Tap chi KHOA HOC BHSP TPHCM ^^ ^' "«'" ^"'^
"I DANH GIA VAI TRO CUA CAC HINH THE THdl TiET GAY Ml/A LU d Liru Vl/C SONG HU'ONG, TINH THtTA THIEN HUE - GIAI BO^N 1976 - 2013
NGUYEN HOANG SON'
TOM TAT
Vai trd ciia cdc hinh thi thdi Hit gdy mua lu a luu vuc sdng Huang tinh Thira Thien Hiii dupe ddnh gid thdng qua phdn tich si lieu mua Idn dien rpng thai ki 1976 - 2013 vd 99 trdn lii trang thdi ki 1981 - 2013. Cd 8 loai hinh thi gdy Iii chii yiu vd 5 hinh thi khdng chii yiu (hoac dan thudn hoac kit hap) dd gdy ra cdc dpi mua sinh lu trong 33 ndm tren liru vuc song Hirang. trong do bao. dp thdp nhiet ddi, ddi hdi tu nhiet ddi va khong khi Ipnh dupe xem Id cdc nhdn td cd anh hudng rdt Idn.
Tir khda: hinh thS thai tik, mua, lu, luu vuc song Huong, tinh Thira Thien Hul ABSTRACT
Evaluating of weather complexions causing diluvial rains on the Huong river valley in Thua Thien Hue province -period 1976 - 2013
The role of the weather complexions causing diluvial rains on Huong river valley was estimated by data analysis of heavy rains on large area from 1976 to 2013 and 99 floods f-orn 1981 to 2013. There are eight official weather complexions and 5 unofficial ones bringing diluvial rains for 33 years on Huong river valley, in which great factors were typhoon, intertropical low pressure zone, intertropical convergence zone and winter monsoon.
Keywords: weather complexions, rain, flood, Huong river valley, Thua Thien Hue province.
1. Dat van de
Luu vuc song Huong la mot viing rong 1cm njm o vi tri trung tam va bao triim phan Ion lanh tho tinh Thiia Thien H u l Day la mot vimg tap trung nhieu tikm lire kinh te eiia tinh, voi 68% dien tich tu nhien, 67,6% dan s6 nhung dong gop 75 - 85% gia tri GDP, gan 90% gia tri gia tang cong nghiep va 80 - 85% gia tri xuit khau... Viing thuong lim va vimg trung lim co nhiSu tiSra nang Ion vS phat triSn cac nganh nong nghiep nhu trong cay cong nghiep, cay an qua, chan nuoi gia siic, tr6ng rimg va kinh ti viron doi. Vimg ha luu n6i voi cac dim pha ven biSn co thS phat triln danh bat va nuoi trong thuy hai san. Vimg trung luu co thanh ph6 HuS la trung tam van hoa, du Heh cua tinh va ciia ca nude, dac biet c6 do Hui dugc UNESCO xip hang la di san van hoa thi gioi. Vanh dai phu can co kha nang phat triSn nhieu nganh cong nghiep quan trong, phat trien du lich va cac nganh dich vu khac. Luu vuc song Huong nim trong khoang toa do dia li tit 107°09' din 107»51' kinh do Dong va 15»59' din 16° 36 ' vl do Bic, trong vanh dai nhiet doi bic ban ciu va la khu vuc chiu anh huong gio miia chau A.
Nam o phan trung do cua dit nude, viing luu vuc song Huong, tinh Thira Thien Hul
TS, Tru'ong Bai hpc Su pham, 0?i hpc Hu<
Tap chi KHOA HOC DHSP TPHCM Nguyen Hoang San
vita chiu anh huong cua gio miia dong bac vira bi gio miia tay nam chi ph6i. Do vay, day la noi luan phien chiu tac dong va tranh gianh anh huong ciia cac khdi khong khi CO nguon goc khac nhau theo miia. Chinh su hoi tu eua khong khi lanh tir phia bic tran xuong va khong khi nong am tit phia nam di chuyen len da tao ra cac hinh thS thcri tiSt gay mua va hinh thanh nhimg tran lu Ion va lu quel lam truot lo dit, xoi Id bo song...
Bai viet nham danh gia vai tro cua eac hinh thS thai tiSt gay mua sinh ra lu lut o luu vuc song Huong de lam ca so cho viec du bao mire do ngap lut, phuc vu quy hoach va phat trien kinh te - xa hoi dja phuong.
2. Cff sff tai lieu va phvomg phap nghien ciru 2.1. Casd tdi lieu
Viec danh gia vai tro cua eac hinh thS thoi tiet gay mua lii 6 luu vuc song Huong duoc dua tren s6 lieu quan trie tir cae tram quan trie khi tuong, thuy van va cac t6 chire, don vi nghien cim tren dia ban luu vuc song Huong bao g6m:
Tai lieu khi tuong: Trong luu vuc va viing phu can co tong s6 10 tram do mua, trong do CO 3 tram do cac yeu to khi tugng do la: Hul, Nam Dong va A Luoi.
Tai lieu thuy van: Tren luu vuc co 8 tram do thuy van trong do c6 5 tram do muc nuac, luu lugng, con lai la do muc nuac. Tinh den nam 2013 tren liru vuc chi con lai 1 tram thiiy van cap 1 do Bg Tai nguyen va Moi trucmg quan li, do la tram Thuong Nhat tren song Ta Trach.
Luoi tram quan trac khi tugng thiiy van luu vuc song Huong dugc trinh bay cr bang sau:
Bang 1. Luoi tram khi tuang thdy van luu vuc sdng Huong vd vimg phu can TT
1 2 3 4 5 6 7 8 9 10 11 12
Ten trgim Hue (Phu Bai) Nam Dong A Luoi Kim long PhuOc Phii Lgc Thuong Nhat Duong Hoa Binh Dien
C6Bi Truoi CaCut
Song
Huong Bo Ta Trach Ta Trach Hihi Trach B6 Truoi Vung Tay
Yeu to do T,U,V,Z,X,N T,U,V,Z,X,N X,T,V,Z
H,X H,X X H,Q,X
H,Q X H,Q
X H,Q H,Q,X
H
ThM ki quan trac 1901-2008 1973-2008 1976-2008 1977-2008 1976-2008 1978-1988 1979-2008 1986-1987 1977-1985, 1992-
2008 1979-1985 1979-2008 1977-1985 1993-1996 1978-1982
Ghi chii Dang boat dong Dang hoat dong Dang hoat dpng Dang hoat dpng Dang boat dpng Dang hoat dpng Dang hoat dpng Dang hoat dong
Ghi chii cdc ki hieu: Dang hoat dpng (din 2013); T - Nhiet dp khong khi (°C); U - do im khong khi (%); V - t6c dp gio (m/s); Z - boc hoi (mm); X - mua (mm); N - nSng (gicr); H - muc nuijc (cm); Q - luu lugng nude (m'/s)
Tap chi KHOA HQC DHSP TPHCM Sd 61 nam 2014
.Ben canh s6 lieu tir eac tram khi tugng, thuy van tren luu vuc, bai viet con ke thira s6 lieu tit Dai khi tugng thiiy van khu vuc Trung Trung bo va cac cong trinh nghien ciru cua don vi va ca nhan da to chue dieu tra tren dia ban.
2.2. Phuang phdp nghien ciru
Cac phuang phap chinh dugc sir dung trong viec danh gia vai tro ciia cac hinh the thai tiet gay mua lii 6 luu vuc song Huang bao gom:
Phan tich, thSng ke khi hau: Phan tich diln bien cac dgt mua Idn bing s6 lieu mua mat dit, xac dinh pham vi khong gian anh hudng ma cae dot mua Idn gay nen.
Phuang phap khi tugng synop: Phan tich ban d6 synop ve cac hinh the thdi tiet vi td hgp cac hinh thS thdi tilt gay mua, phan loai thing ke tin suat hoat dong cua eac loai hinh thi thai tilt va td hgp cac hinh the thdi tilt gay mua Idn.
Phuang phap phan tich dia 1! tdng hgp: Phan loai dja li - hinh thai dia hinh cac khu vuc vdi nhtrng hudng sudn, thi niii tilm nang tuong tac vdi co chi gSy mua tren toan lim vuc sdng Huong.
Ngoai cae phuong phap chinh neu tren, trong qua trinh nghien cim chiing toi con phdi hgp sir dung cae phuong phap chuyen nganh truyen thdng khac nhu: Phuong phap khao sat thuc dia, phuang phap ke thira phan tich va diic ket cae ket qua eiia cac cong trinh nghien cim lien quan, phucmg phap chuyen gia... de cac nghien cim cd duge kit qua tdt nhat.
3. Ket qua nghien ciin va thao luan
3.1. Phdn tich dac diem mua Idn vd vai tro cda nd dii vdi viec hinh thanh lit tren luu vuc sdng Huong, tinh Thira Thien Hui
Mot dgt mua Idn la dgt mua ma nguyen nhan gay ra nd cd tinh he thing, bao hTJm it nhat 2/3 lanh thd, cd lugng mua ngay > 50mm va toan dgt > 100mm [8], Vdi dinh nghia nay d tren luu vuc sdng Huong tir 1976 - 2013 da thing ke dugc 214 dgt mua Icm tren dien rdng (hinh 1). Dgt mua Idn xuit hien diu tien vao thang V, VI gpi la mua tilu man, sau dd giam dot nggt trong thang VII, tang din trong thang IX, dat cue dai vao thang X, XI va keo dai din thang XII.
So d o t iTiij-a
40
0 V
^ • S 6 . J 9 t m u - a [ 4
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5 2 3
VII 1 0.5
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VIII 11 5 1
• i /
M
IX 36 1 6 8
i • 74 X
34 6 Tin
•'
• N •
"•-
XI 65 30 4
suk\ (%)
S
^^
XII 18 8 4
40.0 35.0 30.0 25 0 20 0 150 10.0
Hinh 1. Cdc dm mua Ian vd tdn sudt xudt hien mua Ian dien rong theo cdc thdng tren liru vuc song Huang tinh Thira Thien Hui (tie 1976 - 2013)
Tap chi KHOA HOC BHSP TPHCM Nguyen Hoang San
Cae dgt mua Icjn chii yeu tap trung vao thdi ki tir thang IX den thang XII, dac biet la thang X va XL Vao thdi ki nay trung binh hang thang cd 2 - 3 dgt mua 1cm dien rpng.
Nhin chung mua nhieu va mua to thupc phan luu vuc phia Tay va phia Nam, nhiing noi cd dia hinh dugc nang dan len bdi cac khdi niii Trucmg Son d phia Tay va eac khoi nui chay ngang nhd ra biin d phia Nam. Nam 1985, 1995, 1996, 1998, 2001, 2005, 2007 va 2011 la nhihig nam cd sd dgt mua Idn dien rdng nhieu nhat (8 - 10 dgt) [2], [6].
Nam 1976, 1977, 1982, 1991 va 2012 la nhthig nam sd dgt mua Idn dien rdng cd tn sd nhd nhit (2 - 3 dgt). Tuy nhien, sd lugng eac dgt mua liSn dien rdng khdng quyet dinh hoan toan viec hinh thanh va cudng dp ciia lu trong khu vuc. Vi du nam 1999 la nam cd tran lii lich sir tren luu vuc sdng Hucmg, gay rat nhieu thiet hai ve ngudi va tai san nhung sd dgt mua Itm khdng nhieu (4 dgt) [1]. De danh gia vai trd eua mua Idn ddi vdi su hinh thanh lii t^i luu vuc sdng Huong, ngoai sd lugng cac dgt mua lim can phai quan tam den cac dae trung ve cucmg dp mua. Mot trong cac dac trung dd la sd ngay ed mua Idn (> 50mm/ngay) va sd ngay cd mua rat lein (> lOOmm/ngay). Tap hgp cae sd lieu thong ke ve sd tran lu xay ra trong timg nam, so sanh vdi sd ngay mua Idn va mua rit idn d liru vuc sdng Huong chung ta thay rat ro mdi tucmg quan chat che giira chiing.
Trung binh hang nam tren luu vuc sdng Huong xay ra 5 - 6 tran lii cd bien dp > Im. LG tap trung nhiiu vao thang X va thang XI, triing vdi thdi gian cd sd ngay mua Idn va mua rit Icm nhiiu nhit. Vao thdi gian nay hang thang trung binh ed 2 - 3 trjn lii, ung vdi sd ngay ed mua Idn va rit Idn la 4 - 5 ngay/thang [2], [3], [4], Lugng mua ngay cue dai trong thdi gian nay len tdi 300 - 400mm/ngay, tiie la thude loai mua rit liin. Diiu nay chung td mdi lien quan chat che giua mua va lu. Do dd, viec nghien ciiu, du bao mua Itjn rit hiru ich ddi vdi viec du bao cung nhu phdng tranh cac tran lu lein tren cac luu vuc sdng.
3.2. Nghien ciru dgc diim /«lut 6 luu vuc sdng Huang tinh Thira Thien Hue
* Miia lii: Ciing vdi miia mua, mua lii d luu vuc sdng Hucmg keo dai tir thang X din thang XII hang nam [5], [7], [9], Tdng lugng ddng chay trong miia mua lu chiim 69,7% tdng lugng ddng chay trong nam. Ngoai lii chinh vu cdn xuat hien lu tilu man trong thang V, VI vdi tin suit xuit hien 2,5 nam/1 lin. Lu sdm xuit hien trong thang VIII, IX; lii muon xuit hien trong thang I.
* Sd tran lu: Hang nam cd 3 - 4 tran lu idn hon mire bao ddng II. Nam nhieu nhat cd 8 tran, nam it nhit cd 1 tran. Nhiing nam chiu anh hudng ciia LaNina thi sd dgt lu tang len ro ret, nhu nhiing nam: 1996 cd 7 dgt lu, 1998 cd 6 dgt lii, nam 2000 cd 6 d(;rt lu, nam 2007 cd 8 dgt lii.
* Thai gian keo ddi: Luu vuc sdng Huong ed do ddc lim vuc va long sdng Idn, tham thuc vat trong lim vuc lai hi tan pha nen kha nang tap trung nude nhanh, lu len nhanh va xudng nhanh, thdi gian lu keo dai khoang 3 - 5 ngay, dai nhit 6 - 7 ngay.
* Thai gian truyin lii: Tde do ddng chay lu kha Icjn, thdi gian truyin lu tir 5 - 12 gid vdi khoang each 51 km tit thugng luu din ha luu.
Tap chi KHOA HQC DHSP TPHCM sS 61 nam 2014
* Bien dp W: Bien do muc nude lu (chenh lech giita m\fc nude dinh lu vdi chan lu) ciia mot tran lu d luu vuc sdng Huong thudng tir 3 - 5m, phu thude vao lugng mua va cucmg suit mua tren luu vuc va hinh dang mat cat sdng.
* Cudng suit lii: Cudng suit lu (su biin ddi eua mvc nude trong mgt don vj thdi gian) cua cae tran lu d luu vuc sdng Huong kha Idn. 6 thugng luu tir 1 - 2m/h, d ha luu
tir0.5-lm/h. _ '
* Dinh lii: Dinh lu Idn nhit hang nam cd sir giao dgng rit Idn. Sv giao ddng eiia dinh lu hang nam cd lien he kha chat che vdi hien tugng ENSO (ENSO Id sifphoi hop hoat ddng giOa hai Men tuang xay ra d dai ducmg (El-Nino, La-Nina) vd a khi quyin (dao ddngNam Bdn Cdu - Southern Oscilation - viit tdt Id SO). Nhiing nim chju anh hudng cua El Nino nhu nam 1982, 1987, 1991, 1994, 1997 va 2012 cd dinh lii thip [1];
cdn nhiing nam chju anh hudng ciia LaNina cd dinh lu vugt trdi cac nam khac nhu nam 1995, 1998 va 1999.
Neu phan muc nude dinh lii tai Kim Long tren sdng Hucmg theo cac chi tieu:
dudi 3m la lii nhd; tir 3 - 4 m la lu vira va tren 4m la lii lein thi trong 37 nam (1977 - 2013) ta cd ket qua sau:
Bang 2. Phdn loai lU Idn nhdt trong ndm tren sdng Huang theo cdp muc nude lU (tir 1977 - 2013)
Myclu Lii nhd (< 3m) Lu vira (3 - 4m) Lii Lein (> 4m)
Tong
So nam 9 15 13 37
Tan suat (%) 24,3 40,5 35,1 100
Kit qua cho thiy frong 37 nam thi cd 13 nam lu Idn (35,1%), 15 nam Hi vira (40,5%) va 9 nam lu nhd.
Sd lieu quan trie hang nam cung cho thiy, su biin ddi mirc nude dinh lii cao nhit dien ra theo mdt chu ki nhit djnh: khoang 4 - 6 nam cd lii vira va nhd thi cd 2 nam lu Idn lien tiip nhu: 1983 - 1984; 1988 - 1989; 1995 - 1996; 1998 - 1999. Mdt sd tran lu tieu bieu cd dinh lii cao nhit d sdng Huang tai Kim Long nhu sau: 1953: 5,48m; 1975:
4,72m; 1983: 4,88m; 1990: 4,56m; 1995: 4,65m; 1996: 4,55m; 1999: 5,81m.
*Luu lupng lii: Muc nude biin doi eua ddng chay sdng Huong rit Idn, luu lugng eve dai Idn gap 10 - 30 lin luu lugng trung binh nhiiu nam. Theo tinh toan thi luu lugng lu tai Kim Long thang XI/I999 la 14.000 m'/s; thang IX/1953 la 12.500 m'/s.
Tong lugng nude tren toan bg cae sdng dd vao viing ddng bang Thira Thien Hui tir ngay 1 - 6/XI/1999 la khoang 307 ti m'. Kit hgp vdi mua cue Idn tai chd lam 90% lanh tiid viing ddng bang ngeip tit 1 - 4m.
_ * La quit: Dja hinh luu vuc sdng Huong bj chia cit rit manh, niii cao, sdng sudi sau, eac mai doc Idn ket hgp vdi mua Ign nen dl gay ra lu quet. Theo kit qua diiu tra d
Tap chi KHOA HOC BHSP TPHCM Nguyen Hoang San
luu vuc sdng Huong da xay ra cac tran lii quet vao nam 1953, 1975, 1999 va 2007 vdi cac dang lu quet nghen ddng, lu quet sucm ddc, lu quet hdn hgp, lu bim da.
* Ngap lut.- Ngap lut xay ra khi lu sdng qua Idn, nude lu tran qua bd sdng cha>
vao cae vimg thap ven sdng lam cho mot viing rgng Idn d hai ben bd sdng ngap chii trong nude lu. Do luu vyc sdng Huang cd do ddc Icim, 'Song ngin, ddng bing thip trung, cira tieu thoat kem nen nude it lai rit nhanh. Cac tuyin dudng sit, dudng bd c5' ngang hudng chay tao nen nhimg ducmg ngan lu. Nude lu len vdi cudng suit rit lijn nhung nit eh|m do anh hudng cila thiiy trilu va cae ducmg ngan lii gay ngap lut rit sau d viing ddng bing hep va khu ddng dSn cu.
3.3. Phdn tich cdc hinh thi thdi tiit gay mita la & lieu vuc sing Huang tinh Thira Thien Hue
Dua vao cac tai lieu mua tit 1976 - 2013, cac tran l i tren sdng Huong tit 1981 - 2013 ciia Trung tam Du bao khi tugng fliuy van tinh Thiia Thien Hue va Dai khi tugng thuy van khu vuc Trung Trung Bg chiing tdi budc diu nhan dinh vl cac hinh thi thdi tilt gay mua sinh lii tren lim vuc sdng Huong tinh Thira Thien Hui (bang 3).
Bang 3. Cdc hinh the thdi tiet gdy mua lad lini vuc sdng Hucmg tinh Thira Thien Hui (1981 - 2013)
STT 1 2 3 4 5 ' 6
7 8 9
Lo^i A B C D E F G H 1 Tong
Hinh the thdi tilt Khong khi lanh
Bao hoac ap thap nhiet ddi anh hudng true tiip Khdng khi lanh ket hgp vdi hoi tu nhi?t ddi Khdng ,khi lanh ket hgp vdi ddi gid ddng tren cao Khdng khi lanh ket hgp vcH bao hogc ap thap nhiet ddi
Khdng khi lanh ket hgp vdi hpi tu nhiet ddi va Ain gid ddng tren cao
Khdng khi lanh ket hgp ven ap thip nhiet ddi hoac bao, hpi tu nhiet dtji va ddi gid ddng tren cao Hpi tu nhiet ddi ket hgp vdi ap thap nhiet ddi Cac hinh the khac
So tran lu 4 20
7 14 23 6 9 5 11 99
Tan suit (%) 4 20,2
7.1 14,1 23,2 6,1 9,1 5,1 11,1 100 Qua bang 3 cho thay trong tdng sd 99 tran lii da thdng ke thi loai hinh the E (khong khi lanh kit hgp vdi bao hoac ap thip nhiet ddi) 14 hinh thi gay mua sinh lii nhiiu nhit, sau dd la hiiih thi B (bao hoac ap thip nhiet &n anh hudng tr\tc tiip). Sy phan bd theo thdi gian cua cae tran lii do cac hinh thi thdi tilt tren gay ra dugc trinh bay d hinh 2:
Tap chi KHOA HOC BHSP TPHCM S6 61 nam 2014
Sot 50 45 40 35 30 25 -
^ ^ S o t r ^ n l u
—•—Tan suat (%}
an iri
V 1 1 0
VI 1 1.0
VII 0 0.0
- 4 _^
VIII 4 4.0
y
/ /
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IX 12 1 2 1
• s ^
M m • • •
X 46 46.5
Tiin.sujit Co)
V
J L X
I K • ^ •
XI 30 30.3
K,
s.
XII 5 5.1
5O0 45.0 40.0 35.0 30.0 250 20,0 15.0 10.0 5.0 0.0
Hinh 2. Cdc trdn lu vd tan sudt xudt hien III theo cdc thdng tren sdng Huang tai Kim Long (1981-2013)
Qua hinh 2 chiing ta thiy ring cac hinh the thdi tilt gay mua sinh lii tren luu vuc sdng Huong bit diu xuit hien d thang V, VI (lii tieu man), thang VII mua khdng gay lii, bat dau tang len vao thang Vlll, IX (lii scim), cue d^i vao thang X, XI va ket thiic miia lii vao thang XII. Sau day se trinh bay cu the ve dac diem cua cac hinh the thdi tiet gay mua sinh lii tren luu vuc sdng Hucmg.
3.3.1. Khdng khi lanh (A)
Khdng khi lanh kem theo Front lanh anh hudng kit hgp vdi dia hinh. Dang hinh the nay xuit hien nhieu tren luu vuc sdng Hucmg nhung kha nang sinh lii thi chiim tin suat nhd (4%>). Khdng khi lanh gay mua lu thudng xuit hien vao thang XI va XII, 10 do hinh the nay gay ra la lii nhd hoac vira va la dang lii don.
3.3.2. Bdo hoac dp thdp nhiet ddi dnh hirdng true tiip (B)
Hinh the nay thudng xuat hien tir thang V din thang XI, tSp trung chu yiu vao thang IX va thang X (chiem 54%). Bao hoac ap thip nhiet ddi anh hudng tr^c tiip la hinh the gay mua sinh lu Idn (20,2%). Lu do hinh thi nay gay ra chu yiu la lii vira va lii Icm (chiim 61%), lu nhd chiim 38,4%. Lii liin tap trung chu yiu vao thang X va thang XI, lu nhd tap trung chu yiu vao thang VIII va thang IX.
3.3.3. Khdng khi lanh ket hap vdi hoi tu nhiet dai (C)
Loai hinh the nay chiim 7,1% tin suit xuit hien lu tren luu vuc sdng Huong. LO do hinh the nay gay ra thudng xuit hien vao thang IX, X va chu yiu la lu vita. Tuy nhien, cung cd nhiing nam lu do khdng khi lanh kit hgp vdi hdi tu nhiet ddi gay ra lii dac biet idn nhu tran lii thang X/1995. Khdng khi lanh kit hgp viii hgi'tu nhiet ddi tir ngay 6 - 9/X/1995 da gay mua rit Idn dien rdng tren luu vuc sdng Huang, dinh lu tji Kim Long dang cao 4,65m, lam gin 20 ngudi thiet mang, hon 1000 ha Ilia bi ngap ung, thiet hai ude tinh khoang 66 ti ddng.
40
Tap chi KHOA HOC DHSP TPHCM Nguyin Hoang Sam
3.3.4. Khong khi lanh ket hpp vdi dai gio ddng tren cao (D)
Hinh thi D thudng gay mua lii vao thang X va thang XI. Lii do hinh thi D gay ra tren luu vuc sdng Huong chiim 14,l%i so vdi cac hinh thi khac. Hinh thi nay thudng gay ra lu nhd va vira, trir trudng hgp chiu anh hudng ciia khdng khi lanh tang cucmg thi se sinh ra lu liin (nhu fran lii thang XI/2004).
3.3.5. Khdng khi lanh kit hap vdi bao hoac dp thdp nhiet ddi (E)
Day la hinh the xuit hien nhiiu nhat trong cac hinh the gay mua lii d luu vuc sdng Hucmg. Trong 99 tran lu dugc quan trac, hinh the nay gay ra 23 tran lu (chiem 23,2%) va chu yeu xuit hien vao thang X va thang XI. Hinh thi E chii yiu gay mua sinh lu vita va lu IcJn (chiim 73,7%), diln hinh nhu tran lu cac nam 1988, 1990 va nam 1998).
3.3.6. Khdng khi lanh kit hpp vol hdi tu nhiet ddi vd ddi gid ddng tren cao (F) Hinh thi F xuit hien va gay mua lu d luu vuc sdng Huong vao thang X. Loai hinh the n^y chiem 6,1% so vdi cae hinh the khac va cung cd the gay ra lu nhd, lii vira hoac lii Idn tiiy vao cudng dp tac ddng cua mdi hinh the rieng biet.
3.3:7. Khdng khi lanh kit hap vdi dp thdp nhiet ddi hoac bdo, hdi tu nhiet doi vd ddi gid ddng tren cao (G)
Tan suat loai nay chi chiem 9,1%, xuat hien trong khoang thdi gian tir thang X din thang XII. Khi hinh thi G xuit Men se gay ra mua rit Idn tren dien rdng v4 thucmg tao nen nhiing tran lii dac biet Idn, dien hinh la 2 tran lii vao eac nam 1983 va 1999.
3.3.8. Hoi tu nhiet ddi kit hop vdi dp thdp nhiet ddi (H)
Hdi tu nhiet ddi kit hgp vdi ap thap nhiet ddi chu yeu gay ra lu stjm vao thang VIII va thang IX, Lii .do hinh thi nay gay ra rit it, chi chiem 5,1% va thudng la lii nhd va lii vira.
3.3.9. Cdc hinh thi khde (1)
Cac hinh thi khac bao gdm 5 hinh thi phu: Ddi gid ddng tren cao; Khdng khi lanh kit hgp vdi bao hoac ap thip nhiet ddi va ddi gid ddng tren cao; Khdng khi lanh kit hgp vdi hdi tu nhiet ddi va ap thip nhiet ddi; Hoi tu nhiet ddi kit hgp vdi ddi gid ddng tren cao; Ap thap nhiet ddi kit hgp vdi ddi gid ddng tren cao.
Bay la cac hinh thi it xuit hien trong thdi gian 33 nam (tit 1981 - 2013). Cae hinh thi nay xuit hien trong khoang thdi gian tir thang IX din thang XII, tdng hgp cua 5 hinh thi gay mua nay cd 11 tran lu xuat hien, chiem la 11,1%.
4. Ket luan
Thdng qua viec sir dung chudi sd lifu mua va sd lieu ve muc nude lu tren sdng Huong cua Trung tam du bao khi tugng thuy van tinh Thira Thien Hue va Dai khi tugng thuy van khu vuc Trung Trung Bd, ta thiy trong 99 tran lii cua 33 nam (1981 - 2013) xay ra tren luu vuc sdng Hucmg ed 8 loai hinh the chil yeu va 5 hinh thi phu (hoSc don thuin hoac kit hgp) dugc xem la nguyen nhan chu yiu gay ra mua lii.
Cae hinh thi gay lii tap trung chu yeu vao thang X va thang XI, chiim 76,7% sd tran lu eua eac thang cdn lai.
Tap chi KHOA HOC BHSP TPHCM Sd 61 nam 2014
Vao thdi gian diu miia lu (thang Vlll, IX), nguyen nhan gay lu chu yeu la do s.
hoat ddng cua bao va ap thip nhiet ddi hoac hoi tu nhiet ddi ket hgp vdi ap thap nhiel ddi. Lugng mua ciia cae hinh thi nay tuang ddi lijn, thdng thudng khoang tren lOO mm/ngay. Tuy nhien, vao thdi gian nay kha nang diiu tilt eua sdng Huang cdn tdt nen cac tran lu chu yeu la lii nhd va lu vira.
Tit thang X din thang XII khdng khi lanh ddng vai tro tac nhan rat quan tronj trong viec kit hgp vdi cac hinh thi khac gay mua sinh la tren dien rdng d luu vuc song Huong. Theo sd li$u thdng ke khdng khi lanh cd anh hudng trong viec tao ra 63 fran li trong tdng sd 99 tran la eua 33 nam (1981 - 2013). Khdng khi lanh thudng ket hgp vfi cac nhiiu dpng thdi tilt khac nhu: bao, ap thip, hdi tu nhiet ddi, ddi gid ddng tren cao... D5c biet vao cudi thang XI diu thang XIL do cd su boat dgng tSng cudng ciia khdng khi lanh, cac tran mua dac biet Idn thudng xay ra vdi cudng do cao lam cho kha nang diiu tilt nude cua sdng trd nen kem va ngap lut tren lim vuc xay ra nghiem frong han.
c i n hit siic chii y din 2 loai hinh thi la: khdng khi lanh ket hgp vdi bao hojc ap fliip nhi$t ddi (E); bao hoac ap thip nhiet ddi anh hudng true tiip (B) vi hai hinh thi nay xay ra nhiiu nhit vdi lugng mua rit cao, cd thi gay nen tinh trang ngap lut dien rdng d luu vyc sdng Huong.
Mac dii chi chiim tin suit kha it (9,1%) nhung loai hinh the la Khdng khi lanh ket hgp vdi ap thap nhiet ddi hoac bao, hdi tu nhiet ddi va ddi gid ddng fren cao (G) lai cd the gay nen tinh frang mua la rat nghiem trpng bdi lugng mua phd bien ngay do dugc rat cao va thcri gian anh hudng ngap lut keo dai.
Ngoai 8 hinh thi chu yiu cdn ed cac hinh the khac dugc coi la khdng chu yiu gay mua sinh lu rit hilm khi xay ra tren luu vuc sdng Huong. Hinh thi khdng khi lanh kit hgp vdi bao (hoac ap thap nhiet ddi) va ddi gid ddng tren cao xay ra 3 lin trong 99 Ban lu cua 33 nam (1981 - 2013), eac hinh thi: ddi gid ddng tren cao; khdng khi lanh kit hgp vdi hdi tu va ap thap nhiet ddi; hdi tu nhiet ddi kit hgp vdi ddi gid ddng tren cao;
ap thap nhi$t ddi kit hgp vdi ddi gid ddng tren cao chi xay ra 2 lin trong 99 tran lu ciia 33 nam.
De di den mdt nhan dinh chinh xac hon vl vai trd ciia cac hinh thi thdi tilt gay mua lu tren luu vuc sdng Hucmg cin phai cd cac nghien ciiu tiip theo dua fren chudi s6 lieu dai narn hon, vdi sd team quan trie khi fcrgng - thuy van rdng khip va dl cap din nhidu yeu td hon.
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Tgp chi KHOA HQC OHSP TPHCM NguySn Hoang San
TAI LIEU THAM KHAO
1. Nguyin L^p Dan (2004), "Nghien cim ca sa khoa hoc cho cdc gidi phdp tdng thi du bdo phong trdnh lU lut a miin Trung", Bao cao t6ng kk khoa hoc va ki thuat, Ha Noi.
2. Dai Khi tucmg Thuy van khu vuc Trung Trung Bg, Ddc diim khi tuang thuy van khu vuc Trung Trung Bo ndm 1998, 1999, 2000, 2001. 2002, 2003, 2004, 2005, 2006, 2007. 2008. 2009, 2010, 2011. 2012. 2013, DaN^ng.
3. Cue Th6ng ke Thira Thien Hui (2014), Niengidm thdng ke 2013, Hug.
4. Truang Dinh Hiing (2001), Xay dung bdn do phdn viing ngap lut vd phuang dn cdnh bdo nguy ca nggp lut hg liru song Huang, song Bo tinh Thica Thien Hue, Bao cao ket qua de tai, Da NEng.
5. Nguyen Hoang Son (2003), Nghien cuu diiu ki^n sinh khi hguphiic v^phdt triin du lich tinh Thira Thien Hue, Lu^n van Thac sT khoa hpc. Hue.
6. Trung tam Du bao Khi tugng Thuy van tinh Thua Thien Hue (2001), Tap so lieu khi hgu tinh Thica Thien Hue, Hu^.
7. Phiing Diic Vinh (2001), Phdn tich vd ddnh gid che do mua, dm khu vuc Bac Trung Bo, L u ^ an Pho Tien sT khoa hgc Dia li - Dia chat, Truang Dai hgc Tong hop Ha Noi, Ha Noi.
8. Nguyin Vi^t, V6 Kim Tien (2004), ^'Cdc loai hinh the thai tiet gdy mua Ian a Thira Thien Hue ", Tuyen tap bao cao khoa hgc tai Hoi nghi khoa hgc khi tugng thiiy van nam 2004, Ha Noi,
9. Uy ban nhan dan tinh Thira Thien Hue (2005),,£)/a chi Thica Thien Hue - Phdn Tu nhien, Nxb Khoa hgc xa hgi. Ha Noi.
(Ng^y Toa so^n nh$n difQC b^i: 02-6-2014; ngdyphin bi$n ddnh gi^: 14-7-2014;
ngdychSp nh0n dSng: 20-8-2014)
