Methods for Studying Maximum Flows. Application to the Wadi Sebdou Watershed (Tafna - NW Algeria)

Abstract

The estimation and predetermination of extreme flood quantiles is a necessary step in the studies of strategic projects for the prevention and management of flood phenomena in at-risk watersheds.

The OuedSebdouwatershed is a tributary of the Tafna, with an area of 439.3 km2, characterizedby a semi-arid climate. It has an elongated form, with a lithology that favorsflow (Bouanani, 2004).

The objective of this study is to analyzethe morphological characteristics, the rainfall regime and the determination of the frequency of floods, using the different empirical formulas that have been developed in the Algerian context for use in specific areas. The errors generated by the application of these formulas can lead to serious technical, financial and environmental problems such as a wrong dimensioning of storage or protection works, an erroneous cartography of the floodable zones whose consequences would be disastrous.

In this work, the analysis of the error of using these formulas in the Sebdou sub-basin was established. Also, the Gradex method was tested in this study. The results indicated that the GIANDOTTI method is the most reliable with a relative error of 19.7% (T=1000years), and the formulas of SOKOLOVSKY and TURRAZA are satisfactory and give flows close to those obtained from observations in the Sebdou hydrometric station.

Keywords. Oued Sebdou, Tafna, Maximum flows, empirical formulas, Gradex.

Received. December 14, 2022. Accepted.February 14, 2023. Published. April 16, 2023