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BAD VE MOl TRUONG VA NGUON Lal THUY SAN • • Hai Phong, 14 - 15/01 /2005 ~ NHA XUAT BAN NONG N G H I~ P ABSTRACT INFLUENCES rqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA tham et phai AND SILTATION OF COASTAL OF CHANNELS a dayao che bien ON AQUACULTURE Nguyen Huu Cu, Tran Duc Thanh Hai PhongZYXWVUTSRQPONMLKJIHGFEDCBA In s titu te o f O c e a n o g r a p h y e ii cac vi EROSION C o a s ta l e r o s io n h e a v ily in flu e n c e d and s ilta tio n b y fis h in g T hough not recorded a c tiv itie s ; a n d d o c u m e n te d b e lie v e d to b e g r e a t in fo r m - decrease o f c h a n n e ls is c o m m o n in lo c a litie s in c lu d in g b r a c k is h a q u a c u ltu r e so fa r , e c o n o m ic w h ic h have been a n d m a r in e c u ltu r e lo s s e s d u e to th e s e p h e n o m e n a are o f" in th e a r e a o f a q u a c u ltu r e , _ c h a n g e in th e w a te r q u ~ lity , a n d e v e n le a d in g to d e g r a d a tio n o f s o m e a q u a c u ltu r e p o n d s , du luqng iuoi, dam lam kenh - r e d u c tio n in th e n a tu r a l s to c k , q u a n tity a n d q u a lity o f a q u a tic p r o d u c ts - a q u a c u ltu r e - u n -h a r v e s te d :lac bi~t la e 'sinh thai :hat thai tit in fr a s tr u c tu r e d e s tr o y e d b y e r o s io n , p o n d s d u e to e r o s io n - b r o k e n c a u s e w a y s in s to r m s a n d flo o d s ANH HUONG CUA XOI LO BO BIEN v A SA BOI LUONG LACH T61 NUOI THUY SAN Nguyen Htru Cir, Tran Dire Thanh P h d n v ie n H d i d u a n g h o c ta i H d i P h o n g MO DAU X6i 16 ba bien va sa boi luong lach la cac dang tai bien moi tnrong dia chat (tai bien cl~: chat)_ph6 bien vung be bien Viet Nam, gay hau qua kinh te - xa hoi nang ne bat chap ~h~g no, hrc ?hong tieuaclavanuacma-n) ~ " chon~ to Ian nhu hien nay, d6 c6 nuoi thuy san (nuoi thuy san , de0 tal "d' an h baat t h'uy san , tong he , va'a c hiirng rmrc nao qua su suy giam m nang nguon lei tv nhien, b" ' ;" X6i 16 Him h d' dan ve hi ,1c uan~ a lui dan ve phia luc dia, b01 tu, ngiroc lai, lam cho ba bien Ian x , tuang d~' : nuc; thu y bl:? ? , , •• '.' lach cac vung cira song va dam pha, va can bang 1a thay the theo mila voi cuong dQ nrong dirong d~u anh huang t6i hoac ,~6~ lap luong !~- bci XOI san duO! dang: (1) - thu hep dien tich nuoi ( ) - thay d,1· d:;'" ' 01 leu hen moi tnron g (3 ) _ nuOl, suy glam ngu6n gicng tu nhien, , , 77 (4) - khong 6n dinh nghe nuoi ca ve khong gian, thai gian (rnua vu) va doi tuqng nUai Bai vier de cap toi tinh trang xoi 10' be bien, sa boi luong lach va anh huang c' cluing toi nuoi thuy san thong qua cac phirong thirc khac ua TONG QUAN RQPONMLKJIHGFEDCBA V E XOI LO BO BIEN v A SA BOI LUONG L~CH 2.1 X6i la bb' bi~n 2.2 ~ TJ nang ( C chal 130 h, tritn v Tu - VungZYXWVUTSRQPONMLKJIHGFEDCBA b i r bien B a c B Vung bo bien B~c B¢ tir Mong O E (Quang Ninh) toi Lach Tnrong (bac Thanh H a ) gorn doan bo: Mong O E - Do San, Do San - Lach Truong M6i doan ba co hinh thai cau true moi tnrong dia chat khac nhau, co mat cac dia he khac va tat yeu tiern nan~ nuoi thuy san khac Doan ba Mong Cai - Do San dac tnrng boi vGng - vinh va vung cira song hinh pheu, noi co tiern nang nuoi thuy san 1< ;1 - man darn va nuoi hili san (mariculture) bang long be Dean be Do San - Lach Truong la ba chau th6 song Hong, noi co tiern nang nuoi thuy san ruroc 1< ;1 - nhat nhung kern 6n dinh boi nhanh pheu, ( hlnh It luong I o va dam bitn nh nguon la xoi 1,· bien Hi dang va Trong thai gian 1990 - 2000, co 30 diem xoi 10' bai trieu tir Mong Cai toi Cira Luc tren chieu dai 44 565m vci toe d¢ trung blnh 3,1 m/nam Chieu dai cac doan bo bi xoi 10trong khoang 420 - OOOmva toe xoi 10' khoang 1,4 - 8,0 rn/nam Tren dean ba Cira Luc - Do San co 15 di~m xoi 10' voi tong chieu dai 43 920m va toe d¢ xoi 10' trung blnh 4,4 rn/nam Chieu dai cac doan xoi 10' khoang 800 - 400m va toe d¢ xoi 10' khoang 1,2 - 12,9 m/nam Trong diem xoi 10' tren dean bo a cat Hai voi chieu dai 400Il} va toe d¢ 12,9 m/nam, a Phu Long (Duong Gianh) dai OOOmvoi toe 9,6 m/nam va Dlnh VG dai OOOmvoi tee d¢ 8,6 m/nam Doan be Do San - cira Ba Lat co diem xoi 10tren t6ng chieu dai 700m voi toe d¢ trung blnh m/nam Dean bo cira Ba Lat - Lach Truong co diem xoi 16 tren tong chieu dai 17 200m voi tee d¢ 14,5 m/narn Co the theo d6i dien bien xoi 10' cua cac doan bo bien ttr C U < l: Luc toi Lach Truong thai gian 19,30 - 2000 va dien tich mat di hang nam qua tirng thai ky tren bang - V u n g b o b iln T r u n g B m ot Oc Tinh) h i cira non delta tri, ap dao ( pha, tha: d o c luong - ( Can] dirng dal chi can n bao heat trieu rrr' ) o cat b6i Ian d Vung be bien Trung bo (tinh tir Thanh Hoa toi Ninh Thuan) co 275 diem xoi 10 tren chieu dai 328,16 km voi toe d¢ xoi 10' trung binh 11,9 m/narn va dien tich mat di 389,9 _ tinh rien; ha/nam (Pham Huy Tien va nnk, 2000) Dac bier thai gian 1999 - 2000, nhieu diem vung cat, xoi 16 day lui dirong bo tai 40 - 60m va tharn - V u n g b ir b iln n a m T r u n g B va chi toi 150 - 250m N am B9 Vung bo bien nam Trung B¢ (Binh Thuan) va Nam B¢ (toi Kien Giang) co 71 di~m x6i 16 tren chieu dai 478,12 km voi toe d¢ trung binh 2,5 m/nam (Bui Hong Long va nnk, 2000), co 12,8% chieu dai be bi xoi 10' voi toe d¢ 2,5 - m/nam, nrong U n g , 43,7% - - 10 m/nam va 43,5% tren 10 m/narn 78 ANH I THin Thon! thuy trieu b6i lu6ng ng nUaL Sa boi luong lach ua trinh phat trien chau th6 (delta), dirong ba tien dan ve phia bien bai boi TrO~gbi mat va me rong nhanh, dat toe d¢ trung blnh 27 m/narn (Ian nhat 120 m/nam) ~Anga~ath6song Hong, 50 - 80 m/narn (Ian nhat 150 m/nam) chai: th6 song Mekong va 2.2 .uOngRQPONMLKJIHGFEDCBA CUa ~3~ ha/nam rieng ban dao Ca Mau cac chau thd Ian nay, he thong lach trieu kern phat trien va chong tan he R6a) hlnh th"ai, tiern nang Tuy nhien, xoi 10 va bci tu lien quan chat che voi cac vung cira song hlnh ch~ng han vung cira song hlnh pheu Bach Dang va Dong Nai, qua trlnh san bang dia ~m:'luon xay theo ph~an,~ th"uc ~M ~uy bili trieu ca~: n:o r?n~.bil~ ;rie~ th~p v~ bdi lap juong Iach tao de cat chan Iui dan ve phia luc dia gay boi lap ca bai tneu lay va luong lach o mot so noi nhu Duong va d~m nuoi thuy san pheu, noi g long be ,i thuy san Gianh (Phu Long), de cat chan lui dan dil vui lap rirng ngap man vung cira song chau thd, xu the chung la bdi tu IAn tien ve phfa bien nhirng van dan xen C\1Cbo ( t h a i gian, khong gian) cac diem xoi 10 phan bo boi tich nguon luc dia qua bat doi ximg giira chu hru va cac ph an hru, Dien hinh cua tnrong hop ~ay la xoi 10 ba bien Hai Hau lien quan toi viec chan d~p song So Luong vat chat xoi lo'ba bien Hili H~u dll tham gia vao dong boi tfch doc be di chuyen ve phia tay nam gay bien dang va bdi lap ludng vao cang Hai Thinh ' o a Luc tren cac vung cira song liman, dien hinh la cira Lach Ghep (Thanh Hoa), Cira Khau (Ha 5i 10 ZYXWVUTSRQPONMLKJIHGFEDCBA Tinh) hay cira song Cu De (Da Nang), V.V.,boi tu co xu the dong kin cira va boi lap luong a Cira Luc cira nong dan ve mua kho dong boi tich cat d9C be tao roi cat phat trien tir mot phia va g blnh 4,4 delta trieu len v e mua mira, chinh cac t