Thuy trieu vd ddng trieu ven bien
Khu v\xc bien ven bd \aing cira song Hdng ed che dp nhat tndu deu voi bidn
va mdt chan tri^u (nude ddng). Trung binh trong mdt thang cd hai ky nude Idn vdi dao dong muc nude tir 2- 3,5 m. Vao thdi ky nude kem, tinh chdt nhat tridu giam di r5 ret, cdn tinh cha't ban nhat tri6u tang len, trong ngay xual hien hai dinh tndu, thdi ky nay cdn cd ten gpi la nude "sinh con"
Tai cira Ba Lat thdi di^m xuat hien nude Idn thudng sdm han thdi didm xual hi^n nude lan tai Hdn Dau la khoang 30 phiit va thdi didm xuat hien nude ddng cham hon 30 phiit.
Khac vdi che dp dao dpng muc nude, ddng tridu d viing nghidn cun co che dp nhat tri^u khdng deu. Ddng trieu cd chu ky ngay chiem uu the, chu ky 1/2 ngay nhd han va chu ky 1/4 ngay khong dang kei. Cung nhu dao dpng muc nude, ddng tndu Idn trong nam xuat hien vao cac thang VI, VII, VIII, XII, I. Van tdc Idn nhat ciia ddng tridu dat 60- 70 cm/s, true Idn ciia Flip tridu d khu vuc bidn ven bd Thai Binh- Nam Dinh cd hudng song song vdi dudng bd. tiire la hudng NE- SW. Tdc dp ddng trieu tai cira Ba Lat cd gia tri trung binh bdng 30- 40 cm/s. Ddng trieu dat gia tn Idn nha't khi muc nude trieu gan vdi muc nude trung binh, con khi muc nude cao hay thap nha't thi van tdc ddng trieu lai nhd nhat. Theo nhieu tac gia thi che do dao dong muc nude va ddng tndu cd vai trd dang kd trong vide hinh thanh cac bai tndu va iach trieu viing cira song.
Dong chdy ven bd.
Ddng chay ven bd thudng co van tdc kha Idn, dd la ke't qua tdng hgp ciia tat
ca eac yeu td dpng lire ca ban vimg ven bd: sdng, ddng chay gid, dong chay mat dp, ddng trieu. Phan tfch chd dp ddng chay ven bd bidn Thai Binh- Nam Dinh cho tha'y, van tdc ddng ven chiu anh hudng rat Idn ciia dia hinh vimg bd, su thay d6i dp ddc bai bidn va hinh dang dudng bd. Tai vimg bidn thoang, dp ddc bai Idn. gia tn eiia ddng ven Idn han nhieu so vdi cac khu vuc gdn cira sdng, cac gia tri cue tn ciia van tdc thudng xdy ra vao thdi didm gdn dinh tridu, Gia tri Idn nhat eiia van tdc khoang 40- 70 cm/s.
Ch^ dd sdng gid 6 vimg bidn giap chau thd sdng Hdng thay ddi theo miia. Vao miia d6ng, thang XII- III, hudng sdng thinh hanh ngoai khoi la ddng bdc (61%), ddng (15%) va ven bd la dong (34%), dong bdc (13%), dong nam (18%). Dp cao sdng trung binh ngoai khai la 1,2 m va ven bd la 0,5- 0,6 m. Dp cao sdng Idn nhat ngoai khoi la 6,6 m va ven bd la 2-3 m.
Vao miia he, thang V-IX, cac hudng sdng thinh hanh ngoai khai la nam, tay nam va ddng vdi tdn suat 40- 75 %, trong dd sdng hudng nam chiem tdn suat uu the: la 37 %. Ngugc lai, viing ven bd sdng cd hudng chinh la dong nam vdi tdn suat trung blng la 24 %. Dp cao sdng trung binh ngoai khoi bdng 1,2-1,4 m va ven bd la 0,6- 0,8 m. Dp cao sdng Idn nhat ngoai khoi la 6-8 m va ven bd la 5-6 m. Sdng cd dp cao Idn ddu xuat hien trong trudng hop cd ap thap nhiet ddi hay bao dd bp. Khi co bao, sdng Idn d vimg ven bd co hudng dong, ddng bac, dong nam.
Vao miia chuydn tidp, trong cac thang IV, VI hudng sdng chii dao ngoai khoi chuydn ddn tir dong bdc sang nam va ven bd tir dong sang dong nam. Vao cac thang X, XI sdng cd hudng bien ddi ngugc lai. sdng thinh hanh ngoai khai la dong bac va ven bd la dong. Cudng dp sdng trong cac miia chuydin tie'p bi giam di dang kd.