Watershed scale flood hazard modeling at the Hodna large basin in central Algeria
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Date
2023
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université msila
Abstract
Flooding is a huge problem worldwide, especially in North african countries. The Intergovernmental Panel on climate change (IPCC) has considered North Africa as one of the major regions facing climate change impact in the world. Flood risk is composed of three main elements, including hazard, exposure and vulnerability. In addition, flood damages have been increasing as a result of climate change, land use change as well as the increased number of residential areas along flood-prone areas. Therefore, assessment of flood discharge rates and flood risk is essential for a good management and mitigation measures. The Hodna basin has been considered for this research. With its large area equals to 26 000 km², the Hodna basin is the fifth largest basin in Algeria. It is an endorheic basin constitutes of eight sub-basins, among them the saline lake Chott-El-Hodna.
To respond to the previous mentioned issues, this thesis aims at: i) assess peak flows for different return periods (10-year, 50-year, 100-year and 1000-year) based on empirical and statistical formulas and extreme daily precipitation; ii) use the one dimensional steady flow hydraulic model of HEC-RAS software to assess the impact of these peak flows on provinces may be facing flooding risk in Hodna basin; iii) use the Geographic Information System (GIS) to generate flood hazard and risk maps on the basis of Analytical Hierarchy Process (AHP) technique ; iv) project average monthly precipitation and maximum temperature changes over the period 2021-2100 using the last generation of climate scenarios Shared Socio-economic Pathways (SSPs) and six climate models.
The flood risk map indicates that the cities of Sidi Aïssa, Boussaada, Barika, Bordj Bou Arreridj and M’sila are the most cities exposed to flooding risk. The application of 1D steady flow model shows the water heights at different parts in these cities. It reaches a maximum of 3.43 m in M’sila, 3.27 m in Bordj Bou Arreridj, 2.77 m in Barika, 4.16 m in Boussaada and 6.46 m in Sidi Aïssa for a 50-year flood. Besides, historical evaluation of the six climate models allows the validation of the best ranking model for both average monthly precipitation and maximum temperature variables. The models IPSL-CM6A-LR and GFDL-ESM4 have been used to project future changes over the period 2021-2100
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Keywords
flood risk; peak flow; return period; climate change; precipitation; GIS; HEC-RAS; SSP; Hodna basin; Algeria