Tin hoa da cht vung ca song bch dn

BQ GIAo-ovc vA DAo T~O TRuONG D~I HQC TONG H Hai Pho ng, 4,6 5,0 d9 Chuyen dong KTHD bi~u hien a d?c di~m bien d6i oe day va phan b6 tudng tram tich tren cac doi kien true, B'e day Holoxen ttr doi (1) den (3) tang dan : 0,7·2,8 m; 2·4m ; 4·9m va tang manh 11·14,8m d doi (4) Cac tram tich tirdng bi~n trieu thap va duoi trieu hau nhu chi phan b6 d cac ddi hin T6c d9 nang kien tao a ria nui, dao (doi 1) la 2,2·2,4mm/nam vao mra sau Q1V2; 1,2 mrn/nam vao dau Q1V3; 3,lmm/nam gill a Q1V3 va 0·0,5 mm/narn VaG cu6i Q1V:3 T6c d9 hin a ddi (4) Q1V2-3 khoang O,17·0,20mm/nam Bang phuong phap lap mire danh dau theo day ldp dam bi~n xam xanh Q1V3, da xac dinh diroc t6c d9 va huang van ng' kien tao tre n pharn vi phan b6 tudng bai trieu lay (dam lay bi~n) nhir sau : Ddi (1) nang 0,6 0,8 mm/narn Q1V:3; Doi (2) nang 0·0,6mm/nam Q1V:3; Ddi (3) 0·0,2mm/nam vao gil1a va cu6i Q1V3; Ddi (4) 0,2·0,8 mm/narn VaG cu6i Q1v3; 10 sn DO KitH TRUC TAN KIEH Tno KlfH TAO HIEN DR! VA BIE'U fflEN OJA CHAN VlING GUR ~6~wBRCJf nANG VR LnN CAN t- lIlgo'y IhlJ~nvach n."Jn t I , J 1,", - - ; J(len 190 vole;;'" 100 ll;f"d~7i lo~,1 t'd' bleu h,e" nong d'Pt' /roo ~ Irong /0;;' 100 hiell 001 s-> 100 II/dng clo; monh hn "0"9 Holo.ren co;'; cdo mallr;IJI va kiin ',?ohiindqico ' Jo PhiJdng II'''!,' cva dJI goy Irong ploo Oligoxen -Mionn (PJ -N,) PhtJdng (rlldl cva driI9'~Y Irong Plio.•• n - of/v (NI - Q) -* 10001 dong dot co /r."g 9101 bie" hirn cd"g dol', o eM;' 10m dpng da; d,?1 2.5 - R'-ch!er () cM;' o r, Ot1fgOj sou, ha,!,1 dpng Irong gioi doo» Tyen bi~n va dffy lui dirong bel Wi de>s8.U100-120m ngoai cira vinh Bac B9· 2.Tien hoa dja chat vung ei':tasOng Bach DAng Holoxen Qua trinh tien hoa lien quan chat che den biEin tien cha n tinh sau bang M Ian cu6i tre n ne n kie'n true hinh thai duoc thietl~p t11 trudc Lich s·J tien hoa duo c phan ba thai ky, mo i thai ky bat dau bang bi~n tien (hoac bi~n Ian) duo ng bo Ian v'e phia luc di a va ket thiic ba ng bi~n lu i, ducng bo Ian v'e phia bi~n M6i thai ky lai dircc chia tha nh cac giai dean M6i giai doa n ducc dac t rung bdi su t6n tai cac ki~u mo i t ruo ng tram tich nhat di nh 2.1 Thai ky thu nhat : Holoxen sdm giua (11-3 nghin nam truce) Bi~n 11 ti~n chan tinh giU vai tro chu dao gay ngap chirn, nhanh chong lam thay doi moi truong tit luc dia sang yen be, duong bo bj My lui xa nhat Vao cuoi thai ky, muc nude chan tinh dang cham him, vai tro kien tao va tram tich dU9C·tAng cuong, duong bo md Uln v'e phia bi~n, bi~n lui, G6m co giai dean : , - Giai doan : Mo! trtrong luc dia, Holoxen som - d'au Holoxen giira Qua t~IDh phong hoa, xam thuc chiem iru the Vao cuoi giai dean, bi~n tieri sat gan gay ngap chim khu bo ngarn hien va phat tri~n cac moi trirong aIuvi tich tu cat nho va moi truong h6 d'am tich tu bun set - Giai doan : M6i truo ng vinh - vun g yen bCJH~loxen giua : Bi~n tie~ tr~n ~g?P' ,md :9n~ nhat va dlly lui cu da n van hca Ti'en Hq Long khoi cac dao Vao nua dau giai doan to n tai ki~u m6i truong vi nh bi~n bai lay sii ve t (bai tri'eu lay) ba i tri'eu thap va phu ki~u ran san ho Sau thai gian 5600 narn, bi~n Iui va xuat hie n cac vung bi~n a ria phia bac va cac de cat bi~n (M 1) - Giai doan : Moi trirong d'am fay ria chau tM cuoi Holoxen giua Toc d¢ dang chan tinh cham h£n so voi nang kien tao a ria vung cua song (dat 2:4 m~l/nam) Cac khu vqc: ria VCS bi nang cao, phong hoa feralit ph6 bien D~m ,lay v~n bi~n t6n tai d trung tam vung cira song, nam d ria phia dong cua don~ Mng chau th6 song Hong Mt dau b6i tu manh Day la thai gian phat trien cue thinh van hoa RI,lLong, Trang Kenh 2.2 Thai ky thir hai : Holoxen muo n (3 den 0,5-0,7 nghin nam truce) Vai :ro chuyen d¢ng kien tao, d?t biet d cac ddi kieri true nang, tham gia quyet di nh VaGqua trinh ngap chirn, n6i cao Qua trinh tram tich tich cue co anh huang den huang di chuyen duong booVao cuci thai ky, b6i tu manh, d~ong bo di chuyen phia bi~n, qua ca khu trung tam sut kha manh Gorn giai doan : - Giai doan : Moi truong vinh - vung bien dau Holoxen muon Bi~n Ian trCill,likha nhanh Xuat hi~n vjnh bi~n nong d trung tam VCS d~ hl,lkien tI,lo kha ml,lnh c¢ng huang voi nfmg chan tinh cMm Cac Vl,lngbi~n nhO t6n tI,li a ria phia Mc tren dja pMn cac doi kien truc nang Phat tri~n cac dl,lngmoi truong biii trieu thap, bai trieu fay, bai bi~n va de cat bi~n (M 2) - Giai doan : Moi truong Vl,lngbi~n giua Holoxen muon Bi~n liIi b6i tl,l nwnh ket h9P voi nang kien tl,lOkha ml,lnh a cac khu ~ia tren n'en chan tinh dang cMm Phat tri~n r¢ng rai dq.ngmoi truong bai trleu fay su v~t tich tl,llOp bUn b9t xam xanh d?c trung va de cat bi~n (he 3) - Giai doan : Moi truong cua sOng chau tho, cu6i Holoxen muon Muc nuoc Mt d'au dang nhanh ca nang chan tinh va hl,lkien t?o nh~ng q~a 12 trinh b6i tu kha manh nguon cung cap b6i tich phong phu tU nguon goc song Hong Phat tri~n r¢ng khap bill b6i chau th6 ngap trleu cao hoa nhap vdi chau th6 song Hong rong' Ion Phat tri~n M de cat 2.3 Thai kYthii ba: cuoi Holoxen muon (khoang 0,5 - 0,7 nghin nam qua) Thai kY chi g6m mot giai dean dang tiep tuc vdi mot dot bi~n Ian mdi, duong' bOdi chuyen ve phia luc dia, ngap chim khong den bu tram tich, xoi Ib chiem uu the va qua trinh dam fay hoa manh me II BAN CHAT CAU TRUC vUNG ClrA SONG BACH DANG M?c du can co nhung y kien khac nhau, nhung da so cac nha dia chat cho rang cac estuary di~n hinh va ph6 bien thirong nam d hru song, co co cau true mra kin, thuong co dang hinh pheu, bi ngap chlm (do chan tinh va kien tao) kho ng d'en bu tram tich va thuy trfeu thuong co vai tro quan tro ng Vung cira sang Bach Dang co cau true la mot estuary (cira sang hinh pheu) dU9Chinh tren co sOtirong tac giita qua trmh phat tri~n cua mot graben dang sut chim vdi su nang cao cua mire mroc chan tinh, sir thieu hut b6i tich va thuy trieu co bien d¢ Ion Khang dinh dU9Cdira tren cac co Sd : Vung cira song Bach Dang co cau true mra kin cac kien triic tan kien tao va kien tao hien dai quy dinh Phan trung tam cua no narn tren mot graben sut kha manh Holoxen Vung cira song co dang pheu, thuc chat la t6 h9P ghep cua hai pheu Nam 'I'rieu va Yen Lap Vung ctia song Bach Dang dang a giai dean phat tri~n ngap chi m khong d'en bu thieu hut b6i tich Trong 5-7 tram nam qua, dang chan tinh dat 1.-1,5mm/narn, d b6n hi n trung tam kien tao kha manh, 0,2 - 0,8 mrn/nam Sl1 thieu hut b6i tich chu yeu giam nguon b6i tich cung cap tit song Hong va kha nang phan tan b6i tich trfeu va huang dong be i tich ven bo uu the DB-TN Day cling chinh la nguye n nhan co ban cua hien tirong xoi Id ph6 bien d viIng cua song Thuy tri'eu la yeu to d(ing I11Cngoq.i sinh uu the tM hi$n q1Jabien dQ, toc dQva thai gian dong tri'eu chay len xuong V.V dftn den tang cuong xam tht,tc va phan tan b6i tich ViIng cua sang Bl,lchD~ng la vlfCnuoc IQm?n, hoa tr9n nuoc song, bi~n kha tot tq.o nen st,t phan fang yeu th~ hi~n qua phan bo de>ml;in.Day la dfeu ki~n hq.n che b'oi t\1 va phat tri~n cac ba:itneu l'ay co thl1Cv~t ng~p m?n d?c trung cho vting cua song hinh pMu D?c trung tr'am tich, dia hinh chu yeu lien quan voi tri'eu so tuong tr'am tich dang tich t\1 chu yeu qua trinh tri'eu D?c di~m 13 di tram tich thuy trieu chi phdi, Cac dang dja hinh tlch tu va xarn thuc (tieu bi~u la bai trieu lay va h(l lach trieu) chii yeu lien quan den heat ng cua thuy trfeu phan Qua trinh bi~n thang the quan M tuong tac song bien th~ hie n qua sir Uti,the cii a x6i ld, ngap lu t, nhie m man, dam lay hca Theo phan loai dOng luc cua Leeder (1984), c6 th~ xep n6 vao ki~u B e6 cau true phan tang yeu Day la trtrcrig hop di~n hlnh tre n the gidi ve mot estuary phat t rieri dieu kie n nhat trieu bien d¢ ldn III- Q~A TRINH DlA DONG LTJC Hr:¢N NAY d vUNG ClrA SONG BACHDA.NG Trim nen kien true kien tao va chuyen dong kien tao hien dai dang tiep tuc, d VCS Bach Db.ng dang dien cac qua trinh d¢ng hrc chu yeu sau : D(mg 11!Cdi chuye n b6i tich vung Clta song Hoan hru b6i tich vung cua song dong trieu quyet djnh, sau la vai tro cua dong chay song, s6ng Ham hrcng, luu IUQngdi chuyen bo i tich 10 hrng bien d6i thea mua va quy luat thuy trfeu Dang chu y la hie n tuorig b6i tich di ohuyan nguoc sau vao vu ng cira song mua kh6 Hang nam c6 khoang trieu tan b6i tich cung cap ur song, tr ieu tan giai ph6ng tl! xarn thuc bo, bai va 3-5 trieu m3 bun cat nao vet luo ng lach tham gia vao hoan hru bo i tich vu ng cua song Qua trinh x6i Id, boi t u , Ngap chim kho ng den bu dieu kien thieu hut boi ttch Ia nguyen nhan sau xa cua qua trinh xo i la d vung cira song Xet tirdng quan ooi tu, x6i la thay rang hien d vung cira song qua trinh x6i Id thong trio Trong do, a trung tam vung cira song, qua trinh hin chlm kien tao co vai tro khong che Gan day su can thiep cua ngiroi da gay nen nhung bien dong bat thuong, phuc tap ve boi, x6i Khoang 50 nam qua (1938-1992), khu V1f.cLach Huyen - Yen Lap lien tuc bi x6i Id, khu V1f.cCua Cam - Nam Trieu b6i xoi xen ke phuc tap, X6i Id d muc trieu, thap r6 va manh hen d mUc trieu trung binh Mbi nam vUngcl1a sOng x6i Id 37 ha, b6i t\].27 va mat di 10 bill trieu cao ; x6i Id 31,5 ha, b6i t\] 4,5 va mat di 27 bai trleu tha'p Toc de>x6i Id bOdiio Cat H:ii (noi h~ l~n kha m~nh) trung binh 4-8m/nam, ctfc d~ 25m/nam Bo cac bai trieu fay x6i ld 0,5-2m/nam Noi ooi tl,lnwnh nhat la Trimg Cat d~t den 8m/nam, c6 lien quan den d~p d~p Dinh Vu nam 1981 d vung bo ngam, b6i t\] m~nh d d¢ sau I-3m, d~t 1-3cm/nam Co dau hi$u bao man day d dO sau 5-6m d khu bo ngam Cat Hai, baa man day 14 1-3cm/nam T're n h(l thana' luong xay qua trinh sa bo i no ng dan day lien quan den qua trinh xam thuc ngang me ro ng luong Sa boi lu6ng VaG cang tang d¢t bien gan gan day nhung tac d¢ng tieu cue cua nguoi, d~c biet la viec d~p d?p Dlnh Vu nam 1981 'I'rudc day, lUQng nao vet luong 1-2 trieu 3m /nam du tri lucng sau 6-7m Hie n ' Iuonz nao vet 3-5 tr'i$u m /nam chi tri diroc luong sau 3,5-4m Qua trinh darn lay hoa d vitng cii'a song D6 la ket qua cua dang cao mire nude bi~n, ooi tu cham va su phat tri~n day dl[l.ccua thuc vat ngap man trim nen dat uct ngap trleu cao, dfeu ki~n thuy trieu bien d¢ Ion Tren cac bill trieu fay phat tri~n rong rai d VCS, ton tai moi trircng khtr, yem khi, tfch tu hru huynh cao tram tich day, d~ bj oxy hoa dieu kien kho can va thuc V?t ngap man bi chat pha Tac d(mg cua ngutri da trd tha nh mot nhan to dc)ng 11!c vung cira song Tac dong r6 net khoang 500 nam qua.zCac heat dOng quai de, Ian bi~n, d~p dap, ngan song, nao vet luorig, chit pha rung ngap man ": da d:1n den nhung thay d6i bat thuong ve bo i t4, x6i ld, gay mat can bang tl,! nhie n va sinh thai vung cira song \" b IV XU THE BIEN DONG MOl TRUONG DIA CHAT vUNG ClrA SONG BACH DANG Ve lau dai, qua trinh ngap chim kho ng d'en bu c6 th~ dan den vinh hoa VCS Qua trinh kho ng qua 100 nam neu du baa ve hieu ung nha kinh sir that Trang tucng lai gan, xoi Id tiep t1.,1C chiem iru the Tinh toan theo quy t~c Bruun (19.62,1983) cho thay dao Cat Hai tiep t1.,1C bi x6i Id 4-6,2m/nam, dong nam Dinh Vu 0,8m/nam, cac bill bi~n D6 Son 0,36-0,45m/nam Khu Trang Cat se b6i cham dan, cac doi cat ven luong' ngam c6 xu hucng bi pha huy va tich tu cat tiep tuc duoc tang cucng d ven bo duong 14 Luong VaGcang 6n dinh dan trang thai mdi sau d?p Dinh Vil N gap 11.,1t ven bo gia tang Truye n trfeu, nhiern man tiep t1.,1C anh huang sau VaGIlJc dia Rting ng?p m~n bi suy giam di~n tich ca nguyen nhan ttf nhien va nhan taco CHUONG VI MOT s6 DE XUAT \IE KHAI TRAc Hap LY TAl NGUYEN vA BAO vE MOl TRUONG vUNG ClrA SC>NGBACH DANG DUOI G6c DO NGHrEN CUD TrEN HoA DIA CHAT HOLOXEN Tien hoa dia chat Holoxen, dl[l.cdi~m cau truc va dieu ki~n dia dOng 15 luc anh hunng quye t dj nh den ban chat tir nhie n, tai nguye n VCS Bach Dang Van d'e khai thac hop ly tai nguye n, baa v$ moi truong can phai dua vao tc5ng hop cac dieu kie n tir nhie n va kinh te xa ho i Tuy nhie n, nhung d'e xuat tir dudi gee d¢ n ghie n cuu tien hoa dia chat Holoxen la mo t nhirng can cu rat quan tro ng d6i vdi khai thac, quan ly lanh th6 cda song DINH HUONG CHIEN LUOC SU DUNG HOP LY TAl NGUYEN vA BAa vt M61 TRUONG vUNG CUA S6NG BA.·CH DANG l tri~n md Ian tu nhien phia bi~n nsn can co ke hoach 000 ve, phuc h'oi va can giu ty I~ thich hop can d6i vdi dien tich dam nuoi Du lich yen bien 130 mot huang kinh te can dircc chu vi nhirng lei the nhieu mat va kha nang hill hoa cua no vdi baa v~ t\f nhien, sinh thai Khai thac mu6i bi~n, cat xay dung d VCS can phai co quy hoach 'hop Iy M co hieu qua, tranh tac d¢ng tieu cue den moi trircng M¢t so' di~m sa khoang nho kh6ng nen khai thac vi gia tang t6c d¢ xoi Id bOo Dinh huang khai thac tai nguye n t6i 'uu va lau bEm Phat tri~n hop ly va nang cao nang luc heat d¢ng ciia cum cang Hai n g, nuoi va khai thac nguon lei hai san, rung ngap man tre n co sd tri tai nguye n va can bang sinh thai, ket hop phat tri~n du Itch yen bi~n vdi baa v~ moi truong tu nhie n Nhung van d'e quan ly, bao v~ moi bi~n, nhie m man, ngap II,lt, nhiern b:1n true vurig ctra song va hien trang khai 130 nhung van de cap bach can d~t ve Djnh huang quan ly, baa v~ moi trucrig N gan ngua han cha xo i Id bo bi~n, tranh va han che nhitng bien d¢ng bat thirorig ve boi xo i, dac biet 180 sa boi Iuo ng ben Du baa cac tai bien va anh huang l?p cac gie i phap ung xir Chu tro ng hau qua cua hien ung dang cao muc bi~n Baa ve, tri can bang tu nhie n va sinh thai, phong tranh cira song a nhie m Dinh huang phan vung quy hoach khai thac till nguyen va baa v~ moi truong theo hai khu Vlf.C cira Cam - Nam 'I'rieu va Lach Huyen - Yen Lap II NHUNG VAN DE CV THE SU DVNG HQP LY TAl NGUYEN BAa vt M61 TRUONG vA Kha nang phat tri~n cang va van d'e sa boi luo ng : Ban chat cau true estuary cua VCS 130 tfen d'e xac dinh tfem nang to ldn phat tri~n cum cang Hai ng Djnh hudng uu tie n kinh te cang can phai dua tre n quan di~m phat tri~n lau b'en moi trucrig, han che a nhiern mo i sinh Sa boi luo ng co th~ chinh tr] neu hi~u r6 nguye n nhan va co che S\i dung tai nguye n bai trfeu Iay, lach trieu nuoi hai san Day 130 d:;tng tai nguyen quy gia, kh6ng gia tang Do thieu quy ho~ch, thieu cd Sd khoa hQc hi~u qua cac dAm nuoi hi~n thap va tai nguyen dat Uat co nguy cd ~n ki~t Can dAu tu ky thu?t M chuy~n huclng tMm canh thay cho nuoi quang canh heat dong kinh te, dan sinh d'eu phai tinh den kha nang anh hudng va bi cua cac qua trrnh ch~t pha lay cui, xoi Id bO, cat Ian v.v RNM d day khong co kha nang phat 16 III KHUYEN NGHl : Tiep can vdi no i dung dja chat moi truong va quan ly dai yen be, ttr ket qua nghien cuu va cac quan di~m da trinh b y, luan an neu met so' khuyeri nghi : Djnh hudng phat tri~n kinh te vung cua song 130 cang (thuong - nuci tro ng hai san - du Itch bi~n Can quan tam den nhirng van de cap bach ";e moi truong cang) nhu sa boi luong ben, xoi Id bo, baa v~ rung ngap man, nhiern Mn, ngap lut yen boo Can chu tro ng den van d'e tien hoa dia chat va dieu kien dia dQng luc vu ng cira song giai quyet van d'e nguyen nhan va bien phap ehinh tr] luong vao cang Dat ooi ngap trieu vung cira song 130 till nguyen quy, kh6ng gia tang nen khong th~ khai thac tran Ian thieu quy hoach nhir hien Can co nhirng bien phap, ehinh sach quan ly moi trirong hop Iy va co hieu lqc nh~m h:;tn che nhung tac d¢ng tieu cqc cua nguoi Can tien hanh danh gia, d\f baa tai bien dia chat vung c\ia song co nhung phudng M an ung xU' thich h