The Role of Clay Quarries in Moderating the Effects of the Floods of 20 September 2020 in the City of BNI Hassen (Sayala basin)


Authors : Azaiez Naima; Zoghlami Karima; Nawal Qhtani

Volume/Issue : Volume 7 - 2022, Issue 5 - May

Google Scholar : https://bit.ly/3IIfn9N

Scribd : https://bit.ly/3NiyoBM

DOI : https://doi.org/10.5281/zenodo.6691802

Abstract : The subject of mining and the spread of openpit clay quarries in relation to the problem of flooding has generally been treated in a causal sense. Generally, the extraction of useful substances leads to a disturbance of the ecosystems, even if the contractors commit themselves to meeting the standards and criteria indicated in the contract specifications during the exploitation and rehabilitation phases. During the last two decades, flooding has become more frequent and severe in the agglomeration of Bni Hassen. The residential areas have invaded the majority of the land previously subject to the overflowing of streams and floods. For their part, the structures of "maskats" held upstream by a system of "Mgouds" and "Rabtas" are no longer capable of capturing runoff water as before. Despite the dredging of the bed of Wadi Sayala and its channeling in 2019, the floods of September 20, 2020, have caused loss of life and considerable damage to property, including infrastructure and agricultural land. This disaster could have been much more serious and its consequences heavier on the inhabitants if it had occurred outside the context of the exploitation of useful substances. In fact, the excavation pits played the role of real retention basins that surround the convergence zone of Wadi Sayala and Wadi Gamgoum. The study area had more than 29 mining pits with a depth between 5 and 47m. The objective of this research is twofold. First, to study the manifestation of the flood of September 20, 2020, in the watershed of wadi Sayala. Then, to make an estimate of the volume of water retained in the pits, which will be at the end the subject of a classification in term of storage and infiltration. This study shows that the total volume of runoff was reduced by 18% thanks to the presence of extraction pits.

Keywords : clay quarries, hydrological modeling, risk of flooding, hydrosystem of the Sayala wadi.

The subject of mining and the spread of openpit clay quarries in relation to the problem of flooding has generally been treated in a causal sense. Generally, the extraction of useful substances leads to a disturbance of the ecosystems, even if the contractors commit themselves to meeting the standards and criteria indicated in the contract specifications during the exploitation and rehabilitation phases. During the last two decades, flooding has become more frequent and severe in the agglomeration of Bni Hassen. The residential areas have invaded the majority of the land previously subject to the overflowing of streams and floods. For their part, the structures of "maskats" held upstream by a system of "Mgouds" and "Rabtas" are no longer capable of capturing runoff water as before. Despite the dredging of the bed of Wadi Sayala and its channeling in 2019, the floods of September 20, 2020, have caused loss of life and considerable damage to property, including infrastructure and agricultural land. This disaster could have been much more serious and its consequences heavier on the inhabitants if it had occurred outside the context of the exploitation of useful substances. In fact, the excavation pits played the role of real retention basins that surround the convergence zone of Wadi Sayala and Wadi Gamgoum. The study area had more than 29 mining pits with a depth between 5 and 47m. The objective of this research is twofold. First, to study the manifestation of the flood of September 20, 2020, in the watershed of wadi Sayala. Then, to make an estimate of the volume of water retained in the pits, which will be at the end the subject of a classification in term of storage and infiltration. This study shows that the total volume of runoff was reduced by 18% thanks to the presence of extraction pits.

Keywords : clay quarries, hydrological modeling, risk of flooding, hydrosystem of the Sayala wadi.

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