conférence CAIRO flash flood in Algeria prof BENAZZOUZ

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  • Les crues rapides en Algrie: cas dAlger, ghardaia, Constantine, Batna

    Les consquences: dgts, sinistres Recherche des causes La gestion des risques en Algrie: loi 2004, catnat, tat civil,

    relogement Identification des problmes et checs: extension urbaines sur

    les berges des oueds Rcurrence des inondations en Algrie, au Sahara Perspectives, recommandations Carto des zones inondables Dveloppement des systmes dalerte des crues SAC : capteurs Installation de repres des crues historiques (hauteur) Information , vulgarisation Carto hydrogomorphologique

  • A torrential flood in urban area :a catastrophic event

  • Air de France

    395m

    N

    Bouzareah

    BASSIN VERSANT DE L'OUED KORICHE

    o.Ben Lazzhai

    o Sidi.Medjbar

    o. Frais-Vallon

    o.Scot

    to

    o. beau-Fraisier TrioletS1

    S3/Passerelle

    S2/Passerelle scotto

    El.Biar

    o.Kori

    che

    Bab.el.Oued

    Casbah

    MER MEDITERRANEE1m

    section et passerelles(S/P)

    Echelle:1/25 000

    Legende:limite du bassin versantouedslimite de sous-bassins

  • Reconstitution of the maximum envelop of flood with the remains to evaluate the importance

    of volumes occured

  • Street COLONEL LOTFI (since clearing) the water level measured is 2,2meters which gives a flow max of 143 m3/sand a contribution of 451.000 m3

  • 02

    4

    6

    8

    10

    12

    14

    16

    18

    20

    9h30 11h00 12h30 14h00 1 h30 18h00 19h30 21h00 23h00 0h30 2h00 3h30 h00 h30 9h30 11h00 12h30

    PLUIE(mm)HYETOGRAMME DE PLUIE DE L'EVENEMENT DU 9 ET 10 NOVEMBRE 2001

    te

    30mmavecuneintensitmaxde7,5mm

    143mmentre00Het13H30mm19mm(3H003h 30mm)19mm(11H0011h 30mm)19mm(12H0013h 30mm)

    127,8mmde18h06hdumatinBouzareah

    The intensity of rainfall before the major event of flash flood

  • BOUZEREAHannes Pj mm date1911 134 31-10-1911

    1934 101,4 21-09-1934

    1935 129,4 11-11-1935

    1936 100,5 9-12-1936

    1954 114,5 8-4-1954

    1964 108,3 8-11-1964

    BIR MOURAD RAIS

    annes P j mm date1954 135,2 2-2-1954

    1957 108,3 9-10-1957

    1964 104,5 8-11-1964

    1969 106,5 27-12-1969

    1974 94,6 29-3-1974

    1984 115 9-10-1984

    2001 145 10-11-2001

    TheexaminationofthesetofpluviometricdatarecordedatthestationofBirMouradRasandthestationof Bouzarah revealsthatquantitiesofsoimportantrainswerealreadyobservedbefore

  • Ajustement a une loi de GUMBEL

    des pluies Max jounalires 1951-2000

    STATION DE BIRMANDREIS CODE :020509

    Annes Pluies Annes Pluies Annes Pluies journalires

    journalires journalires 1986 64

    1951 61,5 1970 86,4 1987 45,2

    1952 48,9 1972 136 1988 75

    1953 135,2 1973 94,6 1989 58

    1956 27,5 1974 57,4 1990 30,5

    1957 108,3 1975 57,9 1991 55,4

    1958 77,8 1976 46,8 1992 69,4

    1959 74 1977 58,4 1993 691960 44,8 1978 87 1994 45,4

    1963 85,5 1979 56 1995 75,3

    1964 104,5 1980 41,2 1996 57,2

    1968 53,9 1981 57,1 1997 58,7

    1969 106,5 1984 115 1998 38,6

    1985 38,1 1999 64,5

    2000 47,7

    PJ du 10 novembreFrquence thorique. 0,989

    Priode de retour 90 ans

    The statistical analysis of this series for the period of 1951 to 2000 makes it possible to locate in frequency the rainy event which has

    occurred November 9th and 10th 2001 around one period of 90 years return (occurrence of the event in time)

  • TRIOLET market (receptacle of all sediments coming from upstream)

    The flash flood occured since 2 HOURS

  • Rachid KOUACHE street ( the pavement of the road is below 4 meters)

  • The first floor of a house completely buried on the Sidi-Medjber wadi

  • (712 died, 115 missings, 311 wounded and more than 1454 families without shelter),

    destroyed and buried of 389 vehicles all confused categories),

    extensive damage caused with the infrastructures: (deteriorations of the roads, formation of craters of more than 10 meters in diameter,

    strongly damaged networks of cleansing, silting of streets etc .....), Degradation of the buildings ,school, and houses

    (55) landslides, erosion and destabilisation on the

    foundations and elements of the structures.). economic costs (evaluated to 544 million algerian

    dinars of damage)

  • Organization of the helps Rehousing of the disaster victims and transfer of the

    populations towards external sites Clearing of the affected sites Program of rehabilitation of the networks Refitting of the site with work of confortement and

    protection against the flood Promulgation of insurance against risks (CATNAT) for

    any construction installed on sites exposed to the risks of flood

  • InondationsdeGhardaiaLeMzabestunplateaurocheuxdontl'altitudevarieentre300et800mtres.Cerelief,quidateducrtacsuprieur,seprsentesouslaformed'unevastetenduepierreuseetderochesbrunesetnoirtres.L'oued M'zabtraverseceplateaudunordouestverslesudest.

    Al'origineleMzabtaitunensemblede5oasis de72km600kmausudd'Alger :

    GhardaaBeniIsguenElAteufMlikaBouNoura

    etdedeuxoasisisolsplusaunord :BerrianGuerrara.

    PresentationLouedMzabprendnaissance750mdaltitudelamontdAitBelkacem,laltitudeminimaleest490m.LasuperficiedubassinversantElatteufestde1575km2,lalongueurdutalwegestde75km,letempsdeconcentrationestde27h.laP10maxestde37.2mm(nc)LaP100maxestde62mm(nc)LaP1000maxestde77.8mmDonnes:80annesdedonnespluviomtriqueslastationdeghardaia.

  • Main urbain areas affected by the flash floodin october 1st 2008

  • Waves of Flash floods carrying vehiclesand affected floor of houses

    Ghardaia, octobre 2008

  • Sept 28th 2008: 11mm

    sept 29 th 2008: 40.5mm

    A rain of an intensity of 15mm/h occurred between 21:00 to 22:00 on 29th sept

    on 30 sept a rain between 3:00 and 4:00 h in the morning of an intensity estimated at 150mm/h.

    -October 1st, 2008 ........ a strong rainfall between 3:00 and 4:00 in the morning with an intensity of 28.2mm/h.

    In the morning of October 1st, and following the 28.2mm, a devastator flash flood appears on the wadi Mzab with general and catastrophic overflow

  • the analysis of the flash flood leads to an estimate flow with 1200 m3/s. It is an exceptional flood since it reached sebkhet Sefioune situated at

    approximately 180 km in the South of Ghardaa cityat Metlili, one recorded 6 m height, whereas downstream from Ghardaa, this one reach a high of 8 m.

    according to J. Dubief, who worked more than 40 years on pluviometry in the Algerian Sahara,he retains the fact that at the time of the flood reaches sebkhet Sefioune, one can consider that this one is fiftieth (50 years), as such event return every 50 years.

    On the chronological level, the first devastator flash flood goes back to 1306, another exceptional flood happened on octobre 1884, but that of the September 30th, 1901 was reported with the maximum of details, with height of the water reached 10 meters; As by chance, it corresponds to the event of September 30th, 2008.

    the exploitation of the files of Ghardaia from period 1901 to 2008 makes it possible to raise approximately a hundred flood events

  • In consideration of the total destruction of many houses and the loss of the personal effects making it possible to identify the citizens, an initiative of the State consisted in installing permanently various services of the Civil state to be able to reconstitute the filiation of the disaster victims of the catastrophe

  • Destruction of the dam

    Detail of the bottom of the lac

  • From September 11th to 12th it rains 80 mm in 24 hours, While the annual total of the town of Biskra reachs 100 mm

    The damage 9790 palm trees 164 flooded houses 744 destroyed greenhouses 200 hectares of lost cultures

  • The courses of thethree wadis of Tazoult,BougdaneandAssebhad been deviated in 2003towards the Southern exit of Batna.the project consists of the realization of agallery in rock eight meters in diameter,a hard gallery of 476 meters long10,5 km of channels and ditchesThe results of this management dont seem effective facing the extent of the the floods.Piedmontwhich react with a prompt responsecompared to some rainy event.

  • Recurrences of the floodingin Constantine town

  • February 21st, 1852 November 6th, 1854 November 23rd, 1956 January 19th, 1958 November-December 1967 September 1973 April 16th, 1979 From December 28th to 30th 1984

    and October 3rd, 1994

  • Generally the causes of the floods in Algeria can be classified in 3 types

    1. remarkable weather resulting in a strong rainfall (important rains, storms) such as

    floods of December 1957 and March 1974 on Algiers and Sebaou basins The catastrophic floods of March 73 in eastern Algeria . floods of the autumn 1969 in Algeria and Tunisia The floods of December 1984 affected all the Algerian country

    2 . anthropic actions(failures of the various networks, embcles of the wadis by

    the debris, anarchistic urbanization of the rivers banks

  • 3 - Differentiated Relief contact mountain-plain, outlet of a

    valley Annaba, Biskra, MSila cities crossed by wadis

    ( Bordj Bou Arreridj,Oued Rhiou, Sidi Bel Abbes)Saharan cities: Tamanrasset, Bchar,Ghardaia

    cities located on Piedmont( Ain Defla ,Batna ,Mda)

  • Objectives1. improvement of the knowledge of the risks,

    reinforcement of their monitoring and their forecast as well as the development of preventive information on these risks

    2. the taking into account of the risks in the use ofgrounds and in the construction industry as

    well as the reduction of the vulnerability of the people and goods with the risks

    3. the installation of devices having for objectiveassumption of responsibility coherent,

    integrated and adapted of any catastrophe of natural or technological origin.

  • It is instituted: a planning of the helps for the assumption of responsibility of

    the catastrophes, in particular those resulting from the occurence of main risks, called plans ORSEC,

    - a planning of the particular interventions

    Plans ORSEC According to the importance of the catastrophe and/or

    means to implement, plans ORSEC are subdivided in: national plans ORSEC; - plans ORSEC inter-wilaya; - plans ORSEC of wilaya; - communal plans ORSEC; - plans ORSEC of the vulnerables sites.

  • The unhappy experiments of the past caused major damage which compromises any sustainable development in ourregions , any future installation must take account thisclimatic risk:

  • As regards prevention of the floods The general plan of prevention of the floods must content:

    a national map of inondability specifying the whole of the floodplains, including the

    beds of wadis and the perimeters located at the downstream of the dams and

    exposed for this reason in the event of rupture of dams

    the height of reference for each zone declared easily flooded, below which the

    perimeters concerned are burdened with the instituted constraint of non-aedificandi

    thresholds, conditions and procedures of release of pre-warning and warning for

    each one of these risks, as well as the procedures of end of warning.

    Without damage of the legislative measures in force, in the zones declared easily

    flooded by the general plan of prevention of the floods and located at the top height of

    reference, authorizations of occupation, of visa of construction must, under penalty of

    nullity, to specify the whole of work, installations, drains or works of correction

    intended to reduce the risk

  • 1. To controlinstallation of stations which measure and

    transmit in real-time the height of water2. To envisage

    collection of data to feed from the forecasting models (propagation of flows, transformation of the rain into flow for the upstream of the basins, hydraulic model

    3. To transmit informationinformation on the floods is collected or worked out by the services of forecasts of floods (Service de Prvision des Crues) is communicated in real-time on Internet by maps ( flood vigilances) which indicates the level of vigilance according to 4 colors

  • The PPRI aim not increasing the stakes exposed in floodplain and to preserve the fields of expansion of the flood

    In the urban areas, the rules of constructibility do not result only from the influence of local reference, but are modulated according to the type of urbanization of areas concerned:1. The not urbanized zones must remain it whereas in

    already urbanized spaces, of constructions can be authorized under conditions (project exposed to a strong or average risk)

    2. Protected spaces by dams remain zones subjected to the risk, because one cannot have of absolute guarantee on the effectiveness of the works), consequently the spaces not urbanized behind the dams must remain it

  • To reduce the risk of flood, it is necessary to act in three directions:

    1. To reduce floods by acting on the phenomenon itself2. To reduce the vulnerability of the people and the goods

    to the events (to imagine the development in priority apart from the floodplains, controls and limit urbanization)

    3. To better know to live with the risk by developing the knowledge and the comprehension of the floods(to familiarize itself with the cartography of the floodplains, reference marks of the risings)

    Flash floodsin Algeria: impact and managementLes inondations en Algrie: sommaireThe flash flood of bab el ouedin Algiers November 10th, 2001 The catchment area of the Koriche wadi with its four tributary wadis The measured maximum water level (leaves of flood) is 2,45 m, which give a flow max 730 m3/s and a total contribution of 2.600.000 m3The empirical estimate of the carried sediments product a volume of 800.000 m3 6 7 8 9 10 11 12 13The assessment of the catastrophe of Bab el OuedDifficulties of Management post crisis FLASH FLOODS IN GHARDAIA October 1st, 2008 17 18Flash Flood in Ghardaia with overflow of the wadi in the near districts, October 2008 20Event analyzesCharacteristics of flash flood in GhardaiaDifficulties of management post crisis of the catastrophe in GhardaiaFloods in the Sahara desert at the area of DOUCENin Zibans, September 2009Destroy of a hilly dam in Zibans (Doucen)Consequences of the floods:losses of the dattes production, embcle across the bridges (Doucen September 2009)Saharan village in floodplain,high vulnerability (Chaiba, Zibans) low terraceand site of foum ( canyon)Road exposed to the floods: bridge submerged by the floods of the wadi Djeddi in Zibans (Biskra) , September 2009 FLOODS IN the ZIBANS region in 11th September to 12th, 2009Flood in Batna city April 26th 2006rainfall of 63 mm during one night FLOODS IN CONSTANTINEFloods of the Rhummel wadi at the entry of the canyon from December 28th to 30th 1984 and evacuation of 250 families who live on the low fluvial terraceHistorical floods in ConstantineCauses of the floods in AlgeriaCities on particular geomorphological sites are exposed to the risk of floodingPrevention of the majors risks and the natural catastrophes in Algeria , according to the algerian law 04-20 du 25 Dcembre 2004 planning of the helps and management of the catastrophes For a better management risk of flash flood Prevention of floods Monitoring and the forecast of flash floodControl of setllings in the zones exposed to the risk of flood: the Plan of Forecast risks of flood (Plan de Prvision des Risques dInondation)Which are the measures recommended to reduce the risk of flood?