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GL 3 MASS MOVEMENT MONITORING ESSAY
Describe how sites of potentially hazardous mass movement can be
monitored. In your answer examine
why monitoring may not be effective. Illustrate your answer with
examples where possible.
(25)
Mass movements on a hillside o a !li"" !an #e monitoed die!tl$
and indie!tl$% Some o" the methods
&sed ae sho'n in the diaam #elo'%
Mass movements !an #e meas&ed die!tl$ &sin lase
s&ve$in% i*ed e"een!e +oints, s&!h as st&ds
!emented into sta#le o!-s, !an #e &sed to see i" the
distan!e #et'een them is !hanin #e!a&se the slo+e in
#et'een is movin% G.S (Glo#al .ositionin S$stem) !an also #e
&sed as satellites !an !a$ devi!es that
meas&e altit&de and +osition ve$ a!!&atel$%
/a!-s in the s&"a!e o" a slide !an #e meas&ed &sin
stain metes, 'hi!h !onsist o" 'ies "astened to
"i*ed +oints% The !hane in 'idth o" a !a!- !an #e !onstantl$
monitoed so that 'anin !an #e iven i"
&ne*+e!ted !hanes o!!&% Stain metes !an also #e +&t
do'n #oeholes to see i" the dee+e +ats o" a slo+e
ae movin% These !an #e a&tomati!all$ monitoed and
!om+&te anal$sed to see i" the movement is
daneo&s% Stain a&es ae &sed on the slo+es o"
vol!anoes, s&!h as 0e-la in I!eland, o a!oss -no'n
"a<s, s&!h as the San Andeas "a<% Vol!ani!
e&+tions and eath1&a-es !an tie landslides so the
in"omation !an #e &sed in seveal 'a$s%Geo+hones, 'hi!h
meas&e vi#ations, ae &sed in some +la!es% These assess slo'
movements in
o!-s and ssoil to see i" an$ movement is ta-in +la!e% In S'eden
and a+an the$ ae lin-ed to an a&tomati!
'anin s$stem 'hi!h tells tain dives ta-in o&tes a!oss the
&nsta#le aeas i" thee is an$ dane% That
means that the tains !an slo' do'n and sto+ i" a landslide is
dete!ted on the line ahead%
Monitoin needs to ta-e +la!e ove a lon +eiod o" time "o 'anin
sins to #e o#seved and
anal$sed% Thee needs to #e a "&ll &ndestandin o" the
eolo$ and 'ate movements in the slo+e i"
monitoin is oin to #e val&a#le%
Indie!t monitoin !an ta-e +la!e on the "a!tos 'hi!h !o&ld
!a&se a mass movement%
Man$ mass movements ae tieed #$ a ise in the 'ate !ontent o" the
slo+e, 'hi!h !an in!ease
+oe 'ate +ess&e and 'eiht% The ate A&thoities !an
meas&e the level o" o&nd'ate in a slo+e%4oeholes ae
monitoed so that the a&thoities ae a'ae o" the level o" the
'ate ta#le% I" the slo+e is ettin
sat&ated 'ith 'ate, then dains !an #e !leaed and 'ate
+&m+ed o&t
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The Meteooloi!al O""i!e has ain a&es in man$ sites so that
an in!ease in lo!al ain"all is -no'n
and 'anins !an #e iven%
.lannin de+atments o" lo!al a&thoities dema!ate land &se
aeas "o ho&sin and ind&st$ and need
to #e a'ae o" an$ +otential landsli+s% The 4itish Geoloi!al
S&ve$ ma-es ma+s 'hi!h in!l&de s&"a!e
de+osits as 'ell as solid o!- and thei eoloists !an identi"$ old
mass movement sites "om the lands!a+e
and the de+osits that the$ !ontain% The Mam To landslide nea
/astleton in e#$shie has ve$ h&mmo!-$
o&nd 'ith man$ dainae +i+es to emove the s&+l&s
'ate% The toe o" the landslide has ie&la o&nd
'hi!h !an #e +hotoa+hed e&lal$ to see i" thee ae an$ !hanes
in sha+e%
0a6ad ma+s ae made #$ enineein eoloists in aeas 'hi!h ae
v&lnea#le to mass movements% Inthe Al+s ma+s sho'in -no'n o!-
"alls ae +lished so that #&ildin does not ta-e +la!e in the
+ath o" a
landslide% Avalan!he monitoin allo's simila ha6ad ma+s to #e
made%
The Mam To hillside and othe stee+ slo+es in the e#$shie aea ae
'ell -no'n as havin the
+otential to slide #e!a&se o" thei !haa!teisti! eolo$ and
hih ain"all% The main oad ove Mam To 'as
!losed in 7899 #e!a&se its sa"et$ !o&ld not #e
&aanteed a"te it moved seio&sl$ "ollo'in a 'et 'inte% It
is
monitoed #$ s&ve$in and the net'o- o" "i*ed ma-es ae ma++ed
eve$ $ea% The ao's on the ma+
#elo' sho' ho' "a (lenth o" ao') and in 'hat die!tion that +at
o" the slo+e moved d&in the $ea%
A"te a#o&t 75 $eas o" monitoin it is !lea that the Mam To
landsli+ moves most a"te 'et 'intes% The
esea!hes ae #einnin to #e a#le to 'o- o&t the ma*im&m
amo&nt o" 'ate that the slo+e !an hold 'itho&t
movin sini"i!antl$ and that allo's them to +edi!t 'hen a
movement 'ill o!!&%
Monitoin ma$ not #e e""e!tive #e!a&se inte+etation o"
es<s is di""i!<% Some landslides o!!&
s&ddenl$, altho&h most stat movin ad&all$ so that i"
an$ one is a'ae o" the sins then 'anin !an #e
iven% The A#e"an !oal s+oil ti+ moved ad&all$ as moe 'aste
'as added and the men 'o-in thee 'ee
a'ae o" ho' m&!h settlin too- +la!e ea!h da$% 0o'eve the
dane o" the #&ild:&+ o" 'ate in the ti+ 'as
not e!onised so the ti+ "ailed massivel$ in 78;; and 73<
+eo+le died% It 'as not s$stemati!all$ monitoed at
all%
In some landslides the !iti!al "a!tos ma$ not #e e!onised% The
Vaiont am landslide in Ital$ 'as
monitoed as the esevoi 'as "illed 'ith 'ate on!e the dam had
#een !om+leted% 0o'eve the eoloi!al
'ea-ness in the hillsides a#ove the esevoi 'as not "&ll$
&ndestood so no one ealised ho' a+idl$ the slo+e
'o&ld "ail on!e it 'as sat&ated #$ 'ate at its
"oot%Sometimes a "a!to a!ts as a tie to stat a landslide, even
tho&h the slo+e is &nsta#le%
E*!e+tionall$ heav$ ain soa-s the o&nd s&ddenl$ and ma$
!a&se man$ landslides% Eath1&a-es ma$ sha-e
a slo+e so that it #eins to sli+%
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