id bd song
Xdi Id bd sdng chi xay ra d phia bd 1dm ciia cac doan sdng cong hay tai cac vi tri bd sdng chiu tie dpng true dien ciia ddng chu luu va xiy ra chii ylu trong nhiing thdi ky lu Idn.
Tren h^ thdng sdng Huong: Theo kit qua khao sat, tren he thdng sdng Huong hi^n nay cd 31 diem xdi Id, trong do doan sdng chay qua vimg ddng bang ven biln cd 21 dilm xdi Id chiem 67,7% tdng sd diem xdi Id.
Tren ddng chinh sdng Huang: Xdi Id phia bd phai sdng gdm cac vi tri: thdn Luang Quan - Thuy Bilu - TP Hui (500 m); Ddtig Phudc - Thuy Bilu - TP Hui (500m);
phudng VT D9 - TP Hui, dpc theo hai ben cdn Hin (3.300m); phuong VT Da - TP Hui, dpc dudng Nguyin Sinh Cung (2.100m); Thanh Tien - Lai An - Phu Mau - Phii Vang (1.500m); Hoa An - Phu Thanh - Phii Vang (dai 500m).
Xdi Id phia bd trai sdng gdm cac vj tri tai thdn Long Hd Thugng - Huong Hd - Huang
NGHIEN CUU CAC TAI BIEN THIEN >4HIEN 6 DAI DONG BANG VEN BIEN TT HUE
Tra (150m); Xudc Du - Huang Hd - Huang Tra (dai 3.000m); chua Thien Mu - Huong Long - TP Hui (600m); thugng luu ciu Bach Ho - Phudng Kim Long (1.500m); Bin Me (300m); phudng Phu Cat va phudng Phii Hiep - TP Hui (2.300m); Thanh Phudc - Thuan Hoa - Huang Phong - Huang Tra (I.900m).
Xdi Id dau cdn Trieu San, thupc Huang Vinh - Huong Tra, dai 750m.
Tren song Bd: Xdi Id phia bd phai sdng gdm cac vi tri tai thdn Lieu Cdc Ha - Huang Cin - Huang Tra (700m); Thanh Xuan - Huong Viet - Huang Tra (200m).
Xdi Id phia bd trai sdng gdm cac vi tri tai tiidn La Van Thuang - Quang Thp - Quang Diln (2.000m); Duong San - Quang Tho - Quang Diln (350m); Phong An - Phong Diln (3.000m).
Vi tri xdi Id ca hai ben bd sdng thudc Ap Phd Nam - Quang Thp (600m).
Xdi Id d diu cdn Ha Lan thugc Bac Vpng Tay - Quang Phii - Quang Diln, dai 150m.
Tren sdng 6 Liu: Phong Thu - Phong Diln, nhilu nai xdi Id sau din 15-20m, dai 2.000m.
Tren sdng Tmdi: Ddng Xuan - Lgc Dien - Phii Ldc, nan khai thac cat san ngay cang gia tang khien nguy ca xdi Id cang trd nen nghiem trpng, chieu dai doan xdi Id 200m.
Tren song Bii Lu: Canh Duong, Ddng An, Phii Hai - Ldc VTnh - Phii Ldc, cd noi bd sdng bi khoet sau 60-70m, chieu dai doan sat Id 300m.
2 3 . Xdi Id bd biln
Hien nay, hien tugng xdi Id bd bien Thira Thien Hui xay ra thudng xuy8n, phiic tap va ngay cang gia tang, nhit la doan bd tir Hai Duong den Phii Thuan. Xdi Id bd bien diudng xay ra vao mua ddng (tir thang 8 den tiling 3). Tir thang 9-12, tdc do xdi Id xay ra manh nhat, d^c biet trong thdi diem cd gio miia Ddng Bac ho5c ap thap nhiet ddi hoat ddng.
Toe do xdi Id lin sau vao dat lien trung binh nam kha Idn va dugc chia lam 4 cap [I]:
+ Yeu: cd ^ dp lin sau vao bd trung bmh dudi 5m/nam (Dien Hda, Phong Hai thupc huyen Phong Diln; Quang Cdng - Quang Dien; Phit Thuan, Phii Diln - Phii Vang; Vinh Hai, Vinh My - Phii Ldc).
+ Trung binh: cd tdc dp lin sau vao bd trung binh 5 - 1 5 m/nam (Thuan An - Phii Vang; Lgc Hai - Phii Ldc).
-1- Nhanh: cd tdc dp lan sau vao bd tmng binh dudi I5-30ni/nam (Quang Ngan - Quang Diln; cira Thuan An - Huang Tra; Phu Hai, Vinh An, ciia Thuan An - Phu Vang; Lgc Vinh - Phii Ldc).
+ Rit nhanh: cd tdc do lin sau vao bd tnmg binh tren 30m/nam (Hai Duang - Huang Tra, Vinh Hien - Phii Ldc).
Trong qua khii, cd nhung dgt han nang nhu 1977 (nang h^n 41 ngay tir 25/05 din 04/07), 1993-1994,1997-1998, 2002.
Dgt han nim 1993-1994, lugng mua do dugc tu thing 1 din thing 8 nam 1993 chi bing 58% lugng mua tnmg binh nam cimg thdi ky, nam 1994 chi bang 49%; nhi?t dp cao nhit trong hai nam 1993-1994 la 39 din 40''C.
Nam 1998, han han lai xay ra kha nghiem trgng, nhiet dp cao nhit tuyet ddi do dugc trong cac dgt nang ndng d Hue la 39,5''C, muc nude tren cac sdng thing 7, thing 8 thap han trung binh nhilu nim td 0,2 din 0,3m. Nam nay cd sd ngay gid Tiy khd ndng Idn nhit, lien quan din su xuit hien El Nino.
Trong dgt ban 2002, nude min vugt qua Van NiSn ISn tdi phi Tuin lam nhilu nhi miy, xi nghidp phai ddng cira nhilu ngay, anh hudng khdng nhd din kinh tl ciia tinh.
Gin diy, Thira Thien Hue lai phai ddi m^t vdi nhOng thach thuc Idn, bdi ngudn nude ngay cing cd nhung bilu hien suy giam trong khi dan sd tang nhanh, nhu ciu su dyng nude cho phat trien ndng nghiep, cdng nghiep, thiiy dien... ngay cang cao. Cd mot thuc tS la, cac dy an thuy dien, thuy Igi diu chan ddng vao mua khd, dl lam cho vimg h? luu bj thieu nude. Diln hinh la nha may thuy dien Huang Diln (tai Huang Vin, Huang Tra) ngan ddng tii ngay 27/12/2009, do tich nude sdm tiong thang 12 nen d h? du da xay ra tinh trang thieu nude nghiem trpng, anh hudng den san xuit ndng nghi8p cho ha lim sdng Bd.
2.5. Xam nhSp mikn
Dd man trong cac sdng va tinh hinh xim nhip man vao cac ciia sdng d Thiia Thien Hui dao dpng tiiy theo miia khi hau, tinh hinh ddng md cua biln, vi tri xa gin ciia sdng va cua biln, dp sau dim pha cung nhu chu ki hilu. Dd man Idn nhit vao miia khd, d nai gin cua biln va thip nhit khi miia lii, noi cira sdng dd vao dim pha. Dp man vao miia khd d phi Tam Giang 10- 29%o, dim Thuy Tu 20-32%o, dim Ciu Hai 20-33%o, dim An Cu 30-35%o. NhChig nSm ban ban nang, man lin siu vl phia thugng luu ciia sdng (d Van Nien ti-en sdng Huong, gan ciu An L 6 tren sdng Bd va d Van Trinh tren sdng 6 Lau).
Dd man binh quin vimg cua sdng Huong tr8n 20%o, dp man Idn nhit xuit hien tir thing 6 den thing 8 tien 33%o. Trong 1 tiling cd 2 thdi ky man tuong ung vdi 2 thdi ky trilu, vao nhiing ngay diu thing va giGa thang im lich (dp min do dugc khoang 20,5%o).
Trong ngay, do vimg cira sdng Huang thiiy trilu thugc ban nhat trilu khong diu nen mdi ngay cd 2 ky nude len va 2 ky nude rdng, do dd man xuit hien 1 din 2 gid sau dinh trieu va 2 den 3 gid sau chan trilu.
Tir nam 2006, dip ngan m|n Thao Long tren sdng Huang duac dua vao sir dung d i giai quyet dugc tinh ti^ng nhiem man tien song, cdn lai cac con sdng tien dia ban diu d tiong tinh trgng nhiSm min thudng xuyen.
NGHIEN CUU CAC TAI BIEN THIEN NHIEN 0 DAI DONG BANG VEN BIEN TT HUE
2.6. Nvdc dang
Nude dang la hi?n tugng muc nude biln dang cao hon muc nude tiung binh do he qua nhiet dp Trai dit gia tang va khi cd bao anh hudng. CS khu vuc Thira Thien Hui, nude ding da quan sat trong can bio CECIL 1985 d Thuan An 1,9m, d Lang Cd 1,7m. Nude ding kit hprp trilu cudng lam muc nude biln cao 3-4m, han vao dit hin 2-3kni. Theo tinh toin, tiong chu ky khoang 100 nam cd kha nang xay ra nude dang d khu vuc ven bien Thira Thien Hu8 vdi dp cao 2,0m. Hien tugng nude dang se giy tic dpng tieu cue ddi vdi cac cimg dit tiiip ddng bing ven biln Thira Thien Hui cd dp cao tir 3,5-4m trd xudng do hien tugng bien lin, xdi Id, nhilm man va ngip lut tang cudng.
3. CAC NHAN TO TAC D Q N G GAY TAI BIEN THEN NHIEN CJ DAI DONG B A N G VEN BIEN THU^A THIEN HUE
3.1. Bia chit, dia hinh, dia mao - Dia chat:
O viing riiii, Idp vd phong hda ferosiaUt cd be day mdng, it thim nude, vimg ha luu cac be m^t ddng bing tich ty sdng, sdng - bien, bien dugc cau tao chu ylu bdi set bdt cd bl day mdng, kha nang thim nude yeu lam tang ty le nude chay tian tien mat din din su gia ting tinh chit nghiem tiong cua Iii lut.
Doan song chay qua viing ddng bang vdi dia hinh tuong ddi bang phang, bd sdng ciu tao chii yeu tCr dit cat, bdt, set mIm yeu, nguy co xdi Id bd sdng rit Idn.
Bd bien Thira Thien Hue ciu tao tir cac trim tich bd rdi cd dp gin kit kem, khdng chdng da dugc tic dpng ciia sdng vd true tilp vdi ip luc ddng chiy Idn. Diy chinh la mgt trong nhiing yeu to gdp phin gay xdi Id bd bien tinh Thira Thien Hui.
- Dja hinh:
Phia Tiy, Tiy Nam va Nam lanh thd li vimg niii vdi do cao dao ddng tir 750 din 1.800m. V8 mua ddng, tic dyng chin gid miia Ddng Bac ciia cic dSy niii giy ra mua Idn vdi cac tam mua Idn d A Ludi, Bach Ma. Mat khac, cac day nui cao giy ra hieu ung phan la nguyen nhan cua thdi tiet Idid ndng va Iian han tiong miia h&.
Viing ddng bing ven bien vdi dia hinh thap trung, cd he thdng dim pha Tam Giang - c i u Hai an ng& d phia ddng. Day Ii nguyen nhin lam giam khi ning thoat lu mdi khi cd lii Idn gay nen hien tugng ling lyt keo dai va ngap siu ciia khu vuc ddng bang thip.
Cac dai cat, cdn cat, dyn cat do gid cao 5-20m keo dai dpc theo bd bien vdi bl rdng 300 - 800 m da tid thanh nhfing de chin tu nhien giy bdi ling, xdi Id, bdi lip cira sdng, bd bien, phi hoai de dieu, tac dpng nghiem trpng den kha nang tieu thoat lii ra biln, lam trim tipng them tic ha,i cua lii lut.
3.2. Nhan td khi tuong, khi hau - Mua:
Suphan hda lucmg mua theo thai gian: Thira Thien Hui chii ylu mua vao miia Thu Ddng. Miia mua diln ra ti-ong 4 tiling (tir thing 9 din tiling 12) chiem 74,4% lugng mua nam. Ngugc lai, ti-ong mua it mua (keo dai tiong 8 thing), lugng mua chi chilm 25,6% lugng mua nam, lugng nude bdc hoi Idu, gay nen hien tupng ban han va xam nhip man.
Biln trinh ciia lugng mua nam d tinh Thira Thien Hui ndi chung va dii ddng bing ven biln ndi rieng cd hai cue dai. Mot cue dai vao tiling 5, 6 cd thi gay lu tilu man. Cue dai thu hai tir thing 8 din thing 12 hoac thing I, gay ra mot miia lii chinh.
Thing mua Idn nhat tiong nam la thing 10, tdng lupng mua thing dao ddng trong khoing tir 600 mm din tren 1000 mm. Su tip trung ciia lugng mua ciing nhu sd ngiy mua Idn lam cho khi nang xay ra \u lyt, xdi Id bd sdng tiong cac thing niy rit cao.
5d'ngay miffl.-Hing nam cd khoing 150-170 ngay mua d ddng bing ven bien. Vao mua mua, mSi thing cd 16-24 ngay mua. Nhiing dot mua keo dai nhieu ngay (4-6 ngay) tien diSn rpng thudng gay lii lyt, xdi Id bd sdng nghiem trpng. Ngugc lai, trong miia it mua chi cd 8 din 15 ngiy mua/thang. Nhihig dgt khdng mua keo dai lien tuc tir 6-7 ngay d6n 19-31 ngay, gay han hin va xim nhap man [2], [5].
Cudng do mua: Theo sd lieu quan tiic, lupng mua Idn lihit ngay tai Hue cd thi len tdi 500 den 900 mm. CJ Thira Thien Hue da timg xay ra nhiing tran mua vdi cudng dg rat Idn va di kem vdi nd la cic tai bien thien nhien tiong dd cd lii lyt, xdi Id bd sdng.
- Nhiet dg khdng khi: Ve miia ddng, nhiet dp trung biiih thing lanh nhit la 20 C. Trong mua he, vao cac thing ndng nhat (thing 6 va thing 7), nhiet dp trung binh cd the len den 28-29°C [3], khi cd gid miia Tiy Nam kho ndng, nhiet dp cao nhat cd the len tdi 40''C, thdi dilm nay thudng xay ra ban hin v i xim nhap man.
- DQ dm tuong doi cua khdng khi, lugng nude bdc hoi, chi so khd han:
Khi hau Thira Thien Hue rat khac nghiet va khic biet nhau giiia cac vimg, cac mua. Vao thdi gian bdc hcri Idn (thing 5-8 lugng nude bdc hai len tdi 87-150niro/thang), dp im tiong khdng khi thap (tir thing 4 den 8 - trimg vdi thdi ky hoat ddng gid mita Tay Nam khd ndng, dp am tuong ddi khdng khi ha thip din 73-79%), mua it, nhiet dd cao thudng xay ra han hin va xam nhap m^n d dong bing ven biln [4].
- Cdc hien tuang thai tiet dgc biet:
Thira Thien Hue Ii mpt tiong nhiing khu vuc cd lugng mua tiling binh nam Idn nhit ca nude. Mua Idn d day thudng do cac hinh thi thdi tilt nhu bao, ap thip nhidt ddi, dii hdi tu nhiet ddi, khdng khi lanh gay ra. Cac hinh till tiidi tilt nay khi cd su kit hgp vdi nhau s€ giy ra mua dac biet Idn.
NGHIEN CUU CAC TAI BIEN THIEN NHIEN 0 DAI DONG BANG VEN BIEN TT HL'E
3.3. Che dd thny van, hai van - Nhan td thuy van + Hinh thdi song ngoi:
Thira Thien Hue la mpt tiong nhiing khu vuc cd mat dp sdng sudi cao. Do dd, tin suat ngip lut d khu vuc nay rit Idn.
Da sd cic he thdng sdng tren dia ban tinh Thira Thien Hui cd chilu dai ngin, long sdng ddc va luu vyc hep. Dai bp phan sdng sudi chinh bat ngudn tii vimg niii cao, d thugng ngudn long sdng sau hinh chiJ V vdi cic vich niii ddc dirng; d ddng bang ddng sdng udn khiic, cd sy ddi hudng lien tuc va do vao phi Tam Giang - Ciu Hai trudc khi chay ra bi6n.
Nhiing die tnmg hinh thii kit hop vdi dia hinh luu vuc cic sdng da hinh thanh mot che dp thuy van phiic tap gay lii Idn vao miia mua va thieu nude tiong mua it mua.
-I- Che do thiiy van:
Lugng ddng chay, die biet la ddng chiy lu cung tang rat cao. Modun ddng chay nam va ddng chiy lij d day Idn nhit lanh thd nuoc ta.
He sd dieu tiet ty nhien (qj) (quan h6 giiia nude mat va nude ngim) ciia luu vuc sdng tien dia ban tinh Thira Thien Hue dao ddng tir 0,35-0,45 thugc loai kem, diy l i mpt tiong nhihig ylu td tic ddng sitih lu va nguy ca xiy ra lii Idn d khu vyc nay rit cao.
Su ddng md ciia bien khdng theo quy luat cu the ma chii ylu phy thudc dgng luc ddng chiy cua sdng vao cac mua bao lu. Do dd, da anh hudng khdng nhd tdi viee tieu thoat lu ciia sdng, ddng thdi lam bien dpng Idng din gay nen hien tugng xdi Id bd sdng.
- Nhan to hdi van:
+ Sdng: C) vimg bd bien Thira Thien Hue, khi cd bao, gid miia Ddng Bac tic dpng manh cd the phit smh sdng Idn cao tdi 4 - 5 m, thim chi Idn han; sdng cao, tic dpng gin nhu vudng gdc vdi bd bien gay ra hien tugng xdi Id.
-f Chi do thuy trieu: vung bien ven bd chi keo dai xip xi 127km nhung che dp thiiy trieu bien ddi khi phiic tap. Tir Di6n Huang den cira Thuin An, thiiy trieu thupc chi dp ban nhat trieu khdng diu vdi bin het sd ngay tiong thing la bin nhat trieu.
Chi dp thuy trieu cd anh hudng den tai bien xdi Id bd bien, muc nude bien dang va xim nhap min.
3.4. Ldp phu tho nhirdng
Nam nhdm dit chu ylu d ddng bang ven bien Thira Thien Hue la dit cdn cit v i dit cat biln, dat man, dit phen, dat phii sa, dit liy va than bim. Trir loai dit cat, cic Ioai dit khic d vung ddng bing cd khi nang trff nude tir kha den Idn.
Do viec sir dyng dat khdng hgp ly, viec phi rimg dau ngudn din den viec hinh thanh cac dai dit bac mau, kem dinh dudng, khdng cd kha nang tham giii nude d vung ddi niii
phia tiy ddng bing. Nude mua ty do chay vl vimg ddng bing, don li lai ven chin cic cdn cit d phia ddng, tao lu lyt cue bd.
Tren ddng bing ton tai cac hd uung, dim phi, dac biet cac cdn eat ven bien tid tiianh nhung gd de ty nhien ngin dudng thoit lii ciia ddng bing. Them viec cit bdi lap ciia sdng lam cho nude lu khd thoit dugc ra bien.
3.5. Ldp phii thirc vat
Riing ty nhien bi tan phi tiong chiln ti^nh vi khai thic bCra bai sau nay. DiSn tich rimg giam di nhanh chdng, rimg giiu giam 5951 ha ma chu yeu la d vanh dai nhiet ddi (d dd cao dudi 800m), dien tich rimg trung binh va rung ngheo cung bi suy giam nghiem tipng. Trong 4 nim 2006-2009, di^n tich rimg bi chiy binh quin 33,4 ha/nam. Nim 2009, cd 14 vy chay rimg, dien tich rimg bi thiet hai 15,5 ha. Viec suy giam nghiem tipng lap phu rimg la mpt tic nhin quan trpng lim giim kha ning diSu tiet nude va khien nguy eo cic tai bien thien nhien xay ra ngay cing tiim tipng ban.
3.6. Cac hoat dong nhan sinh
Cic hogt dpng ciia con ngudi nhu xay dyng cac cdng trinh dieu tiet, su dung nude tien sdng; khai thac rimg bira bii; sii dung dit khdng hpp ly nhu khai thic dat ddc vio muc dich lim nuong, riy, sy bung nd ve nha d, dit d, dat xiy dung hien xam pham vao ci vimg canh tac liia nude, vimg dat cd chiic nang chgm lu; viec ngan bd nudi trdng thuy sin lam thu hep Idng dan, cira thoat lii, vi pham vao hinh lang thoit lii, khiu dp ciu, cdng tien tuyIn giao thdng... da tic dpng true tilp din sy gia ting cua thien tai lu lyt, xdi Id bd sdng... Viec xiy dyng he thdng dutmg x i giao thdng, dac biet la qudc 10 s6,1 va tuyen dudng sit Bic - Nam, thuc sy dang la nhiing vat cin Idn cho viee thoit lii vi giy ngip lyt nghiem trpng d viing ddng bang.
4. CAC GL\I PHAP N H A M HAN CHE TAC HAI CUA CAC TAI BIEN THIEN NHIEN CJ DAI D 6 N G BANG VEN BIEN THlTA THIEN HUE
4.1. Cac giai phip cong trinh
* Cdc giai phap cdng trinh phong tranh, giam thieu thiet hgi do tai biin lu lyt gay ra:
Cin day nhanh tien dp xiy dyng cac hd chtia, dip thugng ngudn da myc tieu.
Cling cd va duy tii h6 thdng de dieu, kien e6 hda kenh muong dim bao dap ling phdng lu vdi tin suat 10%.
Tao hinh lang thoit lu an toin bing each nin thing khiic sdng cong, xac dinh hanh lang dn dinh tien sdng, tao cic cdng va khiu dd tieu thoat.
Ning cap h? ling ky tiiuat tai cic vung tipng ylu, phat triln, xiy dyng cong tiinh edng cpng va nha d kien cd dl vugt lii.
Cin cd cic giii phap chdng bdi lip cua sdng, nao vet Idng dan, khai ddng cac kenh, hdi, ting cudng kha nang tiioat lu, kit hgp giao tiidng thiiy.
NGHIEN cUu CAC TAI BIEN THIEN NHIEN 0 DAI DONG BANG VEN BIEN TT HUE
Trdng va bao ve riing dau ngudn de giam thip cuimg dp lu lyt, tiong cay chan sdng khu vuc cita sdng, ven bien.
* Cdc giai phap cdng trinh phong tranh thien tai xdi la bd sdng
Tai mpt sd khu vuc dang cd nguy ca xdi Id cao, can khin trucmg xiy dyng cic cdng trinh ke bd: Tiln hanh nao vet d Cu Chinh - Thuy Xuin - TP Hui, xay ke lit mii d bd trii sdng Huang (tai Xudc Du - Huang Hd - Huang Tra, Long Hd Ha - Huang Hd - Huong Tri, gin Chua Lmh My, Dia Linh - Huang Vinh - Huong Tra, Thanh Phudc - Huang Phong - Huang Tra, Thuan Hda A - Huang Phong - Hucmg Tra), d bd phii sdng Hucmg (tai Phutmg Kim Long - TP Hui, Tien Ndn - Phii Mau - Phii Vang), d hai bd sdng Huang (Vy Da - TP Hue), d bd trii sdng Bd (Lieu Cdc Ha - Quing Thp, Duang Son - Quing Thp), d bd phii sdng Bd (Thanh Xuan - Huong Viet).
* Cdc giai phap cdng trinh phdng tranh thien tai xdi la bd bien
Ddi vdi doan bd tir Hii Duang (Huang Tra) den ciia Hoan Duan (Phii Vang) vdi chilu dai doan bd cin bao ve vao khoang 5,2km, can xay dung khoang 26 ke md hin hinh chii T.
Ddi vdi Cira Thuan An, de dn dinh, thdng ludng \ a thoat lii, cin cd cac giai phip: Phia tiong cua sdng can xay ke ip mai bao ve bd cua dn dinh theo tuyen ludng da hinh thanh sau lii cudi nam 1999. Phia ngoai ciia sdng can xay dung 2 md hin song song vdi tuyen ludng nhim ngan eat van chuyfen tir phia Tay Bic v i Ddng Nam vin chuyen vio bdi lap ludng.
Doan bd tir ciia Thuan An den Hda Duan cd the ip dung bien phip nudi bii nhin tao de chdng xdi Id, tiic li bd sung cit vao vung bd dang bi xdi Id.
* Cdc giai phap cdng trinh phdng tranh han han, xam nhap man. mi/c nu&c bien ddng Cin diy nhanh tien do xay dung cic hd chiia, dip thugng ngudn da myc tieu. Cac hd chua ben canh nhiem vu chdng lu cho vimg ha du, cdn cd vai trd dim bao ngudn nude cho sinh hoat va sin xuit vao mua khd, giim bdt thiet hai do tai bien ban hin, xam nhap man.
Viec dip de sdng, biln la mot bien phip cdng trinh phd biln tiong phdng tranh ban han, ngan man va hien tugng nude bi6n dang.
Cic dja phuang nhanh chdng tien hanh nao vet, khai thdng ddng chay, lap them dng dan nude cdng suit Idn, tai nude ve cic tram bam.
Duy tu bao dudng cac tram bam thuyen de cd ke hoach bam chuyen nude cho mpt sd vimg khi myc nude sdng xudng thap.
Van hinh tot cdng trinh Thio Long, Cua Lie.
4.2. Giai phap phi cdng trinh
Xay dyng ca sd dir heu thdng nhit vl tiiien tai d Thira Thien Hui.
Xay dyng mang ludi tiidng tm lien lac phdng, chdng va giam nhe tiiien tai ddng bp tir tinh den xa.
Xay dyng hoan chinh mang ludi quan tiic khi tugng, thuy van, hai van va cac hien tirpng ichi tirgng thiiy vin nguy hilm nhu: bao, lii, xdi Id bd sdng, xdi Id bd biln.
Quan ly, tang cudng chiic nang ciia ldp phu tiiyc vat nhim han chi ddng chay mat, tang ddng tham, ban chS tic hai ciia lu.
Tang cudng chiic nang dilu tilt ddng chay ciia ldp vd phong hda, tiid nhudng.
Ban hanh cac van ban phip ly lien quan din phdng, chdng v i giam nhe thien tai.
Qui hoach vi dilu chinh cic diem dinh cu, cac diem dan cu.
Duy tri tang trudng kinh tl cao va b6n viing.
Tang cudng diu tu xay dung kit ciu ha ting ca sd, nhit li d vimg ndng thdn.
D I phdng ngira tai biln lu lyt, xdi Id bd sdng, tiiudng xuyen kiem tia, dinh gii kha nang chua nude va miic dp an toan ciia he thdng hd da cd.
c i n tang cudng quan ly nha nude ddi vdi boat dpng khao sat, tham dd, khai thac, van chuyen vi kinh doanh cit, sdi tren dia ban tinh.
iTng dyng tien bd khoa hpc cdng nghe, ky thuat va su dyng vat lieu mdi vao phyc vy cdng tie phdng chdng va giam nhe thiSt hai do thien tai giy ra.
Tang cudng hgp tie qudc te va tiong nude tiong linh vyc phdng, chdng va giam nhe tiiien tai.
5. KET LUAN
Ddng bang ven bien Thira Thien Hue la nai hiing chiu nhieu tai bien thien nhien nhu lii lyt, xdi Id bd sdng, bd bien, han han, xam nhap man, myc nude bien dang. Dudi tic ddng ciia bien ddi khi hau toan cau, cac tai bien thien nhien dien ra vdi quy md, cudng dp va tin suat ngay cang Idn.
Cac nhin td tic ddng giy tai bien thien nhien d dai ddng bang ven biln Thira Thien Hui bao gdm: nhin td khi tugng, khi hau; dilu ki6n dia chat, dia hinh, dia mao; nhin td chi dp thuy van, hii van; ldp phu thd nhudng; ldp phu thuc v$t; cac hoat ddng nhan sinh.
Tir viee xic dinh dupc cac nguyen nhin chinh giy ra cac tai biln thien nhien d dii ddng bing ven bien Thira Thien Hue, de xuit cac giii phip thudc hai nhdm cdng trinh va phi cdng tiinh nhim giam thieu thiet hai do tai biln thien nhien giy ra vdi myc tieu lau dai la chu dpng phdng, tianh, thich nghi dl phat tiiln.
NGHIEN ctru CAC TAI BIEN THIEN NHIEN 0 DAI DONG BANG VEN BIEN TT HUE
TAI LIEU THAM KHAO
[1] Nguyin Van Cu, Ph?m Huy Tien (2003). Sat Id bd biin miin Trung Viet Nam. NXB Khoa hpc va KS thuat, Ha Noi.
[2] Dai KTTV khu vyc Trung Trung Bo (1998-2008). Dac diim KTTV moi trudng khu vuc Trung Trung Bg nam 1998. 1999, 2000, 2001. 2002, 2003. 2004. 2005. 2006.
2007, 2008. Da Ning.
[3] Sd KHCN & MT Thira Thien Hui (2004). Ddc diim khi hau thuy van Thira Thiin Hue. NXB Thuan Hda, Hui.
[4] Trung tam Du bao Khi tugng Thiiy van tinh Thira Thiea Hui (2001). Tap s6 lieu khi hau tinh Thiea Thien Hue. Hui.
[5] Uy ban nhan dan tinh Thira Thien Hui (2005). Dia chi Thira Then Hui - Phan Tjf nhien. NXB Khoa hpc Xa hoi. Ha Noi.
Title: A STUDY OF NATURAL CATASTROPHES IN RANGE OF THE COASTAL PLAIN IN THUA THIEN HUE PROVINCE
Abstract: The range of the coastal plain of Thua Thien Hue is very sensitive to natural disasters and impacts of climate change alike. Every year, Thua Thien Hue province generally and the range of the coastal plain in particular have to bear severe consequences caused by natural disasters. Especially in recent years, the natural catastrophes such as typhoons, floods, riverbank erosion, coastal erosion, drought, salinization, rising sea, etc... have occurred with a significantly increasing intensity and frequency, causing a great loss of residents' lives and property, harming the relics of the old capital which has been recognized as a UNESCO cultural heritage of humans, as well as having a bad influence on the ecological environment.
TS. NGUYEN THAM
Tnrcmg Dai hpc Su pham - D?i hoc Hue PHAN ANH HANG
Khoa Dia ly, Trudng Dai hpc dan lap Phii Xuan, Hue
