Empirical and analytical methods to characterize the efficiency of floods to move sediment in a small semi-arid basin - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Hydrology and Earth System Sciences Année : 2018

Empirical and analytical methods to characterize the efficiency of floods to move sediment in a small semi-arid basin

Résumé

Over a long multi-year period, flood events can be classified according to their effectiveness in moving sediments. Efficiency depends both on the magnitude and frequency with which events occur. The effective (or dominant) discharge is the water discharge which corresponds to the maximum sediment supply. If its calculation is well documented in temperate or humid climates and large basins, it is much more difficult in small and semi-arid basins in which short floods with high sediment supplies occur. Using the example of 31 years of measurements in the Wadi Sebdou (north-west Algeria), this paper compares the two main statistical approaches to calculate the effective discharge (the empirical method based on histograms of sediment supply by discharge classes and an analytical calculation based on a hydrological probability distribution and on a sediment rating curve) to a very simple proxy: the half-load discharge, i.e. the flow rate corresponding to 50 % of the cumulative sediment yield. Three types of discharge subdivisions were tested. In the empirical approach, two subdivisions provided effective discharge close to the half-load discharge. Analytical solutions based on log-normal and log-Gumbel probability distributions were assessed but they highly underestimated the effective discharge, whatever the subdivision used to adjust the flow frequency distribution. Furthermore, annual series of maximum discharge and half-load discharge enabled the return period of hydrological years with discharge higher than the effective discharge (around 2 years) to be inferred and showed that more than half of the yearly sediment supply is carried by flows higher than the effective discharge only every 7 hydrological years. This study was the first to adapt the analytical approach in a semi-arid basin and to show the potentiality and limits of each method in a such climate.

Domaines

Hydrologie
Fichier principal
Vignette du fichier
Megnounif Ouillon 2018.pdf (3.75 Mo) Télécharger le fichier
Origine : Fichiers éditeurs autorisés sur une archive ouverte

Dates et versions

hal-04369958 , version 1 (02-01-2024)

Identifiants

Citer

Abdesselam Megnounif, Sylvain Ouillon. Empirical and analytical methods to characterize the efficiency of floods to move sediment in a small semi-arid basin. Hydrology and Earth System Sciences, 2018, 22 (12), pp.6335-6355. ⟨10.5194/hess-22-6335-2018⟩. ⟨hal-04369958⟩
36 Consultations
11 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More