Hazardmapping: The Abou A'li river flood, Tripoli-Lebanon. Cartographie de risques: La que i la rivibre Abou A'li, Tripoli-Liban. M.R.Ktrawlie. Ameican University ...
Proceedings Seventh International Congress International As s ociation of Engineering Geology 5_9 SEPTEMBER 1994 / LISBOA / PORTUGAL {
Editors 1
I
R. OLIVEIRA, L. H RODRIGUES, A. G. COELHO INEC, Lisboa, Portugal
& A. P CI-INHA
OFFPRINT
1 u
A.A. BALKEMA / ROTTERDAM / BROOKFIELD
/ 1994
7th lntemational \AEG Congress
/
fu
Congres hbmational de AlGl,
a
1994. Balkema,
Rotterdam, ISBN W 5410
5O3
I
Hazardmapping: The Abou A'li river flood, Tripoli-Lebanon Cartographie de risques: La que i la rivibre Abou A'li, Tripoli-Liban M.R.Ktrawlie Ameican University of Beirut, Lebanon
ABSTRACT:Damages
from floods occurring at an increasing frequency. constrtute
a
heavy burden that must be checked. Though they are triggered by cllmatic extremes, affected areas are those intruded by man. A case study concentrates on the river Abou A'1r flood of 1955 affectin.q 400kmz includrng the second largest city, Tripoli, and ^creating huge damages and 400 people 9ead. The 42km long rrver drarns 595kmz with an annual flow of 262 mtllion mJ. Its terrain is of a The climatic regime complex geology, wlth characteristics leading to rnstability. also shows lnstability tending towards semi.arld torrential preci.prtation. Altempts
are made to project the ciimatic pattern as a means for disaster preparedness. The potentials of overbank flooding for selectively hazardous reaches are estimated for different tlme i.ntervals. Hazard mapping emphasizes two components, the risk of immediacy and the vulnerability of failure. rdsultants des inondations, se multi.pli.ent h des fr6quences ascendantes consti.tuant un lourd fardeau qur doil 6tre blen cont11116. Quorque rncit6 par des changements extrdmes de climat, 1'6tre humar.n est le seul
RESUME:Les d6gdts
responsabl.. C'est une 6tude d€tai1l6e, mettant en relief f inondation du fleuvede Abou-A'ii, qui a eu Lieu en 1955, et qui a aff6ct6 une superficie de 40Okm2, arnsi que 400 morts dans la seconde CapLtale du pays, Tnpoii. Abou A'li est un fleuve de 42km de long, irriguant une superfi.cre de 595kmz avec un d6btt annuel de 262 millionsde m3. - La g6ologie de la r6gion est tr6s complexe et instable. Le r6gime climatologique est du type serni-ande. Des tenlatives pour 6tablir une prdventron d-es calastrophes h parlir de modiles climatologiques sont drscut6es. La cartographie de risque souligne 'deux c_omposantes:.les rrsques dans les proximit6s idu fleuve et 1a vulndrabilitd de glissemenl. 1
INTRODUCTION
The last two decades in Lebanon, and along the eastern Mediterranean, have vitnessed an increasing frequency of disasl.ers, notably from floods. Obviously, not having undertaken disaster preparedness plans in the country, the resulting damages are rndeed qurte burdensome. The main cause behind these floods is the climati,c pattern overtakinthe regron, Lebanon, lyrng.between lattrtudes 33o 03 N-34o 45 N and longrtudes 35o 05'E - 360 30 E, rs a typical area feeling the impact of world-wrde climatic change (Bradley et al.,1987)expressed by some climatic extremes becoming common, The di.sasters,however are concentrated in those spots where man lnterferes,as shown by land use along river courses.
The purpose of thj,s investigation is to contr.ibute to controlling the potential damages by tryi.ng to mitigate flood
effects through hazard mapping of
a
river course. A promi,nent fiood took place along River Abou A'lr in northern Lebanon in 1955 (khawlie,1993). The scale of the river, the flood i"tself and its impacts make 1t an interesting case study. The Lebanese terrain, comprised of a huge mountain mass with the Mediterranean sea facing it to the wes1, consti.tutes a particular geomorphic setting (Khawlie,i991 ; Lindh,1992).This setting plays a cruclal role in understanding the type and extent of the effects of floods (Jackson,1987).The climatic pattern, if indeed one is established, seems to reflect a tendency to a more semiarid or arid Mediterranean with an extended dry period and a torrential winter
2049
(Imeson & Emmer,1992). lf this climaric regime could be forecasted, then plans would be taken beforehand to possibly reduce the potential effects of flood damage. Hazard mapping of river courses, as exempiifred in this investigation on Abou A'ii River, must reveal the imme-
diacy of risk and vulnerability of fai.lure in link wrth the climate. 2 THE DISASTER FLOODS 1N LEBANON A nurnber of locaI studies noted that the followlng events occur in Lebanon in a general decreasing order of scale: Torrents, debris flows, floods, sheet f1ows, avalanches, rock-debris fa11, earth flow, slump and creep. The extent of some single event eg. a flood,howev,er, may be much larger than this general sequence depicts, A detailed scan was made of the disasters occurring in the wet season (November to March) from the year I97l to i99i, Tabie 1. These months \lrere pi.cked up because they showed the highest perclntages of precipitation annually over almost the last century standing, respecti.vely, as follows : Nov.l4.29%,Dec.20,57%, Jan.23.52%,Feb.18.68% and March 70.95%; whereas each of Oct,and Apr.did not exceed 5%. 'table I. Yea
Recorded disasters during the wel season from'1971 ro I99l
[reather
r
l97r
Table I clearly reflects the extent of the di.sasters which, although may not sound large at an internatjonal scale, are definitely catastrophic at the national scale. A notable feature is that 1n the tv/enty years time interval there was eighteen local river floods,1.e. one almost every year. Not less than l5O people deceased, thousands of cattles died, tremendous damage took place in property, structures, utili.ties, services and agriculture including loss of produce, forests and huge soil erosion.The financial losses, estimated at $265mi1lion, is_ obvtously too much for a poor country like Lebanon to handle. The loss averiges about $i3 million per year which by itself constitutes a heavy burden on the country's ailing economy. Although some areas receive these disasters more frequently, yet the damage has overtaken all the Lebanese terrain. The 28 major events descri.bed in the Table are distributed through the wet season starting wrth 2 in Nov.going up to 4 in Dec.,6 in Jan., and increasing to 7 or B in Feb, or Mar. This reflects that they are more frequent towards the second part of winter and the beginning of spring. lndeed, the contri.bution to increasing water flow in river courses from snow melt at early spring is a crucial factor.
Location or Area Affected
Extreme
torrcnlial raiI
l.L)
Ehmej,Kfar Seluan
1972
2.J
diilo
)975
3.F
torrenl s, floods,
lempest, avalanche
Faraya
t976
L.F
snov (at {00m elevation)
llint Jbeil
1971
5.F
torrenls, floods &
Akkar,Beqa'a,Antelias, Dbaiye, Beirut, Tripoli
6.
ditlo
Beirut, Zahle
Damage
(Financial Loss estimate million $) road failure, agricultural
damaAe (2)
ditto struciural failure, ships damage,water pollulion, electricity & phones out, agricu I tu re-4peopl
1978
r"r
7.1 8. t"l
snow
accumulalions
torrenl s, floods hailslorms,floods
Dbaiye
Bhamdoun,Aleih,Akkar,
storm
Zghorta,Koura, Batroun Cheikh Zennad, Machta Hasan & Machta Hammoud, Bkai'ar Ileirut, Tripo'li
torrents
Akkar,Chekka
lr.F
floor in Antelias river
Antelias
r9B0
t2.
hail storm Sea storm
198r
13. F
1983
r4.F
ditto;floods in: Al-Kabir rivea, el-11ot river; sea
1919
9.1
r980
l0.J l
Nl
lvind storm rain stoam, hail storr:, avalanches
e
deceased(15)
mountains
Choui.coastal stretch, IPC Refinery Chouf
all coastal cities, Beqa'a, el-Baidar, Batroun,Michmich, Fnaidek, Bcherri, A'qoura
2050
diilo dirto,cattles (5)
ditto & trains derailed, huge soil erosioniS) diito
(12)
roads & tunnel failure,
landsi ides agri cul tural destruction cattle (t8) communications (2)
structural failure, roads, agriculture, electricity & phones, seaports({) agriculture (2) huge damage in many sect ors
, c a t
tl es
( 22 )
Table I cont'd. l5.M
torrents & floods in riversi Kfarchima, Hauch Harimi (Litani), el-Awali, Barghouth, & sea slorm, hail-slorm & avalanches
South Lebanon, Hasbaya' Bkai'a,Chouf,Beqa'a' Broummana, el-Ballout'
el-Kharroilb'Bar elias'
Choueifat'Akkar,Rihan'
1986
heads(68)
erri, Fak ra , O'i u n Siman, 5ir, Ainata,Cedars' all coastal cities Ni
\981
landslides, bridges,canals' roads, houses,shiPs, aqricul lure,foresl s,90 People deceased, 3000 cattle
h
a , Bch
l6.J
rain siorn,flood in Bisri river
tsisri,Sour
agriculture, soil erosion(l)
17.N
hailslorm
Bcharri,A'inata, Cedars
roads, forest (l)
r8.D
torrents,
Beirut,Hermel,Hasbaya,Ba'albek' Chouei r. H azze rt a QubaYat ' O'iulr Siman all mouniains
ditto'agriculture'
ditlo, port5, shiPs (6)
f9.J
avalanches
D
!{ind slorm, iorrents,
.
avalanches
roads, a.griculture (3)
2O.f
ditto,&Sea storill with huge uaves
all coasial cities
2l.N
torrents,flood in Ka lb river dilto, Iloods in Berdawni & Hasbani rivers
Zouk'Dbaiye
roads,canals({)
Beirut & suburb'5our'Zahle'
landslides, huge destruction in struclures, roads' Ports, Dublic services, agrlcullure' iso)ating communities'callles
Storm & torrents
all coaslal stretch, Akkar Ba'albek, Hermel, Rachaya Younine, Fakha, Nahle
landslides, communications(2) hu.qe destruction I Person
dilto & sea storm vith huge waves, flood in Ibrahim river & Beirul river ditio,flood in Auali river, Kasimieh river' Ghadir river
Saida,'Ankoun, KfariHetra,Cl.ouf; Ras Bayyada, ,Zouk, Yahchouch ' Beirut, ]bei1 & surroundrng
ditto 4 persons deceased(32)
21.M
torrents
Tripoli,
28.M
ditlo,flood in Bared river
Beqa'a,Ba'albek'Hermel
22.D
Mairouba
Hasbaya, Rachaya' Sir
(
1987
23.11 ?/..O 25.D
l98B
t99l
cattles(5)
,
26.F
torrents, flood in A'asst aiver
saida, chouei'at Dba
iye
Akkar'coastal cities
r8)
-
N
\
t
^
T36166
"i
,",)i(-t:.,25
Possibl.
of Noven&r
h!z.rd eguival.nt rain mi
>?@
rathe! lor
o.casional Mde.ale peak N6v -
2. NorFal or Uod..ate
.ilh.. 10-20
?130
