Nghiên cứu cơ sở khoa học và đề xuất các giải pháp khoa học công nghệ đảm bảo sự ổn định và độ bền của đê biển hiện có trong trường hợp sóng, triều cường tràn qua đê khảo sát bổ sung tài liệu về địa hình, địa chất, khí tượng

Hai Hau Id mdt huyen ven bien phia Ddng Nam thupe tinh Nam Dinh, nam trong khoang tir 20o00' ~ 20ol5'dp vT Bdc va 106oir~106o23' d6 kinh Ddng; phia BSc giap huyen Giao Thuy, Xuan Trudng,

BO KHOA HOC VA CONG NGHE

CHirONG TRINH KHCN CAP NHA NXTdC KC 08/06-10

B6 TAI: 'Nghien citu cff set khoa h^c va de xuat cdc giaiphdp khoa hpc cong nghe bdo dam sff Sn djnh vd dp bin cua de bien hi$n c6 trong tririmg hpp song, triiu cuing trdn qua di"

Ca quan chu tri: Trii'6'ng Dai hpc Thuy lpi

Chu nhiem Sk tai: GS.TS Ngo Tri Vieng

Ha n61, 2010

BO KHOA HOC VA CONG NGH$

CHirONG TRINH KHCN CAP NHA NUQfC KC 08/06-10

D£ TAI: "Nghien citu ca s& khoa hgc vd de xuat cdc gidi phap

khoa hoc cong nghe bdo ddm sif on dinh vd do ben cua de bien hifn CO trong truamg hffp song, trieu cir&ng trdn qua de"

Mas6:KC08.15/06-10

BAO CAO

K H A O SAT B 6 S U N G TAI LIEU ve DjA HiNH, BjA CHAT,

KHi TU'gNG THUY VAN 02 VUNG TRQNG BI^M NGHIEN CLTU

NAM DINH VA HA TTNH

Dito/

GS.TS.Ngo Tri Vieng

BAN CHU NHIEM

MVC LVC

CHU-ONG 1 BANH GIA DI^U Klf N D|A HINH, BjA CHAT, KHi TU'GNG VA

THOY HAI VAN VUNG BI^N NAM BINH ; 2

1.1 T6ng quan ve bd" biSn va dS biin Nam Bjnh 2

1.1.1 Bieu ki^n ty nhien 2

1.1.2 Bd- bien Nam Bjnh 2

1.2 Banh gia dl4u kipn khi tirp'ng thiiy hai van 4

1.2.1 Gio 4 1.2.2 Mua 4 1.2.3 Chi ao thuy triiu 5

1.2.4 Bao nhiet ddi 5 1.2.5 NiFvc dang do bao 6

1.2.6 Chi dp song 7 1.2.7 Vin chuyen bOn cMvadilu klfn hinh thdi bo-biln 7

1.3 Binh gia dilu kifn dja hinh bv biin v i de blln Nam Bjnh 12

1.3.1 Bjahinh tu- nhien 12

1.3.2 Be biin 12 1.4 Banh gia dilu ki^n dja chit nln vimg xSy dyng de biin Nam Bjnh 15

1.4.1 Khu vyc Hal Hau 15

1.4.2 Khu vyc Giao Thuy 16

CHU-ONG 2 BANH GIA BlfeU Klf N B|A HJNH, fljA CHAT, KHi TU-t^NG VA

THCIY HAI VAN VCING BI^N HA TINH 19

2.1 Gid*! thipu chung v l viing biin Ha Tinh 19

2.2 Banh gia dilu kifn khi tu-ping thOy hai van 19

2.2.1 Mu-a 19 2.2.2 Dong chay sdng 20

2.2.3 Bao nhiet do-i 21

2.2.4 Thuy triSu 23 2.2.5 Nu'ffc dang 23 2.2.6 Dong chay biin cat 24

2.3 Banh gia dieu kien dja hinh bv biin va de biin Ha Tinh 24

2.4 Banh gia dilu kien dja chit nln vimg xay dyng de bien Ha TTnh 26

2.4.1 Be bien Hoi TJidng - Nghi Xuan 26

2.4.2 Be Thach Ha - huypn Lpc Ha 27

CHU'ONG 3 KtT LUAN 28 Tai lieu tham khao 29

BANH GIA D i e u KlfiN 0|A H I N H , DjA C H A T , K H I T U - Q N G V A T H O V

H A I V A N V C I N G B I ^ N N A M 0 | N H

1.1 TSng quan v l bd- biin wi d i biin Nam Bjnh

1.1.1 Dieu k/?n ty nhien

Nam Sinh tilp gidp vdi biin Ddng vl phia Phia Ddng Nam vdi ddi bd bien dai

72 km, thupe dja gidi hdnh chinh cua 3 huypn: Hdi Hau, Giao Thuy, NghTa Hung Dipn tich cua 3 huySn ven biin hon 720 km2, chilm xdp xi 44% dien tich tu nhien Cila tilth

Tinh Nam Djnh c6 4 con sdng Idn chdy qua : Sdng Hdng chay qua Nam Djnh vdi chieu dai xdp xi 70 km, do ra biin Ddng qua cua Ba Lat Sdng Ninh Co ddi 60

km la chi luu bd httu cda song Hdng, phan luu tai cila Mom Rd, dd ra biin Ddng qua ciia Lach Giang Sdng Ddo ddi 33,5 km Id phan lim cda sdng H6ng, hpp luu vdi song Day t^i nga ba Dpc Bp, sdng Day chdy qua Nam Dinh vdi ehilu dai gdn

80 km, do ra bien qua cda Ddy Sdng Sd la nhanh sdng nhd nhan nude tir cuoi Sdng Hdng thdng ra biin Ddng qua cira Ha Lan

Hai Hau Id mdt huyen ven bien phia Ddng Nam thupe tinh Nam Dinh, nam trong khoang tir 20o00' ~ 20ol5'dp vT Bdc va 106oir~106o23' d6 kinh Ddng; phia BSc giap huyen Giao Thuy, Xuan Trudng, True Ninh, phia Ddng giap sdng Ninh Co, phia Nam vd Ddng Nam gidp Biin Ddng vdi dudng bd biin dai 27km

1.1.2 Ber biin Nam Bjnh

Bd biin Nam Dinh keo dai tir eiia sdng Hdng din ciia sdng Ddy Id mpt ddi bd biin phdng, dja hinh thim luc dja tucmg ddi don gian vdi cac dang tich tp liln chau thd, thoai ddn tir bd ra khoi Nhin chung bdi biin tinh Nam Dinh hpp vd thip khdng cd vat cdn ehe chdn (trir 2 bai Con Lu, Cdn Ngan cOa huySn Giao Thuy; Cdn Xanh, Cdn Md cua huypn Nghia Hung) Chieu rpng bai trung binh tir

(100~150m) cd noi khdng cd bdi biin, bien tiln sdt chan de (Hdi Lj, Hdi

Triiu, ) Cao dp teung binh (0.00 ~0.50), cd biet cd noi cao ttinh bai dudi LOO)

(-va cd the ehia thdnh 4 doan nhu sau (xem Hinh 1):

Doan 1: tit ciia Ba L?t din cua H? Lan ndm trong khu vpc bdi tp Doan 2: tit ciia Ha Lan din Con Trdn ndm ttong khu vpc xdi Id

Doan 3: tti Cdn Trdn dSn eda Lach Giang tuong ddi 6n djnh

• Doan 4: tir Cflra Ljch Giang den Cira Ddy ndm trong khu vpc bdi tp Trong dd doan bd biin Hdi Hdu bj xdi Id den 3/4 chieu ddi tit ciia biin H? Lan din Cdn Trdn, khu vuc xdi Id manh nhdt thu$c dja phdn xd Hdi Ly, Hdi Chinh, hien vin dang bj xdi mjnh, khdng cdn con cdt phia ngoai, dp ddc bd bien tir 2

- 3 % 1dm cho dudng bd trd nen tuong ddi didng, dpc theo hudng Ddng Bde - Tay Nam

1.2.1 Gio

Xdt trong b6i canh nghien eiiu cd thi ndi rdng Nam Dinh ndm trong khu vuc bat lpi ve khi h$u nhipt ddi gid miia Vl mua ddng, chju dnh hudng eda hp th6ng gid miia ddng bdc vdi cac hudng gid thjnh hdnh 14 Bde, Ddng Bde vd Ddng Vl mda he, chju dnh hudng eda hp thdng gid miia Tdy Nam, vdi cdc hudng gi'd thjnh

hanh la Nam vd Ddng Nam Hinh 2 bieu dien hoa gid theo cdc thdng dpa tiin tdi

li?u quan tedc nhilu ndm tji tt^un Vdn Lu

• : ^

-^ -^ = 1 ^

Hinh 1 Hoa gio theo cac thang tram Van Lu- - Nam Dinh

Cd thi thiy ring trong thdi ky gid mia Ddng Bdc tir thang IX din thang XII, hudng gid Bdc thjnh hanh hon cd va tdn sudt dao dpng tir 19,8 ~ 29,7%, tir thang I din thang IV hudng gid Ddng Bdc thinh hdnh hon cd vd tin suat dao dpng til 25,2~41,9%.Gid miia Tdy Nam ho?t dOng tir thdng V din thdng VIII vdi hudng gid Nam thjnh hdnh hon ca vdi tin suit tir 19,5 ~ 35,9%

1.2.2 Mva

Tai Nam Djnh miia mua tudn theo quy ludt ciia khu vuc Ddng Bdc bp: bdt dau tir thdng 5 din thdng 10, vdi lupng mua trung binh nam biin d6i ttong khodng

mua xay ra vao miia mua

Lupng mua trung binh thdng Idn nhat dat vdo thdng 9 vdi lupng mua bien ddi tir 350 ~ 400mm Lupng mua trung binh cdc thdng miia mua la 244 mm (xem Bang 1) Lupng mua trung binh cdc thdng mda khd ehi dat 48,6mm S6 ngdy mua trung binh nam Id 140 ngdy, sd ngay mua trung binh cdc thdng tuong doi dong deu, pho biin tii 9 ~ 15 ngdy

Bdng 1 Lu'p'ng mua trung binh thdng trf m Vdn L^ - Nam Djnh

IV 70,1

Nhu v^y cd the thdy rdng Nam Djnh ndm ttong khu vuc cd lupng mua vira, lupng mua phdn b6 tuong ddi ddng diu Vin dl mua lu tir sdng d viing biin Nam Dinh do vdy khdng nghi£m ttpng

12.3 Che dg thuy trieu

Chi dO thiiy ttilu d khu vuc nghien cihi ndm ttong chi dp ttilu vjnh Bdc Bp Id chi dd nhdt triiu vdi bi6n dp khd Idn vdi bien dp bien doi tir 1,5 ~ 2,0 m Muc nude triiu tai Vdn L^ vdi muc nude ttilu tai Hdn Ddu cd he sd tuong quan dat 95

% Chu k^ khodng 25 ngdy va ttong mOt ngdy cd ciing ed mOt dinh vd mpt chan triiu Muc nude triiu Idn nhdt tai Ba Lat theo ehu ky 19 ndm cd th8 dat tdi eao ttinh 1,75 m (h§ cao dO VN-2000)

Nhu vpy ttong dilu kien triiu cucmg kit hpp vdi nude dang thi muc nude trade de khd 16n, sdng do dd cd thi tiln sau hon do dieu kien dja hinh bai trade de thip va cd thi tdc dpng true tilp len d8

f.2.4 Baonhi^ta&i

Nam Dinh chju anh hudng true tilp hojc gidn tiSp cua bdo vd dp thdp nhi^t ddi, xay ra ttong thdi gian tir thdng 7 din thdng 10 Tir ndm 1990 din ndm 2000 ttong viuig da chju anh hudng cua tten 50 con bao Bdo thudng hinh thdnh tir phia tay Thdi Binh Duong, vupt qua Philippines vdo biSn ddng sau dd do bp vdo bd

vdo bd bien miln Bdc Vipt Nam gay dnh hudng trpc tilp hojc gian tilp din bd biSn Hai Hdu, tuy nhien cQng cd nhimg ndm cd hon 10 con bdo do bp nhu ndm 1964,1973,1989

Cd the nh|n x6t rdng Nam Djnh ndm ttong khu vpc chju dnh hudng thudng xuyen cua bdo vd dp thip nhipt ddi (xem Hinh 3) Bdo kit hpp vdi nude dang vd sdng Idn cd the gay nhihig tdc dpng bit lpi cho khu vpc bd bien ciing nhu Id nhiing cdng trinh bao vp bd biin tinh Nam Djnh

Hinh 2 Bu-vng di cua cac can bao tip 1950 - 2000 do bo vac vjnh Bac

Bp cho thay Nam Binh nim trong khu vyc trung tam cua viing anh hu'dng

f.2.5 Nirac ding do bao

Nude ddng trong khu vuc xdy ra khi cd anh hudng cua gid trong bao vd dp thip nhiet ddi Bd biin Nam Dinh ndm ttong khu vpc vjnh Bdc Bd nSn khi cd bao

d vinh Bdc Bp diu gay ra nude ddng, nude rut d viing biin Nam Djnh, khu vuc phia bdc con bao chiu anh hudng ciia nude dang, khu vuc phia nam con bao ehiu anh hudng cda nude riit Cdc con bao dp bp vdo cdc tinh Ninh Binh, Thanh Hda,

hpc Thuy Lpi cho thiy: ttong mdt s6 con bdo do bp vdo cdc tinh ndy trong cac ndm tir 1975 din 1989 gay ra nude dang tit 0,5 din Im t?i bd bien Nam Dinh Bao Damrey (sd 7, 2005) gay ra chiiu cao nude ddng quan ttdc dupe d Hdi H?u Id 2,05

m

Do bd bien Nam Djnh thip nSn nude ddng dnh hudng Uvc tilp tdi tuyen de bito.Thdi gian duy ttl nude ddng ttwig binh tir 5 - 1 0 tilng va dat dinh trong Idioang 1- 4 tilng Thdi gian nude xuing ttung binh tir 15 -20 tilng Nude dang nguy hilm nhit khi td hpp vdi thdi dilm triiu cudng

12.6 Che dg song

Bd bien Nam Djnh Id mOt bd biin hd, tucmg ddi thdng theo hudng D6ng Bdc - Tdy Nam, khdng cd dao che chdn d ben ngodi, bd biin thodi va thip, do dd sdng vdi dd gid dai truy6n trpc tiep vdo bd md khpng gdp vat cdn gd, gay tdc dpng manh tdi bd biSn eung nhu cdc edng ttinh bdo vp bd

Ch6 dp sdng d Nam Djnh ed ede ddc diem nhu sau (xem bieu dd hoa sdng tren Hinh 4):

- Vdo mua ddng, tir thdng 9 ndm trade den thang 3 ndm sau, song biin dii dpi hon mua he vdi nhiing con sdng cd chiiu cao tir 0,8~lm va chu ky song tir 7-10 s Hudng sdng thjnh hdnh la Ddng Bde tao vdi dudng bd mpt gdc biin ddi tir

30 - 45° Vdo thang 10, thang 11, sdng ket hpp vdi triiu cudng tao ra muc nude

uy hiep bd bien va cac cdng ttinh bdo ve bd

- Vao mua He, tir thdng 4 den thdng 8, cd rit it ngdy sdng biin dii dpi, nhimg ttong miia nay, cao con bao Idn thudng xdy ra, neu bao dd bp trite tiep hoac

d lan cdn thi sdng vimg bd rit Idn gay ra thiet hai ddng k l cho bd bien va cac cong ttinh bdo vp bd Chiiu cao sdng trang binh bien doi tir 0,65 - Im vdi chu ky 5 ~ 7s Hudng thinh hdnh ciia sdng trong miia nay Id hudng Nam vd Ddng Nam

12.7' V$n chuyen bun cat va dieu ki^n hinh thai bcrbien

Vdn chuyin btin cdt d khu vuc Nam Djnh phu thupe vdo ede ylu td dpng lue ven biin va chiu anh hudng true tiep lupng biin cdt tir cdc con sdng ttong khu vuc, chd ylu la sdng Hdng Hiu hit biin cat trong he thdng sdng Hdng dupe dd ra biin

la t?i cira Ddy d phia nam bd biin Hdi H|u Tuy nhiSn, ciing vdi vi$c bdi tu mjinh

mS nay thi xdi Id d bd bien Hdi H$u eung kha manh li?t

0 10 20 30

Hinh 3 Bilu dd hoa song theo cac thang vung biin Nam Bjnh

lupng biin cat hang ndm dupe dd ra biin, dudi tdc dpng eua sdng gid biin cdt dupe tich dpng d phia Ddng vd Ddng Bdc cda nhdnh sdng Hdng cdn ttong ede didng mua ddng bim cat dupe phdn bd d phda Tay Nam

Lupng bim cdt cua sdng Hing do ra bd biin Thdi Binh, Nam Dinh trong mpt ndm Id rdt Idn Lupng bim cdt ndy phan b6 khdng diu ttong cdc thdng, 91,5% lupng bim cdt v|n chuyin vdo mda lu vd 8,5% vdo miia khd Cd tdi 30% lupng bim cdt dupe vdn chuyin, ttong dd cd tdi 48% Id cat, 43% Id cdt pha set vd 9% s6t

se Idng dpng d vimg cflra biin va phdt triln thdnh cdc roi cdt (ndm d dp sdu dudi 2m) Phan cun l?i (70%) chd ylu Id dat s6t va biin edt lo lu-ng theo diing triiu ra khu vpc nude sau (ndm d dd sau til 2 - 30m)

Tren eo sd phdn tich cdc sd lipu thu;^ - hdi vdn, ban do dja hinh nhieu thdi ky, cac tu lipu dnh v$ tinh dd phan giai cao da thdi gian vd ede tdi lieu nghien euai khdc c6 lien quan, tinh ttjng cac cu:a sdng va vung ven bien Hdi Hau Nam Dinh ttong khodng thdi gian hon 90 ndm qua (1912-2003) dupe ddnh gid qui mo diln bien phat triln nhu sau:

Ddy Id viing bd bien thap ndm giGa hai cda sdng Idn Id Ba Lat vd Lach Giang, dudng bd bien ddi keo dai theo phuong Ddng Bdc - Tay Nam dang bi xdi

Id nghiSm ttpng ttong nhilu ndm qua

• Giai dogn nam 1912 - 1935: Viing boi tu manh diln ra tai khu vuc nam

k l cdc cira sdng Idn: tai cdc xa Giao Lac - Giao Long (Giao Thuy) va Thinh Long (Hai Hdu), keo ddi thSm 2 - 5 km Vimg bd biin xoi Id manh thudc dia phdn huyfin Hai Hdu, bdt dau td eura Ha Lan tdi dja phdn xa Hdi Hod, viing xdi manh nhit thupe dia phan cdc xa Hai Ddng - Hdi Ly vdi chieu rpng tii 300 ~ 350 m

• Giai dogn nam 1935- 1965: Vimg xdi Id chinh chuyin dan sang doan bd

biin huy^n Giao Thuy vdi ehilu ddi ving xdi tdi 15km, rpng tit 200 ~ 280m, thudc dja phdn cdc xa tir Giao Xuan, Giao An tdi Bach Long Tren dopn bd Hdi Hdu, viing xdi Id keo ddi tii xa Hdi Ddng tdi xd Hdi Triiu, ehilu ddi tdi 14,5km vd chiiu rdng tit 150-180m, rOng nhit tdi 350m Vimg bli tp dien ra chu yeu tren dia phan cdc xa Bach Long - Giao phong (Giao Thuy), Hdi Ldc - Hdi Ddng, Thjnh Long(Hdi Hdu)

doan bd Hai HJu-Giao Thuy, gdm cdc xd tir Giao Xuan den Giao Lam (Giao Thuy) vd tir Hai Lpc din Hdi Hod (Hdi H$u) Chiiu ddi tong cpng vung xdi Id tdi 33,5km Viing xdi Id manh nhit thuOc dja phdn cdc xd tir Hdi Ddng din Hdi Chinh, rpng trung binh tir 250-300m vd Idn nhit tdi 400m Viing bdi tp dien ra chd ySu tten cdc

doi cat ndm ke cdc cua Ba L?t va L?ch Giang

• Giai dogn ndm 1989 ~ 1995 : Hipn tupng xdi Id dd gidm do cae viing xdi

dd dat d6n chdn tuyen de biin Cdc dosm bd xdi Id vd bdi tp ndm xen ke nhau chieu ddi tir 1,5 - 2,5km Vimg bdi tp ndm tt6n dopn bd giiia huy^n Hdi Hdu vd Giao Thuy

• Giai dogn ndm 1995 - 2003 : Tuong tu giai d o ^ trudc, hipn tupng xdi Id

dd dupe hpn che do vimg xdi dd dat din chdn de bien Cac viing bdi tu vd xdi Id nhp ndm xen ke nhau tten cdc doan ngdn Vimg bdi tu manh diln ra phia Giao Thuy thupe cdc xd ndm ke cda Ba Lsit

• Vimg bd bien vd h? thdng de ke Hdi Hdu trong thai gian gdn day

Bd biin Hdi H | u hi xdi manh ttSn ehilu dai 17.200m, tdc dp trang binh 14,5 m/nam; Idn nhat 20,5in/ndm Den thdng 3/2000, da xdc djnh dupe Hdi Hdu cd 10,4km bd rit nguy hiem, do tinh xung yeu cua de ke vd mjt dp ddn cu tap trang cao sat bd Chiiu ddi 15,6 km en lai tam thdi dn dinh do da dupe ke be tdng theo

du an PAM (4km) hoac phia trade cd cdn edt chdn (11,6 km)

Dogn bd thupe xd Hdi Lpc: Dupe boi tu vdo miia he vd xdi Id bd eat vdo mua

Ddng t?o thanh cac vach dflmg cao 1 ~l,5m

Dogn bd thupe xd Hdi Dong: Ikm dau tien gidp xd Hai Lpc bd dang bi xoi Id

manh, 1dm sdp mdi de tao thanh vdch diimg 2m

Dogn bd thupe xi Hdi Lu: Cd 1,8 km doan phia Bdc tilp gidp tiac tiep vdi

biin nhd cac con cdt phi lao, dita djii rdng (50-100)m Phia ttong Id tuyIn d6 dit, dip cao khdng kd Sat Id bd cdt tu nhien da tao ra vdch ddc cao (0,6~l,0)m Khoang 1,2 km phia Nam Id doan bd Vdn Lu cd ke Idt mdi vd ke nhd 6 vudng

dupe cdng cd, tdn cao vd kd be tdng 750m theo dp dn PAM

Dogn bd biin thupe xa Hdi Chinh: Cd 1,6km bd dS tuyIn ngodi dd bj phd huy gdn nhu hoan todn, chi cdn sdt lai nln i& TuyIn de chinh dd dupe ke Idt mdi ttong

du dn PAM va dd hinh thdnh mOt tuyIn de trong cdch 200m Khodng gan 2km bd

de phia Nam cdn lai chua dupe k^ bdi tdn t?i ddi hpp c6n cdt cd ttong phi lao

Dogn bd Ihupc xd Hdi Triiu: cd 2km ddu tiSn dang bi spt Id nghiem trpng

Tuyen de ngodi dang bj phd ra d 3 cho Khodng 1,5km de pn lai phia Nam tuong

ddi on djnh, bdi phia trade cda tuyIn dd ngodi ed cdn cdt phi lao rpng 100m

Dogn bd thupe xa Hdi Ha: TuyIn d6 ngodi dd dupe be tdng theo du dn PAM, phia trade mjt ki cd cdn cdt phi lao thua rpng (40~70)m, dang xdy dung tuyIn de

du pbng phia ttong each khodng 200m Khodng 0,5km bd thupe lang Xuan Tnmg chi cd cdn cdt phi lao rdng 50m dp sdt tuyIn de ngodi vd chua dupe bS tdng nSn doan de ndy cd nguy co bj phd huy khi ttilu cao va sdng Idn dd vdo bd Vdch xdi

Id d bd edt tu nhien nay cao (30~50)cm Khodng 1,6km giiia xd Hdi Ha ed tuyIn

de ndm liii khodng 260m, dS chua dupe ke v phia trade de cd ddi cdn cdt rpng (50-100)m, vach xdi Id tu nhien d doan bd ndy eao (0,5~I,0)m.Khodng 1,3km doan cudi xdi Id tao vdch diing cao (0,5~0,75)m, khdng cd tuyen de du phng d phia ttong

Dogn bd xS Hdi Thinh: chua dupe ke va khong cd tuyen de du phng Khodng

3km bd phia Bdc cd dai cdn cat rdng (50~100)m dp sat de biin, xdi Id tao vdch dflng cao (0,8-l,6)m Thdng 10/1999 nude ttilu ddng eao cdng vdi gid miia thfli manh dd lam sat Id vd phd hiiy bd rit nghiSm ttpng vdi ehilu rdng tir (10-50)m Khodng 2,2km tilp theo bd cimg dang bj s?t Id manh tpo thanh vdch (0,6-l)m, phia trade d6 biin cd ddi cdn cdt rdng (25~30)m, md ddn v l phia Nam tdi 200m Doan cudi ciing cila xa Hdi Thjnh dang dupe bim cdt tich tp hinh nem phat ttiln ve phia Nam

13.1 Dja hlnh ty nhiSn

Dja hinh nhin chung bdng phdng thodi ddn tir Bdc xuong Nam vd dan ra biin, tuy

cd xen ke mdt sd vimg trOng thap, song cd thi phan 1dm 3 viing dja hinh tp nhien:

- Vimg chiem triing (Bdc sdng Ddo) gdm huy^n: Y Yfin, Vp Bdn, My Ldc

va cdc xd, phudng phia Bdc thdnh phd Nam Dinh

- Vimg ddng bdng vd vimg ddng bdng ven biin ndm phia Nam sdng Ddo gdm cac huy^n: Nam Trpc, Trpc Ninh, Xuan Tradng, Giao Thuy, Hdi Hdu, NghTa Himg

- Vimg bai bdi ven biin t|ip trang d eiia sdng Hdng (bai Cdn Ngan, Cdn Lu) thupe huyen Giao Thuy eda sdng Ninh Co, cu:a sdng Ddy (Ddng, Tdy, Nam Diln, Cdn Xanh) thupe huy^n Nghia Hung

Cao ttinh dit tp nhien ph6 biin til + 0,75 - +0,90, nhirng khu vpc eao ed cao trinh tir +2,0 - +2,5 vd nhiing khu vpc thip cd cao ttinh tir +0,30 - +0,40 0 khu vuc Hai Hdu them luc dja tuong dfli die hon, bai bien cd dp ddc binh qudn tir

1 ~ 2% ttong pham vi 200m tir chdn de sau do thodi ddn, cae dudng ddng miic chay song song vdi bd biin

Tuyen de biin tinh Nam Dinh dupe hinh thdnh each day khodng 250 nam

-300 nam Tuyen dd biin ed nhiem vu bao vp cac huyen: Giao Thuy, Hdi Hdu, NghTa Hung, Xuan Tradng vd 6 xa phia td sdng Ninh Co eua huyen True Ninh vdi tdng difn tich tir nhiSn 87.128 ha, ttong dd dipn tich canh tdc 52.198 ha chilm 59,%, tdng s6 ddn 923.500 ngudi Viing dnh hudng true tilp cua tuyIn d6 biin Nam Dinh Id 38.300 ha dit tp nhien trong dd cd 23.850 ha dit canh tdc vd tinh mang, tai sdn cua 536.200 ngudi ddn sdng trong khu vuc ven biin tliupc 3 huy$n Giao Thu^, Hdi Hdu vd NghTa Himg

13.2 Debien

De biin Nam Dinh ch^y theo 2 hudng: de Giao Thu^ chay theo hudng Bdc Ddng Bdc, d6 Hai hdu chsiy theo hudng Ddng - Ddng Bdc vi vdy ttong thdi ky miia mua hay miia khd, diu chju dnh hudng do gid miia Ddng Bdc hay gid miia Ddng Nam Tdng chiiu ddi tuyIn de bien Nam Dinh Id 91,981 km trong do: tuyIn

-Hdu ddi 33.323 km(vdi 20,5km tt^c difn vdi bien), tuyIn de NghTa Hung ddi 26,325 km (vdi 4,8 km tt\rc difn vdi biin) Ba tuyIn de ndy dupe ndi tilp vdo cdc tuyIn de hiJu sdng H6ng, de td - hihi sdng Sd, de ta - hOu sdng Ninh Co vd de ta sdng Day tao thdnh mpt h? thdng de kh6p kin bdo vf vung trpng dilm kinh tl, xd hpi vimg ven biin Nam Djnh

Cdc doan de d viing ciia sdng: cd ting chiiu ddi 28.648m, thdn dd chd ylu dupe ddp bang dat thjt, dat pha cdt quy md nhd vd thip phia ngodi sdng cd bdi bdi nhung cao ttinh m^t bdi thip tir (0.00 - +0.30) Khi thuy triiu len hdu hit bdi bi ngap sau nude bien tt^c tilp tdc dpng vdo thdn de, khi gdp bdo Idn, sdng biin ttdn qua mdt de Cao ttinh de (+3,60 - +3,80), ehilu rfng mdt de (3,30 - 4,00 m), he sd mdi mb = 1,5 - 2,5m; mj = 1,0 - 1,5

Cac doan de trpc difn vdi biin: cd ting ehilu ddi 50,8km, thdn de ehu yeu ddp bang dat thit pha cdt, mdt cdt ngang mft sd doan nhd, cao trinh dinh thip vd hi sat

Id

Bdi bien ngodi dd thdp vd hep do bi xdi mdn lien tue, khi thuy trieu xuong bdi

rpng tnmg binh 100 - 150 m, nhilu do?n khdng eon bdi (Hdi Lj, Hdi Triiu, Hdi

Chinh) Khi thuy tridu len bdi hi ngdp sdu, sdng vd ddng chay ven bd thudng xuyen tac ddng true tilp vdo de gay xdi, spt Id mai, nghiem ttpng nhit Id khi cd bao vao hoac nhiing con gid miia Ddng Bac

Nhin chung de biin Nam Dinh hien dang d eao trinh kha thap phd biin ndm d cao ttinh +4,0 m 0 mdt s6 doan de mdi xay dpng cao ttinh dd da dat cao trinh 5,50 m, phia biin dupe gia cd bang khdi Tse bd day 2 0 - 3 0 cm, mai phia ddng ttdng cd vetiver ttong khtmg da xdy Tuy nhidn d mpt sd noi mdi dd biin chua dupe gia c6 d l dam bdo didu kien chdng xdi dudi tdc dpng eua sdng ttong bao Xin dac bidt luu ^ rdng d nhieu doan dd mdi hipn nay tinh hinh xam thue dn mdn cac ciu kidn bd tdng mdi phia biin Id ddng bdo dfng Nguyen nhdn cd thi Id do chit lupng thi cdng cdc ciu kipn ndy tji chd khdng ddp irng ydu cdu vd cudng dp chdng mdi mdn

TuyIn dd biin Giao Thuy dai 32,333 K m , c6 9 ke ddi 6829 m, cd 9 dilm canh

dd vd 14 cdng Tir ndm 1962 - 2000 t?i KI5,5 - K20,5 dd phdi di ddi 3 Idn Cao ttinh dd: hien tai cdn mft so dojn thilu eao trinh Dopn tir KO - K12+600 cao dp hifn tai chi dat (+3.15 ~ +4.10) thilu cao ttinh tir (1,40 ~ 1,80 m) Do?n tir K25+091 ~ K29+274 ed nhilu ehd eao dd hifn tai djit (+3.40 ~ +4.00) thilu tir ( 1 , 0 - 1 , 6 m) Mdt cat tit ca nhttng doan dd ttdn diu nhd hon thilt kl

Chat lupng dd: Do dupe tdn cao dp true nhilu Idn ttong nhilu th^p ky, tir nhieu thd hp nen chat lupng de khdng dupe ddm bdo, mjt dd bj cdy xdi do cdng n6ng di l?i MOt sd d o ^ dd dupe ddp bdng cdt bpc dit thjt (dojm tir K22+400 - K27+161), mjt vd mai de bi nude mua xdi thdnh rdnh Idm thu hpp mjt cdt dd cpc bf cd chd chi cdn xdp xi 3,0 m mdt dd nhu doan Giao Phong - Giao Lam

Ndm 2006 do dnh hudng cua bao, dp thip nhipt ddi vd nhihig dpt ttilu cudng kit hpp vdi gid miia dd 1dm kd Ddng vd Tdy cdng Thanh Nidn thudng xuydn bi sat

Id

Ndm 2007 Triiu cudng kdt hpp vdi sdng dd 1dm nhieu do?n dd, kd sat Id nghidm ttpng, tao ra 21 hd an sau vdo thdn dd De kd Ddng va Tdy cdng Thanh Nien dupe xdc dinh Id ttpng dilm xung ydu

1.3.2.2 TuyIn de bien Hai Hau

TuyIn de biin ddi 33,323 Km cd 10 ke ddi 17.611 m, cd 6 didm canh dd vd

23 cdng qua dd Ddc dilm cua dt biin Hdi Hdu Id ndm d viing biin tiln, de dupe

dip bdng cat b p c d i t thjt Chi tinh tii nam 1986 - 2000 dd bidn Hdi Hdu da bi tdn pha 11.900 m

Ndm 1989-2000: dd Hai LS, Hii Chinh (KIO ~ K14) ddi vdo ttong tdi 3 lin

Nam 1971- 1994: dd Hdi Hod (K17,5 - K18,8) di ddi 3 lin

Ndm 1926 - 1972: dd Hdi L^ ( K7 ~ KIO) di ddi 3 Idn

Tir nam 1996 - 2000 du dn PAM da phdi diu ttr 123.384 m' dit, vd 37.432 m'

da ke eac loai