Influence of considering tributaries to reconstruct flood hydrograph of an extreme event on the upstream portion of Medjerda River

Abstract

In Tunisia, flood problems arise from the only perennial river, Medjerda, in particular the Plain of Bou Salem where two tributaries (Mellegue and Tessa) and the main station of Jendouba discharge into. The inundation of January 2003 was a catastrophic event in the Bou Salem watershed. Hence this event was chosen for research to test the reconstitution of hydrographs by different methods and to analyze the effect of its tributaries. Two models are used; Muskingum and Regression to simulate the hydrograph at different calculation times (2, 4, 6 and 8 h). To evaluate the quality of reconstitution models, three performance criteria were selected: standard deviation error ‘S’, peak relative error ‘S1’ and peak time difference ‘S2’. The reconstitution of Bou Salem’ floods (downstream station) from Jendouba (upstream station) was set in four scenarios: (1) ignoring the tributaries, (2) considering the tributary Mellegue, (3) taking into account the tributary Tessa and (4) considering both tributaries of Tessa and Mellegue. Following this application, the fourth scenario reproduced well the flood peak and illustrated how important the consideration of tributaries was. Regression model gave the best values of performance criteria and simulated the discharges hydrographs well.

Key words: Flood, Mejerda River, reconstitution, tributaries, regression, Muskingum

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