CONTRIBUTION TO THE STUDY OF PLUVIOMETRY DAY LABOURER OF THE NORTH OF ALGERIA

Mohamed MEDDI, Amel Talia

Résumé


Abstract:
These last years, the floods are disturbed the economic activities of certain regions of the country.
These floods caused considerable damage: habitat, basic infrastructures and agricultural production
in certain zones. Damage also recorded in many cities of the South and the North. The flood is an
exceptional phenomenon which can occur constantly. The flood is the occasional phenomenon,
consequence of the exceptional flood, which can drown vast parts. The control of the
predetermination, the quantification and the forecast of the flood allow a preliminary protection of
the people?s goods and exposed people, in particular by the designation of the zones of risks inside
of which the probability of occurrence of the catastrophe is sufficiently important.
In Algeria, the rains are characterized by a very strong interannual and seasonal irregularity. This
variability leads to extremely severe low water and strong flood and consequently considerable
human and material damage caused par the generated floods.
To give an outline on maximum daily pluviometry, ten stations having a sufficient measurements
series were studied.
The appearance of the daily maximum rains varies considerably from one month to another. For the
stations of the West and Center, the rains are concentrating in the winter?s months then the
frequency of appearance of these rains decrease notably in the spring?s months. For the stations
located at the east of Algeria, the concentration appears either in spring (February), or in winter but
with an important frequency of appearance over several months (October, November, December).
The nonparametric test of Pettitt, the statistics of Buishand, the Lee and Heghinian Bayesian
method and the nonparametric procedure of hydrometeorological series segmentation of Hubert
applied to the the daily maximum pluviometry series and the number of day of rain.
From the founded results, we retained that the East of Algeria, no significant rupture could be
detected. For the remainder of the Algerian territory and for the used tests, the rupture occurred
during the decade 1970-1980 and during this period the decrease of daily precipitations became a
reality.
By comparing daily precipitations (maximal daily rain, the number of rainy days superior to 0.1
mm, 1 mm and 10 mm) before and after 1974, we deduced that daily precipitations, on the level of
the West and the Center, recorded a considerable decrease. On the other hand, in the east of
Algeria, these rains knew an increase in a number of rainy days higher than a fixed threshold and
we noticed that the maximum rainy day passed from 1086 mm before 1974 to 1160 mm after 1974
on the level of the station of Annaba.
Bellow we will give some floods and their consequences. In the region of Annaba, the rain
recorded in 1982 has 110 years return period, 35 mm in the 40 minutes space. April 04, 1996, in the
same area, intense rains generated 5 died and 10 wounded. In Guelma, February 3, 1984, an
abundant rain produced 03 disappeared and 157 disaster victims? families with considerable
property damages. In Jijel, for the same rain, one noted 20 died. July 5, 1987, in Batna, a rain of 57
mm (period of 14 years return and half) caused 2 died and of the hundreds of disaster victims
families. During the days of January the 26, and 27 1992, a generalized rain touched the centre of
Algeria and caused deaths and many casualties. Rains of November 2002 on Algeria, and Algiers
in particular, gave place to hundreds of dead and disappeared with considerable property damages.
For a better risk management, it is important to control the knowledge of pluviometry finer scale to
make it possible to develop models likely to be used in the alarm systems.

Texte intégral :

PDF