Tiiu han Cdc Khoa hoc vi Trdi ddt ISBN 978 604 913 016 8 DAC DIEM CAU TRUC DAM PHA LIEN QUAN T 6 I THIEN TAI 6 VEN BIEN MIEN TRUNG VIET NAM STRUCTURAL FEATURES OF COASTAL LAGOONS RELATED TO NATURAL HA[.]
Tiiu han: Cdc Khoa hoc vi Trdi ddt ISBN: 978-604-913-016-8 DAC DIEM CAU TRUC DAM PHA LIEN QUAN T I THIEN TAI VEN BIEN MIEN TRUNG VIET NAM STRUCTURAL FEATURES OF COASTAL LAGOONS RELATED TO NATURAL HAZARDS IN CENTRAL VIETNAM Nguyen Hfloi Cu Vien Tii nguyen v i Mdi trudng bien 246 Da Ning, Ngd Quyin, Hii Phdng Tom tat: Dam phd, mot nhirng logi hinh thiiy vuc ven biin, phd biin a nhiiu nai trin thi gidi, chiim khodng 13% chiiu ddi ba biin Viet Nam cd 12 dam phd tiiu biiu phdn bo a ven biin miin Trung khodng tir Uo vi bdc (Ninh Thudn) tai 16o vibdc (Thira Thiin Hui) vai mat 57 km chiiu ddi ba biin miin Trung cd dam phd vd ba dam phd chiim khodng 21% chiiu ddi ba biin Viet Nam Hi thong ddm phd ven biin miin Tning Viet Nam la cdc lagun ven biin vi thdp, nhiet dai ndng dm, khdc vi kiiu logi (gdn kin, kin tirng phdn, ddng kin), vi kich thudc (tir nhd - diin tich mat nuac dual 10 km2, tai lan - diin tich trin 50 km2, thdm chi trin 200 km2 vd thudc logi lan cua thi giai nhu hi dam phd Tam Giang - Cdu Hai), vi ddc trung khdi nuac (tir Ig - nhgt tdi Ig - man, thdm chi siiu man), v.v., ddc biit khdc vi dgc diim cdu tnic hinh thdi liin quan tai tai biin tu nhiin viing ba biin, dd cd biin dgng cira ddm phd, lu vd ngap lut ddng bdng ven biin, nhiim man vi miia khd, nggt hod vi miia mua, v v Ddm phd cd bdn hgp phdn cdu tnic ca bdn: vuc nuac, cira, di cdt chdn vd ba sau Hinh thdi vd tinh dn djnh cua cdc dan vi cdu tnic thay ddi qua cdc giai dogn phdt triin cua ddm phd vd phu thugc vdo ngudn gdc dam phd hinh thdnh qud trinh san bdng ba vung vjnh hay ldp ddy cung bdi tich bdng ca chi phdt trien chdu thd.Su thay ddi ciia cira dam phd Id mdt nhirng dgng tai biin gdy hdu qud kinh ti-xd hdi vd mdi truang ndng ni cho cdc cdng ddng ddn cu ven biin Abstract: Coastal lagoons, one of the kinds of coastal waterbodies, are common in the world, bordering some 13 % of the total world coasline There are 12 typical coastal lagoons in the Centre of Vietnam in a range of 110 N (Ninh Thuan) 160 N (Thua Thien Hue) They appear on 21 % of the Vietnam coasline with a density of one lagoon in every 57 km of the Central coasline They are the tropical low-latitude coastal lagoons diverse in typology (nearly enclosed, partly enclosed, and enclosed); in dimension (from small size with an area less than 10 sq.km to large size with an area more than 50 sq km, and even more than 200 sq km ( Tam Giang - Cau Hai lagoon as a large one of the world)); in salinity (from oligohaline, mesohaline, polyhaline, to euhaline, and even hyperhaline); especially in stmctural features in relation to the coastal hazards, among which are instability of lagoonal inlets, flooding and inundation, salt-intnision in dry season, desalination in rainy season, etc A coastal lagoon is composed of parts of basin, inlet, frontal barriere of sand and sheltered shore, which have changes in morphology and stability dependent 226 Hgi nghi Khoa hgc ky' niem 35 ndm Vien Khoa hgc vd Cong nghe Viet Nam - Hd Ngi 10 1010 on lagoonal development in stages and lagoonal formation related either to the process of equilibrating bay and embayment coasts or to the deltaic progradation The change of lagoonal inlets is one of the natural hazards with heavy socioeconomic and environmental effects occurring to coastal communities MO DAU Dim phi (coastal lagoon) li mdt cic loai hinh thuy vyc ven bien tieu bieu cimg vdi cae vimg cira sdng vi viing vjnh, ddng thdi la mdt bd phin eiu triie ria ddng bing ven bien Sau hinh thinh, dim phi trii qua eic giai doan phit trien eua minh tir giai doan tre (active), giai doan trudng thinh (grown), tdi giai doan suy tin (ephemeral) vi chet (dead), rdi trd viing triing thip (polder) dudi dang tram, bau nude nggt, dim liy, v.v Trong qui trinh phit trien md rdng ddng bing ven bien mien Trung Viet Nam, ed mat nhieu dim phi ed ldn nhd da tin vi hiu bet eic dim phi hien dai ed ljeh sir hinh thinh tir Holocen giira (Nguyen HQ-u Cir, 1995) Hau bet dim phi li bdn hdi luu cic sdng cd chirc ning dieu tiet lii d mire nhat djnh, nhung ddng thdi li tie nhin giy ngap lut ddng bing ven bien de cit chin ngoai va cira hep Trong nhieu trudng hgp mire neap lut ldn, ap lye thuy tTnh giy hire xung (thixotropy) phi vd de cit tao cira mdi va thim ••• nhieu cira nhu d he dim phi Tam Giang - Ciu Hai trin lu lich sir vio thing 11/1 >'v, 'im phi ed bdn hgp phin eiu tnic CO bin - vyc nude, de cit chin, cira vi bd sau Tiong ML.: .iinh phit trien dim phi, nhieu dang tai bien ty nhien ed lien quan giy hiu qui kinh te-xa hdi ning ne eho edng ddng din eu ven bien Bai viet niy cd mue dich phin tieh die diem eiu tnic dim phi lien quan tdi tai bien ty nhien lam co sd khoa bge de xuit irng xir tai bien d ven bien mien Trung Viet Nam TONG QUAN VE LAGUN VA DAM PHA VEN BIEN MIEN TRUNG VIET NAM Tir lagun ndi chung (lagoon, lagune, laguna, v.v.) ed ngudn gdc tir ehii latin - lacuna, dugc sir dung tuong ddi rdng rai de chi eic ddi tugng khie Trong tir dien "Glossary of Geology, 3"^ ed., 1987", lagun dugc hieu li mdt bd phin dugc tich khdi mdt vyc nude nhd mdt dang tieh ty chin ngoai Nhu viy djnh nghTa niy rit rdng, bao gdm ci lagun xa bd (offshore lagoon) va ven bd (coastal lagoon), ei vyc nude man vi nude nggt O Viet Nam, ed mat cic lagun xa bd quy md nhd nhu d quan dio Trudng Sa im tieu san hd tao thinh, ed lagun ven biin d miln Trung Viet Nam, cd lagun ven bien nude Ig, nude man vi thim chi sieu man (Dim Ling Cd, Dim Loan) nhung chua he ndi tdi lagun nude nggt cd ngudn gdc sdng hoac hd nhu djnh nghTa ndi tren Lagun ven bien, nhu cd mat d ven bd mien Trung Viet Nam, cd khii niem hep hon lagun ndi ehung, dugc xie djnh li: mdt thuy vyc ven bien, duge ngin cich vdi bien nhd mdt dang tieh tu cit chin ngoii, in thdng vdi bien phia ngoii qua mdt hay nhieu cira hoac tham thiu (percolation), chay thim (seepage) qua ehinh the eit chin Trong sl cic djnh nghTa lagun ven bien hien nay, djnh nghTa eiia Phleger, F P (1981) dugc sir dung phd bien hon - lagun ven bd li mdt loai hinh thuy vyc ven bien nude Ig, nude man hoac sieu man, duge chin bdi mdt de eit va cd cira (inlet) in thdng vdi bien phia ngoai Ten ggi dja phuong ve lagun ven bd tdn tai mang tinh Ijch su va tap quan, cho tdi da trd thinh danh tir rieng va viet hoa Vi du nhirng lagun ven bien ndi tieng cd ten ggi ljeh sir li hi - H I Mat Trdi (Solar Pond) d Israel, Hi Togo (Lac Togo) d Guinea, Ho Mellah (Lac Mellah) d ven bd ddng Dja Trung Hii, li vjnh - Vinh Roekport (Rockport Bay) d Texas hay Vinh Florida (Florida Bay) - li lagun ven bien dien hinh tao bdi eic ran san hd chin ngoii 227 Tiiu ban: Cdc Khoa hgc vi Trdi ddt ISBN: 978-604-913-016-8 (2> Viet Nam, cic lagun ven bien duge ggi li "dim" hoac "phi" Vi du, d Thira Thien Hue cd ten ggi phi Tam Giang, dim Sam, dim Thanh Lam, dim Hi Trung, dim Thuy Tu vi dim ciu Hai, ma tit ci ehung li nhirng thiiy phin khdng ed ranh gidi ty nhien hgp thinh mdt lagun ven biin thong nhat Ngay tir xa xua, thu tjch cd eiing nhu din gian, tdn tai nhilu ten ggi theo ranh gidi hinh ehinh, ed ten phi Hii Hac, phi Tam Giang, dim Nieu, dim Da Di, vjnh Ddng, vjnh Minh Luong vjnh Hung Binh, vjnh Giang Tan, vjnh Ha Bac, v.v Cho tdi nim 1831 (thdi Minh Mang), mot sd dugc ddi ten thu tjch thinh Dim Thanh Lam, Dim Hi Trung, v.v nhung din gian vin giir eich ggi rieng vi ngiy vin ggi tit la phi Tam Giang - Cau Hai va thim ehi ggi phi Tam Giang Cimg ddi tugng dd d Quing Ngai cd ten ggi dim An Khe hay Dim Nude Man (Sa Huynh), d Binh Djnh ed ten ggi dim Tri 6, dim Nude Nggt hay dim Thj Nai, d Phii Yen - Khinh Hda ed ten ggi dim O Loan va thim ehi dim Nha Phu mi dim Nha Phu li mdt vjnh ven bd (bay) dien hinh Trong dd, d nhieu noi khie sir dung ten ggi "dim" theo truyen thdng de ehi mdt loai hinh thuy vyc ty nhien, tao mdt doan sdng chet, mdt viing trung cdn sdt lai qua trinh phit trien ddng bing ven bien cd lien quan tdi qui trinh liy hda hien Loai hinh tuong irng vdi "trim" vi "biu" theo cich ggi ten d mien Trung Hon nira, ehinh ngudi din ven bien ty tao mdt loai hinh thiiy vyc viing trieu (quiy dap mdt phin bii trieu) de nudi thiiy sin nude Ig roi Cling ggi nd li "dim" Do dd, de tien lgi va nhim phin anh diing ban chat ciia mdt he ty nhien, chiing tdi de nghj sir dung ei tir dja phuong ed viet hoa - Dim Ciu Hai, Phi Tam Giang, vi tir khoa bge da phien im tieng Viet mi khdng viet hoa - lagun Khi de cap tdi mdt van de khoa hgc thi diing tir phien im vi de cap tdi ddi tugng eu the thi diing tir dja phuong Ching ban, he Dam phi Tam Giang - Cau Hai li mdt lagun ven bien, hay qui luat phin bd trim tich day Dim Loan bieu hien mdt lagun ven bien dang phat trien d giai doan trudng thinh, v.v Vin de phin loai lagun rit phire tap va ei phin biet giiia lagun, vjnh vi viing cira sdng ciing khdng de bdi tinh chuyen tiep giiia ehiing Tuy nhien, cd thi phin loai theo vj tri tuong ddi tren them lue dja thinh lagun xa bd vi lagun ven bien Lagun xa bd duge hiiu la mdt phan cua bien hoac dai duong dugc tich nhd im tieu vdng (atoll) Sy phit triln ciia ehiing khdng bj inh hudng bdi eic qui trinh luc dja Lagun ven biin duge bilu la mdt phin eua bien ven bd, duge tieh nhd mdt dang tich Ui thudng li cat, hiim li im tieu viin bd Sy phit trien eua lagun ven bien phuc tap bdi tuong tic giGa cic qui trinh biin (sdng, thuy trieu vi ddng chiy) va lyc dja (sdng, van ddng kiln tao khu vuc, v.v.) He thdng phan loai lagun ven biin eua Nichols, M and Allen, G (1981) khii quit hon va duge su dung rdng rai hien He thing phan loai dya theo nguyen tie ddng lye, phin anh ddng lye hinh thinh va phit trien lagun the tuong quan giiia eic qua trinh biin (sdng, ddng chiy, thuy trilu) vi cie qui trinh lue dja (sdng) thdng qua hinh thii va qui trinh uu the lagun He thdng phin loai niy chia cie lagun ven biin dai duong thi gidi thinh bdn kieu: lagun cira sdng (esUiarine lagoon), lagun hd ("open" lagoon), lagun kin timg phin (partly closed lagoon), lagun ddng kin (closed lagoon) O Viet Nam, eac lagun hien dai tieu bilu phin bo d ven biin miln Trung dugc chia thinh kieu (Nguyen Hiru Cir, 1995) nhu sau: kilu gin kin (nearly-enclosed), kilu kin tirng phin (partly-enclosed), kilu ddng kin (enclosed) Vj tri tuong ddi cae kieu cua hai each phin loai khdng hoan toin triing khdp mac dii ciing nguyen tic phan loai ddng lue - hinh thii Kilu gan kin d day mang ei hai ylu tl "hd" vi "kin timg phan" cic nguyen nhan dja phuong tao 228 Hgi nghi Khoa hgc ky- niem 35 ndm Vien Khoa hgc vd Cong nghe Viet Nam - Hd Ngi 10 2010 CAU TRUC HINH THAI D A M PHA LIEN QUAN T I THIEN TAI 2.1 Kich thirac cabdn cdc ddm phd O ven bien mien Trung Viet Nam khoing vT 11° - 16° bie, cd mat 12 dim phi tieu bieu vdi tdng dien tieh mat nude 436,9 kml Cie dim phi niy da dang ve kich thudc (bing 1), dd, nhd nhit li Dim Nude Man (Sa Huynh) cd dien tich 2,8 km^ ldn nhit la he Dim Phi Tam Giang - Ciu Hai (Thira Thien Hul) vdi dien tieh 216 km^ ldn nhit Ddng Nam A vi thude loai ldn cua the gidi Theo thir ty vl phia nam, he thdng dim phi bao gdm: he Dim Phi Tam Giang - Ciu Hai, Dim Ling Cd (tinh Thira Thien Hue), Dim Trudng Giang (tinh Quing Nam), Dim An Khe, Dim Nude Man (tinh Quing Ngai), Dam Tri 6, Dim Nude Nggt (Degi), Dim Thj Nai (tinh Binh Djnh), Dim Cii Mdng, Dim Loan (tinh Phii Yen), Dim Thuy Trilu (tinh Khinh Hda), Dim Nai (tinh Ninh Thuin) Bdng Diin tich vd kich thuac cdc dam phd ven biin miin Trung Viet Nam (N H Cir, 1996, 1999) (cd bd sung theo tdi lieu khdo sdt vdo thdng ndm 2005) TT Dam pha Dien tich (km^) Kich thudc (km) Dai Rong Do sau (m) Trung LOTI binh nhat Tam Giang Cau Hai 216 68 - 10 1,6 4,2 Lang Co Tmdng Giang 16 36,9 6,0 10,0 3,5 5,0 1,2 1,1 2,0 2,0 10 11 12 An Khe Nude Man TraO Nude Ngot Thi Nai Cii Mong Loan Thuy Trieu Nai 3,5 2,8 14,4 15,6 50 30,2 18 25,5 3,0 3,0 6,0 8,5 15,6 17,6 9,3 17,5 1,1 1,0 2,5 2,5 3,9 2,2 1,9 0,3-3,0 3,5 1,3 1,0 1,6 0,9 1,2 1,6 1,2 1,5 2,8 1,6 2,2 1,4 2,5 3,5 2,0 4,0 3,2 Kich thuoc ciia (m) Dai Rong Sau Thuan An :6000 Tu Hien: 100 1000 An Hoa 500 Tam Hai 400 3000 300 5000 2000 1200 500 6300 1000 2500 350-50 2111 150 400200 -8 150 120 150 125 900 350 50 1000 500 1,5 -4 1,6 1,5 4,0 4-6 2.2 Dgc diem cdu tnic ddm phd He thdng eac de cit chin tao nen dim phi ven bien mien Trung Viet Nam deu li cic dang tich tu cit ndi dio qui trinh san bing bd viing vjnh hoac lip diy eung bd theo co che phit trien ddng bing chiu thd ljeh sir Holocen, dien hinh li de eit chin Dam Phi Tam Giang - Ciu Hai (Dai Tnrdng Sa) keo dii tir cira Viet lien quan tdi qui trinh phit trien ddng bing Quing Trj - Thira Thien Hue, de eit chin Dim Trudng Giang keo dii tir cira Dai tdi ciia Tam Hii lien quan tdi qui trinh phit trien ddng bing Hdi An - Tam Ky, v.v De eit chin gdm hai the he gdi tiep The he thu nhit li cic edn cit miu tring mudi tudi Holocen sdmgiira, eao trung binh 6-8m d phia trong, hien li noi quin eu ehinh eua eic cdng ddng din eu ven bien The he thu hai li eic cdn eit miu xam ving cao dd so, Uidi Holocen mugn, eao trung binh 20m, eao nhit tren 40m Dgc theo dim phi phia de cit chin, d nhilu noi xuit hien bii bii dang them duge sir dung lim dit d, eanh tie ndng nghiep hoac nudi thuy san De cit li hgp phin ciu tnic ehinh tao nen dim phi, nhung ddng thdi la vit cin lu vi giy ngap lut 229 Tiiu ban: Cdc Khoa hgc vi Trdi ddt ISBN: 978-604-913-016-8 ding bing ven bien He thdng de cit chin eao dd so chay dgc bd bien hang ehue kilomet di lam thay dii co ban hudng chiy cua sdng rdi qua cira dim phi trudc bien, lim cho thoat lii cham ding ke Trong dieu kien ngap lut ldn vi dii ngay, ddng lii cd the phi vo de cat chin d noi xung ylu dk tao cira mdi, giy thiet hai kinh te-xa hdi ning ne eho cdng ddng din eu ven bien Vdi ting dien tich mat nude 436,9 km^ he thdrig dim phi ven bien mien Tning Viet Narn rit da dang vl quy md (trong khoing 2,8 - 216 km') vi cd the duge phin biet thinh cip - rat nhd (dudi 10 km^), nhd (10-20 km^), trung binh (20-50 km^) vi ldn (tren 50km'), dd Idn nhit li Dim Phi Tam Giang - Ciu Hai vi thudc loai ldn cua the gidi Thudc tinh chung nhit cua lagun ven biin tren toin thi gidi li thudng cd hinh ding keo dai (elongate) dgc theo de cit chin, bilm ding thudc (equilateral) Neu liy ehi sd hinh bge la ty sl ^iira chilu dii vi chilu rgng dl dinh gii, thi trudng hgp I = I (thyc thy ding thudc) se rit hiem, khdng dinh gii duge die dilm ty nhien ciia thuy vyc ven bien kieu lagun Nhieu lagun ven biin eiia thi gidi eiing dugc md ti li ding thudc nhung chi sd I khoing - Do vay, cd thi coi lagun ding thudc I khoing - 1,5, bin ding thudc (semiequilateral) vdi khoing 1,6-2, va keo dii vdi I >2 Theo dd, nhiing lagun ven bien nhu Dim Ling Cd vi Dim Nai duge eoi li ding thude, cic Dim Trudng Gian^, An Khe, Nude Man, Tri vi Nude Nggt - bin ding thudc, cac Dim Phi Tam Giang - Ciu Hai, Cii Mdng, Thuy Trilu, Thj Nai vi Loan - keo dii Nhd sire chira thuy vyc mi dim phi ed vai trd dilu lii d mirc nhit djnh nhung edn tiiy thudc vio hinh ding va ning thoit lii qua cira Cie Dim Lin^ Cd, Dim Thj Nai hay Dim Nai ed hinh ding ding thude vi cira thoat lii tit, ngap lut ddng bing ven bien khdng ldn vi it xiy Sy biin ddng cira dudi cic dang khie (lip cira, thu hep, chuyen ddi vj tri, v.v.) deu co the sinh tai bien mdi trudng dja chit, lim thay ddi eo bin tinh chit cua vyc nude (tinh chat thuy hda, mdi trudng nude vi sinh thii thuy vyc, v.v.), thim chi bin ehat kieu loai vi thue day nhanh qui trinh phit trien d giai doan trudng thinh din tdi suy tin (ephemeral) va chet He thdng dim phi ven bien mien Trung Viet Nam di phit trien qua giai doan tre vi dang phat trien d giai doan trudng thinh Trong giai doan tre, hinh thii eic hgp phin ciu tnic din phit trien tdi can bang, nhung giai doan trudng thinh, chiing phit trien phin dj manh, lam gia tan^ tinh khdng dn djnh eiu tnic he, dd cd tinh khdng dn djnh cira Cira di trd thinh hgp phan ciu tnic quan trgng die biet quyet djnh sy tdn tai vi kieu loai lagun Dim An Khe (Quang Ngii) vi Dim Tri (Binh Djnh) li vi du dien hinh ve lagun dang phit trien d giai doan suy tan Do ddng bdi tich cit dgc bd hudng ddng nam-tiy bic phit trien manh ve miia he, cira bj djch chuyen tren doan bd dai 3-4 km, lire diu cira cdn ddng, md djnh ky theo miia, rdi sau gin nhu bj lip hin, lim eho vyc nude phia din trd thinh biu nude nggt vi lagun da suy tin Cira ddng, md tire thdi nhu cira Tu Hien, cira Hoi Duin d Dim Phi Tam Giang Ciu Hai sinh tai bien cip dien nhieu lin ljeh sir va giy hau qui ning ne Cira tan dan nhu cira Dim An Khe vi cira Dim Tra sinh tai bien trudng dien, cham nhung hiu qui vd eiing to ldn - lam thay ddi ban chit dja he, he sinh thii lagun ven bien, giim gia trj tai nguyen, thay ddi sinh ke, thim chi mit cic dieu kien sinh cu cira cdng ddng din cu ven bien Cd the dinh gia tinh chit dn djnh cira theo die diem eiu tnic cira (bing 2) Nam giira de cat chin (kieu 1), cira khdng dn djnh li tat yeu dudi dang lip, md, djch vi ehuyen ddi vj tri ddng bdi tieh eit dgc bd cd hudng vi cudng thay ddi theo miia Bdng Tinh dn dinh cira theo ddc diim cdu tnic Dam pha lien quan Tinh on dinh Khdng dn djnh dudi dang lap, Tam Giang - Cau Hai, Tnrdng Giang, An Khe md, dich va chuyen ddi vj tri Nam giira de cit vi Khdng In dinh doi cat phit Lang Cd, Nude Man Tri Kieu cau true I.Nam giiia de cit chin 230 Hgi nghi Khoa hgc kv niem 35 ndm Vien Khoa hgc vd Cong nghe Viet Nam - Hd Ngi 10 2010 bd di gdc trien tir mdt phia theo miia gay O, Nude Nggt, Thj Nai, O Loan, Nai bdi lip vi thu hep trie dien Nim giiia bd di gdc Cii Mdng On dinh Nim giira bd vjnh vi On dinh Thiiy Trieu de eit chin Dirn phi Tam Giang - Cau Hai cd hai cira, Thuin An vi Tu Hien Ke tir md cira Hda Duin lin diu vao nim 1404, cira Tu Hien khdng nhirng mit vai trd nhit mi cdn trd thinh cira phu, vi ei hai cira Tu Hien vi Hda Duan deu khdng dn djnh, bien ddng mang tinh chu ky vdi tin suit eao din Cua Tu Hien bien ddng ehu ky ngin vdi tin suit ting dan (Nguyen Hiru Cir, 1996) Tuong ty Dim Phi Tam Giang - Ciu Hai, Dim Truong Giang eiing ed hai cua Tam Hii vi An Hda cich qua mdt dang tich tu kieu tombolo dien hinh ndi vdi mii Bin Than (Miii An Hda) Cira Tam Hii nim giiia thdn va bj de dga bdi lip manh ve miia gid ddng bic cira An Hda d thdn xa Tam Hii dn djnh hon ddng bdi tich dgc bd ve miia gid ddng bie yeu va triing vao miia lii, ddng bdi tich dgc bd ve miia he phit trien manh vdi gid ddng nam nhung d ngoii cira vung An Hda Dim An Khe cd mdt cira, nim giira de eit chin nhung phit trien uu the tir mdt phia trii qua hai giai doan Vio giai doan Holocen giira, cira nim bd di gdc d phia nam vi doi eit Holocen giira d phia tiy bie, cira rdng vi siu Vio giai doan Holocen mudn vi hien dai, doi cit dgc bd tir phia ddng nam phit trien manh, djch cira ve phia tiy bie tdi km , ludng cira (entrance) nhd vi hep nhu ddng sdng, rdi nhanh chdng bj bdi lip Ket qui li dim An Khe dan nggt hoi vi ndng, din tdi suy tin Nim giira de cit vi bd di gdc (kieu 2), cua kieu phd bien d cie dim phi hinh thinh qui trinh san bing bd viing vjnh Holocen Tinh chit dn djnh cira tiiy thudc vio cudng ddng bdi tieh cit dgc bd phit trien theo miia vi lugng nude sdng dd vio dim phi tri trao ddi nude vdi bien Bien dgng cira phd bien dudi dang thu hep trie dien ve miia khd, md rdng trd lai ve miia mua, dien hinh li cira An Cu Ddng eua Dim Ling Cd, ed the de doa lap eiia ve miia khd vi phii xiy ke md hin (groin) ngin ddng bdi tich dgc bd, dien hinh li cira Dim Nude Man, Nude Nggt, Dam Nai Dam Tri vi O Loan eiing trii qua hai giai doan phit trien tuong ty Dam An Khe Trong Holocen sdm-giira, cira rdng vi dn djnh hon bdi sy phit trien ban ehe eiia doi eit ndi dio Trong giai doan Holocen mudn vi hien dai, doi eit phat trien manh ve phia tiy bic nhd ddng bdi tieh ddi dio ve miia he, din tdi djch chuyen cira ve phia tiy bic tdi 3-4 km vi lip ciia Hi Ra ciia Dim Tri O Dim Tri O dang d giai doan suy tin lugng nude sdng ve miia mua qui nhd khdng du giy hire xung md cira mdi nhu Dam O Loan (cira Tin Quy li cira ed tdn tai tir Holocen sdm-giira, Cira Phii Luong va cira An Hii tdn tai luin phien Holocen mudn vi hien dai Cira nim giira hai bd da gdc (kieu 3) nhu cira Dim Cii Mdng hay giira de cit chin vi bd vjnh (kieu 4) nhu eii'a Dim Thuy Trieu li cira cd trang thii dn djnh liu dai bdi ddng bdi tich dgc bd hiu nhu khdng ding ke Tie ddng eiia eon ngudi lim thay ddi din ciu tnic hinh thii dam phi ehu yeu li xay dyng eo sd ting (eiu, dudng, eing, hd chira luu vyc, v.v.), chiem eir khdng gian lim noi sinh eu, eanh tie, boat ddng du ljeh, thim ehi li thj hda Bii bdi thip dugc sir dung rdng rai vao nudi thuy sin, dien hinh li Dim phi Tam Giang - Ciu Hai, Trudng Giang, Thj Nai, Loan, v.v Bai bdi eao dugc sir dung phd bien lim dit canh tie, dit d, ngoai edn duge sir dung vao lim mudi nhu d Dim Nude Man, Nude Nggt, Thuy Trilu vi Dim Nai 231 Tiiu ban: Cdc Khoa hgc vi Trdi ddt ISBN: 978-604-913-016-8 KET LUAN (1) Dim phi ven bien mien Trung Viet Nam da dang vl hinh ding, ciu tnic yi quy md tir nhd tdi ldn, thim chi vio loai ldn ciia the gidi Hiu bet dim phi ven bien li bdn hdi luu eua nhilu sdng ldn nhd, cd vai trd dieu tiet lii nhit djnh, nhung ding thdi eiing li tic nhin gay ngap lut ding bing ven bien, giy nggt hoi vyc nude ve miia mua va xim nhip man siu theo sdng ve miia khd (2) Trong qui trinh phit trien dim phi qua cie giai doan, eic hgp phin cau tnic din thay dii kem theo tai biin ty nhien giy biu qui kinh te-xi hdi ning ne eho cie egng ddng din eu ven biin, dd cd biln ddng cira Tinh chit dn djnh cira biy thude vio kieu eiu tnic Nim giira de eit chin, cira tit ylu khdng In djnh; nim giira de eit va bd di gdc, tinh dn djnh cira tiiy thudc vio sy phit triln cua de eit; nim giiia bd di gdc hay bd vjnh kin, eua tit yeu on djnh TAI LIEU THAM KHAO Nguyen Huu Cir, 1995 He thdng dim phi ven bd mien Trung Viet Nam Cic cdng trinh nghien cim Dja chit vi Dja vit ly biln, trang 113 - 120 Nxb KH & KT, Hi Ndi Nguyen Hum Cir, 1996 Die diem dja chit he dim phi Tam Giang - Ciu Hai (Thira Thien Hue) Holocene va phire he triing Id chira chung Luin in PTS, Ha Ndi Nguyen Huu Cu, 1999 Tdng quan tinh hinh nghien cuu tii nguyen vi mdi trudng dim phi ven bd mien Trung Viet Nam Tii nguyen vi Mdi trudng bien, tip VI, trang 126 - 142 Nxb KH & KT, Hi Ndi Nguyen Hiiu Cir, 2000 Djnh hudng chien luge kien soit lii mien Trung Viet Nam Tai nguyen vi Mdi trudng bien, tip VII, trang 289 - 302 Nxb KH & KT, Hi Ndi Nguyen Hiru Cu vi nnk, 2002 Tic ddng eua eon ngudi tdi mdi trudng dja chit he dim phi Tam Giang - Ciu Hai Tii nguyen va Mdi trudng bien, tip IX, trang 103 120 Nxb KH&KT, Hi Ndi Nguyen Hiru Cu vi nnk, 2006 Nghien cim ddng thii mdi trudng dim phi ven bd mien Trung Viet Nam lam co sd lya chgn phuong in quin ly.Bio cio tdng ket Nhiem vy hgp tic Viet Nam-Italia theo Nghj djnh thu Nichols, M And Allen, G, 1981 Sedimentary processes in coastal lagoons Coastal lagoon research Unesco teehn pap mar sci N° 33, p 27-80 Phleger, F B., 1881 A review of some general features of coastal lagoons Coastal lagoon research Unesco teehn pap mar sci N° 33, p 7-14 Frignani, M., Nguyen Huu Cu et al 2003 Research on coastal lagoons of Central Vietnam as a guide to management Present knowledge and perspectives Teehn Rep N°86, CNNR, Italia 232 ... bien ty nhien lam co sd khoa bge de xuit irng xir tai bien d ven bien mien Trung Viet Nam TONG QUAN VE LAGUN VA DAM PHA VEN BIEN MIEN TRUNG VIET NAM Tir lagun ndi chung (lagoon, lagune, laguna,... va ven bd (coastal lagoon), ei vyc nude man vi nude nggt O Viet Nam, ed mat cic lagun xa bd quy md nhd nhu d quan dio Trudng Sa im tieu san hd tao thinh, ed lagun ven biin d miln Trung Viet Nam, ... Vien Khoa hgc vd Cong nghe Viet Nam - Hd Ngi 10 2010 CAU TRUC HINH THAI D A M PHA LIEN QUAN T I THIEN TAI 2.1 Kich thirac cabdn cdc ddm phd O ven bien mien Trung Viet Nam khoing vT 11° - 16° bie,