Bouchikhi et al. (2025) Multi-criteria decision analysis and hydrodynamic modeling for flood-safe urban planning: case study of Oued Merzeg, Casablanca (NW Morocco)

Identification

• Journal: Natural Hazards
• Year: 2025
• Date: 2025-09-08
• Authors: Sara Bouchikhi, Mimoun Chourak, Maelaynayn El Baida, Farid Boushaba
• DOI: 10.1007/s11069-025-07641-1

Research Groups

• Industrial and Seismic Engineering Research Team, Mechanics and Applied Mathematics Department, National School of Applied Sciences of Oujda, Mohammed 1st University, Oujda, Morocco
• African Disaster Mitigation Research Center (ADMIR), NRIAG, Cairo, Egypt
• Laboratory of Modeling and Scientific Computation (LMCS), National School of Applied Sciences of Oujda, Mohamed 1st University, Oujda, Morocco

Short Summary

This study mapped flood hazard in Oued Merzeg, Casablanca, Morocco, using Analytical Hierarchy Process (AHP) and Iber hydrodynamic modeling, finding AHP more effective in identifying widespread flood stagnation areas compared to the hydrodynamic model's focus on fluvial dynamics. The research provides a dual understanding of flood hazard for urban planning and offers preliminary insights into nature-based solutions.

Objective

• To map flood hazard in the Oued Merzeg area of Casablanca, Morocco, by comparing and integrating Analytical Hierarchy Process (AHP) and hydrodynamic modeling (Iber) to provide a comprehensive flood hazard profile for urban planning.

Study Configuration

• Spatial Scale: The study area covers 13.58 km² within the Oued Merzeg watershed (395 km²), located 14 km from Berrechid in the Casablanca-Settat region, Morocco. Hydrodynamic simulations were performed at 4 m, 8 m, and 12 m mesh resolutions, while AHP mapping used a 12.5 m resolution.
• Temporal Scale: Long-term daily rainfall records (1974–2023) were used to derive a 100-year return period flood event. Validation was performed using observed flood points from January 1–15, 2021.

Methodology and Data

• Models used:
  • Analytical Hierarchy Process (AHP) for multi-criteria decision analysis.
  • HEC-HMS (Hydrologic Engineering Center’s Hydrologic Modeling System) for rainfall-runoff transformation.
  • Iber (2D hydrodynamic model) for simulating free-surface flows and flood dynamics.
• Data sources:
  • Topography: Digital Elevation Model (DEM) from ALOS PALSAR (12.5 m spatial resolution) for elevation, slope, drainage density, Stream Power Index (SPI), and Topographic Wetness Index (TWI).
  • Land Cover: Land Use Land Cover (LULC) from Sentinel-2 images (10 m resolution, ESRI Land Cover 2023).
  • Vegetation: Normalized Difference Vegetation Index (NDVI) from Landsat-8 data.
  • Rainfall: Daily rainfall data from Tamedroust hydrometric station (1974–2023) for hydrodynamic modeling; mean annual rainfall (Kriging interpolation from marocmeteo) for AHP.
  • River Network: Distance from the river derived from DEM.
  • Soil Parameters: SCS curve number model for HEC-HMS.
  • Validation Data: Observed flood points from World Bank sources (January 2021).

Main Results

• AHP Flood Hazard: The AHP map classified approximately 49% of the study area as high flood hazard and another 49% as moderate. High hazard zones were primarily located within 1200 m of the main river, in low altitudes (< 100 m), and on gentle slopes (< 5°).
• Hydrodynamic Flood Hazard (Iber): The 100-year return period event generated a peak discharge of 116.8 m³/s. Simulations showed water depths exceeding 5 m in coastal depression areas and higher velocities along the main river channel. Extreme and significant hazard levels were largely confined to the river corridor. Finer mesh resolutions (4 m) provided more detailed flood characteristics.
• Validation and Comparison: AHP demonstrated superior capability in identifying observed flood points, classifying 56.38% as "significant" and 0.49% as "extreme" hazard. In contrast, the Iber model identified 0.25% as "significant" and 0.36% as "extreme," with 99.28% of validation points falling outside its simulated flood extent. AHP's strength lies in capturing widespread flood stagnation areas influenced by geomorphological features, while Iber excels in precise fluvial flood dynamics.
• Nature-Based Solutions (NbS): A preliminary simulation of large-scale afforestation (reducing the SCS Curve Number to 70) indicated a significant reduction in peak runoff from 116.8 m³/s to 83 m³/s, highlighting the potential of NbS for flood mitigation.
• Urban Planning Implications: The study identified residential and industrial areas currently outside designated protected zones that are highly susceptible to inundation, necessitating immediate attention and integration of flood-resilient planning.

Contributions

• Provides a comprehensive flood hazard assessment framework by integrating a semi-quantitative multi-criteria approach (AHP) with a physically-based hydrodynamic model (Iber), offering a dual understanding of flood susceptibility and dynamics.
• Offers a comparative analysis of AHP and hydrodynamic modeling, highlighting their complementary strengths in identifying different types of flood hazards (widespread stagnation vs. fluvial overflow) in a data-scarce urban environment.
• Validates both models against observed flood events, demonstrating AHP's effectiveness in mapping broader flood susceptibility, particularly in urban and coastal stagnation zones.
• Presents a preliminary assessment of nature-based solutions (large-scale afforestation) for flood mitigation, showing its potential to reduce peak runoff and inform future sustainable urban development.
• Delivers actionable insights and recommendations for flood-safe urban planning in the rapidly urbanizing Oued Merzeg watershed, addressing critical infrastructure and residential development risks.

Funding

This work is part of a broader project titled "Enhancing Disaster Resilience in Arab Countries through Multi-Hazards Modelling and Mapping Using Machine Learning and IoT Sensors," funded by the Federation of Arab Scientific Research Councils (FASRC) and the Academy of Scientific Research and Technology (ASRT)-Egypt.

Citation

@article{Bouchikhi2025Multicriteria,
  author = {Bouchikhi, Sara and Chourak, Mimoun and Baida, Maelaynayn El and Boushaba, Farid},
  title = {Multi-criteria decision analysis and hydrodynamic modeling for flood-safe urban planning: case study of Oued Merzeg, Casablanca (NW Morocco)},
  journal = {Natural Hazards},
  year = {2025},
  doi = {10.1007/s11069-025-07641-1},
  url = {https://doi.org/10.1007/s11069-025-07641-1}
}