TAI BIN B BIN XI L B BIN V BO NHIT I

NI DUNG

I. Gii thiu v tai bin b bin

II. Cc qu trnh b bin

III. Xi l b bin

IV. Tai bin b bin v cc cng trnh kin trc

V. Hot ng ca con ngi v xi l b bin

VI. Bo nhit i

VII.Nhn thc v iu chnh nhng tai bin b bin

I. GII THIU V TAI BIN B BIN

Vng ven bin th a dng v a hnh, kh hu v

thm thc vt, ni chung n l mi trng nng

ng.

Cc qu trnh hi t (converge) lc a v i

dng dc theo b bin to ra cc cnh quan c

trng c kh nng thay i nhanh chng.

Cc qu trnh tai bin b bin c tc ng ng k,

bi v c nhiu khu dn c nm gn b bin.

NHNG TAI BIN B BIN NGHIM TRNG

Dng rip

(Rip currents)

Sng thn (Tsunamis)

Xi l b bin (Coastal erosion)

Bo nhit i (Tropical cyclone)

01 02

03 04

II. CC QU TRNH B BIN

Gi thi trn mt nc ma st dc theo ranh gii gia

nc v khng kh. V khng kh di chuyn nhanh hn nc

chuyn ha mt phn nng lng ca n vo nc

SNG

Kch thc sng hnh thnh ph thuc

Vn tc gi Khong thi gian

gi thi

Khong cch gi thi ngang qua mt nc

SNG (wave) 1

CC THNG S QUAN TRNG

Chiu cao song - H

(wave height)

Chiu dai song - L

(wave lenght)

Chu ki song - T

(wave period)

Cc nhm sng c to ra bi nhng cn bo xa

ngoi khi c gi l sng lng (swell).

Vi iu kin vng nc su, c phng trnh

d on chiu cao, chu k v vn tc sng

c tnh kh nng xi mn b bin bi sng

Sng s gii phng nng lng khi chng n b

bin. Nng lng sng gn t l thun vi bnh

phng ca chiu cao sng.

Nhng con sng gn b, ngay bn ngoi i sng nho (surf zone), t mt dc khng n nh

sng v ra v gii phng nng lng trn b bin.

S hi t v phn k ca nng lng sng

S khc x (refraction) hoc un cong (bending) ca mt sng

php tuyn sng hi t mm v phn k vnh.

S gii phng nng lng sng nhiu hn vo nhng khu vc nh ra

xi mn do sng c xu hng lm bin dng ng b bin.

Song v b (plunging

breaker): l nguyn nhn

ca nhiu hin tng xi

l b bin.

Sng tran b

(spilling breaker): nh

nhng hn v thun li

cho s lng ng ct trn

bin.

Hnh thi v cc tin trnh b bin 2

Bi bin (beach): l dng a hnh bao gm cc vt liu khng kt

dnh vi nhau nh ct, si c tch ly qua cc hot ng ca sng.

S vn chuyn ct 3

Vn chuyn trm tch ven b

(longshore sediment transport)

Dng chy ven b

(longshore current):

dng nc chy song

song vi b bin

trong i sng nho

hnh thnh bi nhng

con sng n p vo

b mt gc

Khi hng lot con sng ln ti v

v ra trn bi bin, nc c xu

hng xp chng, tp trung

nhng khu vc hp dng rip

Dng rip khng phi l thy triu

v khng ko con ngi xung

nc, nhng chng c th ko

con ngi ra xa b.

Dng rip (rip current) 4

Dng rip (rip current) 4

L mi nguy him nghim trng trn b bin i vi

ngi bi, vi vn tc > 6 km/gi

Tng i hp (t vi m - vi chc m), chng tiu

tan bn ngoi i sng nho, trong phm vi hng

chc n hng trm mt ngoi khi.

L khu vc tng i yn tnh trong i sng nho.

Nc trong cc dng ny thng sm mu hn do cha

ng trm tch l lng.

III. XI L B BIN (Coastal erosion):

L kt qu ca s gia tng

mc nc bin ton cu

v pht trin khng thch

hp vng ven bin

L mt qu trnh lin tc,

c th d on nhiu hn

so vi cc tai bin t

nhin khc

Click to add Title 1 Lng trm tch bin: 1

ven b (littoral cell):

bao gm ton b chu trnh

vn chuyn trm tch n

b bin (bi sng & xi l),

vn chuyn dc b, v cui

cng l s mt mt trm

tch t mi trng ven b

Lng trm tch bin (beach budget): mi khu vc c mt lng trm

tch nht nh, bao gm qu trnh vn chuyn n v ly i hng nm.

Nu lng ly i > vn chuyn n b bin xi l

Click to add Title 2 Cc yu t xi mn 2

Bo nhit

i v

nhng cn

bo d di,

gi l gi

ng Bc

(Notheaster)

Xy p

ngn ct

bi bin thiu thn

trm tch v

b xi l.

1 2 3 4

S can

thip ca

con ngi

vo cc

qu trnh t

nhin ca

b bin

S dng ln

ca mc

nc bin

Click to add Title 1 Xi mn vch ng ven bin 3

Nguyn nhn

Sng: loi b lp ph ct

lm chn vch l ra

ng thot nc thi trc

tip ra vch ng bin.

Ti cc bi c trn nh

vch

Pht trin khng ph hp

ca con ngi

Tc xi l b bin c th xc nh bng cch s dng vin thm

S rt lui

c

qun l

S n

nh mm

S n

nh cng

cng trnh

kin trc bo

v b bin

khi sng

bin (seawalls)

k m han (groins)

chn song (breakwaters)

cu tu (jetties) www.PowerPointDep.net

IV. TAI BIN B BIN V CNG TRNH KIN TRC:

b sung thm ct

vo bi bin

(nui dng bi bin)

sng cng vi xi l b bin

kt hp n nh mm & cng

1) S n nh cng:

a. bin (Seawalls):

-bng b tng, tng, g, hay vt

liu khc.

-xy song song vi b bin

lm chm qu trnh xi mn.

-nh hng: sng di li mnh m,

tng xi mn v Sb bin thu hp vi

lng ct t hn, gim thm m

chn sng Galveston (Texas) loi b

tm quan st ven bin v lm thu hp bi bin.

vic thit k v xy dng bin phi c iu chnh cn thn cho nhng v tr c trng.

b. K m hn (Groins)

-l nhng cng trnh tuyn tnh c t vung gc vi b bin, thng

t hp li thnh nhm, gi l vng k m hn

-mi k m hn c t on b ni c ct ang x dch

c. chn sng (breakwaters) v Cu tu (jetties):

-c thit k chn sng v to ra mt khu vc

c bo v, hoc bn cng, cho tu thuyn neo

-C th gn lin vi b bin hay tch bit

-Thng c xy dng thnh tng cp ca

sng hay li vo mt m ph, ca bin hoc vnh.

-c thit k n nh knh v bo v chng

khi cc con sng ln.

S minh ha cc tc ng ca chn sng v cu

tu trn m hnh cc b v s lng ng v xi mn.

2) S n nh mm:

Nui dng bi bin (Beach nourishmen):

-t ct nhn to xy dng mt lng trm tch bin chc chn

-u im: thm m tt hn nhiu cng trnh k thut, cung cp mt

bi bin vui chi gii tr v bo v b bin khi b xi mn.

B bin Miami trc v sau khi nui dng

V. HOT NG CA CON NGI V XI L B BIN:

Click to add Title 1 B bin i Ty Dng: 1

c trng bi cc o chn (barrier

island) - nhng o di, hp tch bit

khi t lin bi mt vng nc.

Nhiu o chn b bin i t

nhiu bi s dng v li ch ca con

ngi.

Vng Outer Banks Bc Carolina nh mt di

ruy bng trng mng ca ct. Cc o chn

tch ra khi t lin bi Pamlico Sound

Pht trin

th bng

vic xy

dng cu

tu lm

tng xi l

b bin.

Click to add Title 1 B bin vng vnh: 2

Xi l b bin l mt vn nghim trng dc theo Vnh Mexico.

Cc cng trnh k thut, st ln do suy thoi ngun nc ngm, xy

dng p trn sng tng tc xi mn

Click to add Title 1 Ng i H: 3

Xi mn din ra nh k dc theo

b ca Ng i H

Ma ln ko di mc nc h

tng cao bi bin hp dn

sng bo gy xi l b bin ng

k

nhiu ta nh, ng, tng chn,

v cc cng trnh khc b ph hy

Ngi nh ny b ph hy t trn xi l b bin

dc theo bin h Michigan

VI. BO NHIT I:

Bo nhit i

Typhoons

(Thi Bnh Dng)

Hurricanes

(i Ty Dng)

Ly i hng

trm ngn

mng sng

S hnh thnh v tin trin ca bo nhit i:

Bo nhit i l mt s bin i

ca xoy thun nhit i (tropical

cyclone) - mt chui cc cn ging

(thunderstorm) ln, phc tp xoay

quanh mt vng p thp (low

pressure), hnh thnh trn vng

nc bin nhit i m p

Hu ht c hnh thnh trong mt vnh ai gia 80 B v 150 N, ni

m nhit b mt nc m > 27oC.

Khi khng kh m i ln, s ngng t (ma) din ra khi nhit

n c gii phng, lm m khng kh v lm cho n nh

hn. Khi khng kh nh i ln, nhiu nng lng t nc m

c thu vo v cn bo c th tng kch thc, sc mnh

v cng .

Khi sc gi t 63km/h bo nhit i v c t tn

Khi t 119 km/h hurricane

Chiu quay ca bo: ngc chiu kim ng h bn cu Bc

v thun chiu kim ng h Nam bn cu.

Mt bo (wall): vng p sut

thp tng i yn bnh nm

trung tm cn bo.

Thnh mt bo (eye wall):

vng st mt bo, ni gi

xoy mnh nht

Di ma (rainband): to ra

khi khng kh m xoay quanh

trong cn bo

S hnh thnh v tin trin ca bo nhit i:

Nng lng t nc bin m c bin i thnh

bo, n c th c ng knh 600 km.

Cu trc ca bo:

Bo

nhit

i

c

phn

loi

theo

kch

thc

v

cng

. p thp nhit i c th pht trin thnh bo c theo di cht ch t

v tinh v bng cc phi c c thit k c bit i xuyn qua bo.

D on chnh xc v tr v thi gian cn bo c th tn cng t

lin gim thiu thit hi v ngi v trnh s tn khng cn thit

Sng cn (storm surge)

L s gia tng mc nc bin do

gi t cc cn bo y nc v

pha b bin.

Di chuyn su vo t lin lm

ngp nh ca, xi l b bin

nghim trng.

Sng cn to ra bi cn bo Gloria vo

27/9/1985, New Jersey

Mi nguy him do bo gy ra

Gi ln: tc mi, thi bay cy c th v ng dy in, tn ph

cc cng trnh.

Tuy nhin, gy tn tht v ngi v ti sn nhiu nht l:

l lt (do ma d di v sng bin trn vo t lin)

sng cn.

Ngn hi ng mi t Florida trc v sau cn bo Andrew, 25/8/1992.

Hu ht mi ngi iu nhn thc c s xi l, nhng bit rt t

v tn sut xy ra, mc nguy him v kh nng d on ca n.

VI. NHN THC V IU CHNH NHNG TAI BIN B BIN:

1) Nhn thc v xi l b bin:

2) iu chnh cc tai bin b bin:

Bo nhit i

tng cng cu trc bo v

gia c t

quy hoch s dng t tt hn

s tn v cnh bo

phc hi vng t ngp nc Nh chng bo Florida, c xy dng vi cc khi vng chc

Xi l b bin

Nui dng b bin

Cng c ng b bin bng k m hn, bin.

Thay i cch s dng t (khng xy dng trong khu vc nguy

him hoc dch chuyn nhng ta nh b e da).

1

S xi l b bin l mt qu trnh t nhin hn l mt tai bin t nhin, xi l xy ra khi con ngi xy dng nhng cng trnh ven bin.

2 Bt k s xy dng ven bin no cng u gy ra s thay i.

3

n nh vng ven bin thng qua cc cng trnh k thut bo v ti sn ca vi ngi trong khi c cng ng th phi chu mt mt rt ln.

4

Cc cng trnh k thut c thit k bo v b bin i khi li c tc dng ngc li

5

Sau khi xy dng, cc cng trnh k thut to ra mt xu hng trong pht trin ven bin, kh c th phc hi, vic sa cha cc cu trc cn chi ph rt ln.

5 nguyn tc nn bit

1

2

3

Mi trng ven bin (coastal environment) l mt

trong nhng khu vc nng ng nht trn Tri t

Sng bin c to ra bi nhng cn bo ngoi khi

v truyn nng lng n b bin. Nhng con sng

n p vo bi bin mt gc dn n s vn

chuyn dc b ca trm tch bin.

Dng rip l mt mi nguy him nghim trng i vi

ngi bi. Chng c th c nhn ra v trnh xa

4 Xi l b bin l mt vn nghim trng gy ra bi

vic xy p sng, bo ln, v s gia tng mc nc

bin ton cu.

TM TT

5

6

7

S can thip ca con ngi vo cc tin trnh b

bin t nhin i khi thnh cng, nhng trong nhiu

trng hp gy xi l b bin ng k.

Tai bin b bin thm khc nht l bo nhit i - cn

bo d di mang theo gi ln, sng cn v l sng.

Nhng iu chnh i vi bo nhit i thng thng

l cc cu trc bo v, quy hoch s dng t tt

hn, s tn v cnh bo.

8 Qun l xi l b bin: lp k hoch s dng t cn

thn, cho php s xy dng trn c s d on tc

xi l b bin.

TM TT