Hgi Dja ly va TaJ nguyen M6i trirdng ThCra Thien Hue Hgi Dja 1^ Vigt Nam
Danh gia biln dpng lap phu cac tinh ven bien ddng bing song CLPU Long bang cong nghe vien tham - GIS, giai doan 2005 - 2010
Nguyen Hanh QuyBn', Pham Vict H6a', Nguyin Vil Giang', Tong ST Sun', Le Quang Toan', Nguyin Thj Quynh T r a n g ' Abstract
The extensively development of aquacullure della has been identified as major driver of mangrove forest cover change in Mekong river in recent decade, ll raised a practical demand on application of science and technology to monitor land use. land cover change. This study -ivas implemented focusing on the advantages of the integration of remote sensing technology and GIS for monitoring forest and land cover in 6 coast provinces in Mekong della consist of Ben Tre, Tra Vinh, Soc Trang, Bac Lieu. Ca Mau, Kien Clang Study results proved the preeminence of integration remote sensing technology and GIS in monitoring, management mangrove forest in the coast regions. All the result including interpreted land cover and land cover change was standardized and organized m a geodaiabase and digital maps, ll was also showed the time and labor efficiency, and cost benefits of proposed approach while maintaining the requested accuracy.
\. Dlyl V A N D E
Ddng bdng Sdng Ciru Long d u g c b i l l den nhu Id vua lua ciia ca nudc, la noi cung cap hem 5 0 % long san lugng gao lodn qudc hang nam. N h u n g ndm gan ddy, nganh nudi trdng thiiy sdn n h u nudi ldm, cua, ca tra, cd basa, cdng nghiep che bien thuc phdm d u g c md rgng dien tich va phat trien nhanh chdng d cac tinh ven bien ddng bang sdng Ciiu Long. Tuy nhien, chinh su phdt irien d at cua nganh nudi trdng Ihiiy sdn d u g c xem n h u nguyen nhan chinh anh hudng tdi s\i suy thoai va bien ddng dien tich rimg ngdp man d dia p h u o n g . Nhirng thay ddi manh me nay cdn cd the dnh hudng den he sinh thai tu nhien, din tinh da dgng sinh hgc, c u n g n h u cdc van de ve mdi trudng va cdnh quan. Dac biet su b i l n ddi cdnh quan sinh thai d khu vyc cdn ddn tdi nhiing tac dpng ti'ch liiy va kha nang chdng chju vdi dnh hudng ciia bien ddi khi hau loan cdu trong nhiing nam gan day. Muc lieu ciia nghien ciru lap Irung vao khd nang theo ddi b i l n d g n g ciia qua trinh sii dung dal vd phdn tich nhii'ng dnh hudng ciia nd den sy phdt trien ciia rirng ngap man ven bd.
2. PHU'CfNG P H A P T H y ' C H I £ N 2 . L D i i ' l i 9 u
Khu vyc nghien cii'u t h u c hi?n tren 6 tinh ven bien ddng bang sdng Ciiu Long bao gdm Ben Tre, Tra Vinh, Sdc Trang, B a c Lieu, Cd M a u , Kien Giang. T u lieu phan tich Id anh ve tinh SPOTS da phd, phan giai khdng gian 10m k i t h g p v d i mdt sd ngudn dii' lieu tham khao khac. Anh ve tinh d u g c thu thap trong 2 giai doan vao cac nam 2004-2005 va 2009-2010. Hau h i t cac anh d l u dugc thu vao mua khd tir thdng 12 d i n thang 3 nham ban c h e nhiing ldi nhdn dinh trong qud trinh phdn loai.
2.2. H 9 thong p h a n loaii
He thdng phan loai ldp phii mat dat da d u g c xdy d u n g n h u bdng dudi day (Bdng 1) d y a tren dac trung phdn bd t y nhien ciia ldp phu, kha nang chill tach thdng tin tren anh cimg vdi nhiing yeu cau theo quy dinh, quy pham qudn ly nha n u d c .
' Vi^n Cong nghe ^" Irv. ^i^n Khoa hgc vd Cong ngh§ Viel l^am DAO TAO DIA LY, PHU'ONG PHAP VA CONG NGHf NGHIEN ClTU DIA LY
Hgi Dja ly vd Tai nguyen Moi truong Thiia Thien Hui HQi Dja ly Vict Nam
2.3. Xu' ly anh ve tinh
Cdc anh ve tinh d hai thdi dilm dugc sir dyng trong nghien ciru ndy da dugc chgn sao cho c6 ngdy chup gdn nhau nhat, nhdm han che nhung bien dong ve miia sinh trudng va khac biet qua Idn ve phd phan xg ciia mdi ddi tuong d 2 ihdi diem. Tuy nhien van khd tranh khdi nhirng khdc biel nhdt dinh vl phan xa phd ciia cac doi lugng tren dnh d hai thdi diem cung nhu nhti'ng van de ve meo hinh hoc.
Chinh vi vay cong lac lien xii ly la mdt budc quan trpng da duoc thuc hien nham hieu chinh cac anh vl Cling mpl dilu kien tham chieu, nan chinh toa do cung nhu meo hinh hgc. Qua trinh ndn chinh anh dugc lhuc hien vdi sai s6 trung phuong dudi 0.2 pixel.
Cac anh sau khi dugc hieu chinh se dugc tiep bien va ghep lai vdi nhau vd cdt iheo ranh gidi nghien cuu Cdc anh nay sau do se dugc dua vao quy trinh xir ly bdn tu dpng, phan Idp theo bdi sd 10 ciia cac Idp cdn phan logi liiy theo su da dang va phirc tap ciia logi hinh Idp phii d khu vyc nghien ciiu. Cac phan Idp phu nay se duac danh gid va gop lai theo thdnh cac nhdm ldp khac nhau sii dung thdng lin bo trg tii Lac nguon lu heu bd tro nhu Google Earth, ban do sd dung dal, bao cao tlidng ke va thdng tin thuc dia. Qua trinh nay phdi dugc thuc hien nhdt quan giira cac canh anh irong qua trinh phan logi. Tilp theo, kicm dinh vien se phai Ihyc hien ddnh gia, hien chinh true quan de loai bo nhimg sai sd thd khdng dang co. Kct qua cudi ciing se dugc lgc thdng qua phep lpc "cua sd trugt" Kernel de "lam mugt" va cai thien chat Iugng topology ciia ket qua phan Ioai.
Bdng 1 Hi thongphdn logi lap phii a khu VMC nghien cuu
Nhdm
1. Nong nghiep
2 Ddt thi cu 3. Dat ngip nuoc
4. Mat nirdc
Loai ddt Ddt irdng lua Ddt thuy sdn Ddi Idm muoi Ddt trong cdy an qud
Ddt Irdng cdy khdc (vi du. rau, mdu) Ddt xdy dirng cdng trinh vd nhd a Ddt bai Irieu
Song, bien Ho
Kenh rach (kenh chinh)
Nhom
5. Dat rimg
6. Co
7. Nhom ddt khac Loai ddt Ddt rirng ngdp mdn Dal riing chdm Ddt rirng trdng Cdy ngdp man (cdy biti) Rirng ttf nhien (ricng thudng xanh)
Rirng tren niii da voi Ddt trong cd Bdi bien Dun cdl trdng cdy Dun cdl khdng trdng cdy __
2.4. Phan tich bicn dgng
Cong tac phan tich, danh gia bien dong truyen th6ng thudng dugc thuc hien tren dir lieu 'i.mg vector. Phuong phap nay cho thdy cd han chi rai ldn khi phai thao tac, xii ly va ddnh gia tren mgi ca sd du lieu idn, nhieu Idp d6i lugng, ddng thdi mat kha nhieu thdi gian. 6 day, chimg toi da dp dung phuang phap xir ly, danh gid bien dgng tren nin rasler nhdm giam dung lugng bd nhd, tiet kiem lh6i gian xu ly va rdi thuan ticn cho qud trinh danh gia, phan tich. Phuang phap nay cung giup Ioai bo nhirng nhan dinh sai trong qua trinh phan Ioai, dl dang chinh sira, nhat la khi phai ihao tac vdi ii?
thong phan loai phirc tap gom nhilu phan ldp, loai hinh Idp phii sit dyng ddt. Mdt md hinh dai sd rasler da duoc ap dung cho 2 kll qua giai doan, phan Ioai ldp phii sii dyng dat nam 2005 va 2010 da hoan
Hgi i}\a ly va TAi nguyen Moi truong Thua Thicn Hue Hgi Dja ly Vict Nam
thdnh d budc irudc. Kel qua thu dugc la 1 file raster tich hgp bao glm ca thdng lin vl hicn trgng va bien dgng giira hai ihdi diem nghien curu.
3. KET QUA VA THAO LUAN
De lai tap trung vdo ddnh gia bicn dgng sii dung dal va rirng ngdp man cdc tinh ven biln dong bang sdng Ciru Long, vi vay dii lieu dnh ve tinh SPOTS dugc lhu thdp tap trung vao cac tinh ven biln tir Ben Tre den Kien Giang. Tuy nhicn, do dac thii nhieu may mii d khu vuc nghien ciru, anh v? tinh ndm 2010 da khdng the thu dugc d viing bd thugc linh Trd Vinh va mgt phan nhd Ihupc Bac Lieu, Kien Giang. Ben canh do, dnh thu dugc cOng bao gdm mpt phan dien tich cdc tinh lan can, do vay kit qua mpl phdn ldp phii d cac tinh Vmh Long va Hau Giang cung dugc giai doan.
De cd the nhgn dien va phdn tich bien dpng giira hai ihdi diem mdt cdch chinh xdc, chi lill, trong bao cdo nay chiing tdi chi lien hanh linh loan, ddnh gid bien dong tai nhirng khu vuc cd dnh ve tinh bao phii trgn vgn cd 2 Ihdi diem, cy thi la linh Ca Mau, nai lap trung phan ldn dien lich rirng ngap mgn ciia viing ddng bdng sdng Ciru Long.
3.L Danh gia thuc trang ldp phu tai cac tinh
Tir ket qua giai dodn ldp phii nam 200S - 2010 cho viing ven bien ddng bdng sdng Ciiu Long, chiing ta cd the thdy hogt ddng ndng nghiep vdn la hudng phal trien chinh ciia khu vyc nghien ciiu, mdc dll mdi tinh lai cd hudng phal trien rieng nhu trdng lua, nuoi trdng thuy san, trdng cay dn qua hodc cdy hdng nam. Ddt rimg ngap man phan bd chii yeu d dai ven bien va bdn dao Ca Mau, trong khi rirng tram, mdt logi rirng ddc huu d khu vyc, phdn bd chii yeu tren dat phen va dat than bim.
Tgi cdc tinh ven bien phi'a Ddng Bac nhu Ben Tre, Tra Vinh, Sdc Trdng, rirng ngap man phdt tnen ty nhien d cac bai trieu sat vdi khu vyc nudi Irdng ihiiy sdn ven bicn. Sdu Irong ddt lien Id khu vyc irdng liia, trdng cdy an qua vd cay hang nam. Trong nhirng nam 2004-2005, cac tinh nay cd dien lich trong lua chiem khodng 43-46 % dien tich ca tinh; dien tich trdng cdy dn qud chiem 29-3S%) d Ben Tre va Vmh Long, 13-14% d Sdc Trang va Tra Vinh; dien ti'ch nudi trdng thtiy san d miic trung binh, khodng 13-18%o dien lich cd tinh ngoai trir VTnh Long
Cac tinh phia Ddng Nam giap bien nhu Bac Lieu, Cd Mau cd dien tich nudi trdng thuy san kha ldn, chilm 44-47% dien tich cua tinh trong ndm 2005 vd 48-51 % trong ndm 2009, khu vyc trdng liia cd dign tich nhd hon, 10%i d Ca Mau va 27%i d Bac Lieu, phan bo chii yeu d nhirng viing dal cao. Ben cgnh do, Ca Mau cung la tinh cd dien tich rimg ngap man che phu cao nhat dong bang, chiem 15%
dign tich ca tinh trong ndm 2004-2005, ly Ie nay gidm xudng cdn 10%i trong nam 2009-2010. Mpt irong nhirng diem can chii y trong khu vuc nay la mgi dg nudi trdng thuy san dugc giii d ly le 4/6 hogc 3/7 cho "rirng ngap man/dal thiiy sdn" de bao ve rirng ngap mgn, va trdng phyc hdi theo djnh ky.
Nam d phia Tay dong bang sdng Cira Long, Kien Giang cd viing canh tac liia khd ldn, chiem khoang 36% dien tich loan tinh. Noi day vdn dugc biet den nhu khu vuc cd dien tich rirng trdm rgng ldn vdi Vudn Qudc gia U Minh Thugng, dien tich rimg tram chiem khodng 12 % dign tich ca linh nam 2004-2005.
Danh gia chung vl biln dgng trong nhitng tinh nay giira 2 giai doan 2004-2005 va 2009-2010 cho thdy loai co su gidm nhe vl dien tich liia ciia Bac Lieu, Sdc Trang, Hdu Giang, Kien Giang (khodng 2%), Id nhirng nai cd the coi nhu dugc chuyen ddi sang Irdng cay hang nam khac.
DAO TAO D|A LY, PHlTONG PHAP VA CONG NGHE NGI [ICN CU^J DjA LY
Hgi Dja ly va Tai nguyen Moi trudng Thiia Thicn Hue Hgi Dja ly Vigl jNaiB
•^ * - * BAN 0 0 HIEN TRANG lOP PHU 1> OONG BANG SONG CU U LONG NAM 2004 2005
O O N G BANG S O N G C U U L O N G N A M 2009 2010
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Hinh 1. Cdc bdn do kit qua lap phu vd biin ddng Idp phii thdnh tap tu dnh vi linh SPOT khu virc cdc tinh ven bien ddng bdng song Ciiu Long, giai dogn 2005-2010.
Rimg ngap man d Ca Mau la loai hinh Idp phii cd tdc dp biln dgng nhanh nhdt. Trong vnim 5 nam, dicn tich rimg gidm gan S% tren loan tinh. Phan Idn dicn tich rimg nay bj thay ddi do chuyen dm myc dich Ihanh ddt nudi trong thiiy san (dien tich nudi thuy san lang hon 4% trong giai doan nay).
Thdng ke ciing chi ra rang co vai noi chuyen ddi tir nudi Irdng thiiy san sang cay byi ngap man, va lu cdy bui ngap man sang rirng ngap man Ngodi ra, rirng ngap man ma chii ylu la mam va dude cdn phat trien md rdng ra mdt phan dicn lich bai trieu dgc bd bicn Bgc Lieu, Sdc Trdng vd Kien Giang.
Hot nghi Khoa hoc Dia ly Todn qudc ldn thu 6: Thdnh phd Hue. 9/20 C
Hgi Dja ly va Tai nguyen M5i t r u o n g Thii-a Thicn H u i Hgi Dia ly Vicl Nam
3.2. Ddnh gia bien dgng Idp phii - Bien ddng dien tich rirng ngap man:
Rirng ngap man d ddng bang sdng Ciiu Long chu yeu tap trung d tinh Ca Mau. Trong ndm 2004-2005, rimg ngap man d Ca Mau chiem 77%i dien tich rirng ngdp man loan khu vuc nghien ciru, nhung den giai doan 2009-2010, ly le nay chi con Igi 72,3%. Bdn dd Idp phu d hai thdi dilm cho Ihay rimg nggp man d Ca mau chu yeu tap trung d huyen Nggc Hien, Nam Cdn, Dam Doi vd Phii Tdn.
Bdng 2. Dien tich biin ddng rimg ngdp man lai 4 huy^n thupc tinh Cd Mau
Bi^n dgng rirng ngap m^n Rimg ngap m|in chuyen doi tlianh dal thuy san nam 2009
Nhirng loai hinh Ichac thanh rirng ngap min
Rimg ngiip man khong bien dong Tong dien tich rimg ngap man nam 2004 Ty IS bi^n dong
Di^n tich 1 Nggc Hicn
lla
9387.05 3143.66 23518.83 36270-83
%
25.88 8.67 64.84 100 17.21
Nam Can Ha
5087.04 1852 43 8998.55 16030.95
%
31.73 11.56 56.13 100 20.18
0 a m Do'i Ha
2550.17 545.91 5123.58 8668.06
%
29.42 6.30 59.11 100 23.12
Phil Tan Ha
1248.85 715.28 2735.43 4573.26
%
27.31 15.64 5981
locJ
11.67 Bang bien ddng nay chi de cap den dicn tich rirng ngdp mgn bj mdt do chuyen sang muc dich nuoi trdng thiiy san. Do dac thii phan bo trong lhuc te, rirng ngdp man d day nam xen ke vdi dal nudi trdng thuy sdn, do do cd mgt sd khu vyc khd ldn rirng ngdp man bi chgt, lia va suy thodi chi cdn Igi nhu cdc byi cay ngdp man. Ban dd Idp phii d tren cho thay, rirng ngap man bj mat, chii yeu tap trung d ddi gan bd, giap vdi rirng phdng hd, rd rang nhdt la d cac huyen Dam Doi va Nam Can. Ngodi ra, dieu ddng chu y la tren dia ban huyen Nggc Hicn, dicn tich rimg ngdp man bi mat lai thudc dja phan quan ly cOa vudn qudc gia. Xdi Id bd bien ciing dugc xdc dinh Id mgt nguyen nhan lam gidm dign tich rirng nggp man d Ca Mau. Kel qua ddnh gia, so sdnh cung cho thdy dien tich rimg ngdp man d viing bai trieu lhi van phdt trien md rgng do chua cd trir Iugng va dugc bdo ve nghiem ngat.
Bien dpng dien tich nuoi trdng thity sdn:
Dien lieh dat thuy sdn lang len d cac tinh Bac Lieu, Cd Mau va Kien Giang, ddc biet ly le ddt nuoi trdng Ihiiy sdn tang nhanh tir 44%) nam 2004-2005 din 48%i dien tich ca tinh vao nam 2009 tai Ca Mau, va lgi Bgc Lieu Id tir 47%» den 50,8% trong vong S nam
Thong ke vl bien dgng sii dung dat d Cd Mau ciing cho thay nganh nuoi irong thuy san phal trien nhanh chdng dNam Cdn, Nggc Hien, Phii Tdn, Dam Dai va thdnh phd Cd Mau. Bicn ddng xay ra nhieu nhat d huygn Ndm Cdn va Dam Dai, nai ma dat nudi trdng thiiy sdn phdn Idn dugc chuyen ddi tii rimg ngdp man.
Bien dpng rimg trdm vd rimg trdng:
Riing tram cd d Hdu Giang, Sdc Trdng, Cd Mau va Kien Giang nhung chii yeu tap trung d Kicn Giang, Ca Mau nai cd 2 rirng qudc gia U Minh Thugng va U Minh Hg. Tinh todn thdng ke cho thdy, long dign tich riing tram cua mdi tinh giam nhe lir nam 200S den 2010. Tuy vdy, d Kien Giang, dien tich rimg tram trdng tang len kha nhanh, phdn nhilu tir dat cd trong, tir 8,1% din 9,3% dien tich ca tinh.
DAO TAO DIA l.Y. PHUONG PI lAP VA CONG NGHE NGHIEN CUU DIA LY
Hoi Dja ly vd Tai nguyen Mfli truong Thiia Thi£n Hue Hoi Dja ly Viet N.im
Biin ddng diin tich liia:
Ket qua nghien cuu cho thay, ldng dien lich trdng lua ciia tat ca cac tinh dlu giam khodng 2-)%
so vdi nam 2005 chii ylu do chuyen sang dat trdng cdy dn qud hogc cdy hang nam khac. Do thicit dir lieu anh cua ndm 2010 d vdi linh ncn nghien ciiu khdng Ihl tiln hanh so sdnh, ddnh gia mdt each loan dien ly Ie tang hay giam ciia dat trdng liia trong loan khu vuc nghien cuu.
KET LUAN
Danh gia, phdn tich bicn ddng sir dyng dat ciia khu vuc ven bien cua ddng bang sdng Cuu Lono dugc thyc hien thanh cdng dua tren kel qud phan logi anh ve linh SPOTS. Ddnh gid da thi hicn sir phan bo ciia cac loai dal phii khac nhau vd hudng chuyen ddi tir cac he sinh thai ly nhicn thanh he smh thai nhdn tdc, vi dy bicn dpng rd ret nhat Id lir rirng ngap man chuyen sang ddt nudi trdng thiiy san.
Ben canh sy gidm nhanh ciia dien tich rirng ngap man, khu vyc rirng tram lai dugc duy tri, bdo vc \6i dien tich rirng trong tang nhe d Ca Mau va Kien Giang. Kel qua phan tich tren anh ve tinh cung cho thdy xoi Id bd bien dien ra manh d bd phia Ddng tinh Cd Mau trong khi do cung cd mgt phan dicn ndi bai boi gia tang d bd Tdy.
Mat dp ciia canh tdc nudi Irdng Ihiiy san d Ca Mau dan xen vdi rirng ngap man de tgo ncn su nham Ian trong qud trinh phan loai. Ben cgnh do, phuang thirc khai thdc rirng ngap man theo chu ky (5-7 nam) eting gay trd ngai cho qud trinh nhan dien bien dgng rirng ngap man vdi ddt nuoi irdng thiiy sdn Ircn anh.
Qua trinh phan loai cung gap trd nggi do dnh d mgt vdi khu vuc nhu Sdc Trang, Ca Mau va VTnh Long bj mdy che phu, ddng thdi khdng thu dugc dii dir lieu anh can thiet d Biin Tre, Tra Vinh cung gdy trd nggi cho viec ddi sanh ket qua giira cac thai diem.
Vice td chuc phan loai tren mdt khu vyc rdng Idn co the tgo ra su khong thdng nhdt khi phan Ioai va giam do chinh xac ciia kel qua. Mdi chuyen gia xir ly anh lai cd kien thiic ban dja cung nhu kinh nghiem giai doan khac nhau d mdi khu vyc nghien ciiu. Vl vay cdn kiem tra cheo ve kct qua phau loai giii'a cdc nhdm hieu chinh va tao ra ket qua cudi cimg thdng nhat, chinh xac.
Ti I LIEU THAM KIIAO
I. Spate Technology Institute, lUCN "Land use/land cover change assessment in Mekong river deltafi-om 2004-2005 to 2009-2010", Technical report, 2011.
lldi nghi Khoa hoc Dia ly Todn qudc ldn thu 6; Thdnh phd Hue. 9/20!
