El-Haddad et al. (2026) Flood and heavy metal risks from wastewater site in Sohag Governorate, Egypt: integrating hydrological modeling and mapping

Identification

• Journal: Environmental Earth Sciences
• Year: 2026
• Date: 2026-03-21
• Authors: Bosy A. El-Haddad, A. Youssef, Shaymaa Rizk
• DOI: 10.1007/s12665-026-12873-w

Research Groups

• Geology Department, Faculty of Science, Sohag University, Sohag 82524, Egypt

Short Summary

This study evaluates flood inundation hazards and heavy metal contamination from untreated wastewater disposal sites in the Al-Kola Basins, Sohag, Egypt, by integrating hydrological models and geochemical analysis. It found that increased rainfall significantly exacerbates flood hazards and can mobilize high concentrations of anthropogenic heavy metals into critical surface water systems like irrigation canals and the River Nile.

Objective

• To evaluate flood inundation hazards and heavy metal contamination in the Al-Kola Basins, Sohag, Egypt, by integrating hydrological models and geochemical analysis.
• To determine if severe rainstorms, potentially due to climate change, could mobilize polluted soils and water from untreated wastewater sites to contaminate surface water elements (irrigation canals and the River Nile).

Study Configuration

• Spatial Scale: Al-Kola Basins, Sohag Governorate, Egypt, with a basin area of approximately 100 km². Digital elevation model (DEM) resolution of 12.5 m.
• Temporal Scale: Flood scenarios simulated for various rainfall depths (20 mm, 30 mm, 40 mm, 50 mm, 60 mm). Model validation used the 1994 rainfall flood event. Rainfall data records from 1970 to 2024 were considered. Geochemical analysis reflects current heavy metal contamination.

Methodology and Data

• Models used:
  • Geographic Information Systems (GIS) for spatial analysis, mapping, and data integration.
  • HEC-HMS (Hydrologic Engineering Center-Hydrologic Modeling System) for hydrological modeling (peak discharge, runoff volume).
  • HEC-RAS (Hydrologic Engineering Center-River Analysis System) for 2D hydraulic modeling (water depth, flow velocity, inundation maps).
  • DEFRA (Department for Environment, Food, and Rural Affairs) approach for flood hazard rating.
  • Sequential extraction procedure (Tessier et al., 1979) for heavy metal speciation in soil samples.
• Data sources:
  • ALOS PALSAR satellite DEM with 12.5 m spatial resolution.
  • Landsat OLI (30 m) for land-use data, verified with Google Earth images.
  • Soil map extracted from a 1:250,000 geological map and verified through fieldwork.
  • Historical rainfall records (1994 flood event) and meteorological observations (1970-2024) for rainfall data.
  • Eighteen soil samples collected from surrounding wastewater sites for geochemical analysis (atomic absorption spectrophotometer).

Main Results

• Flood Inundation: Increasing rainfall depth from 20 mm to 60 mm resulted in:
  • Average water depth increase from 1.48 m to 2.29 m.
  • Average flow velocity increase from 2.41 m/s to 3.76 m/s.
  • Inundated area increase from 26% to 37%.
  • Extreme hazard level increase from 23% to 42%.
• Heavy Metal Contamination:
  • Concentrations of Pb, Cd, Co, Cu, Ni, and Zn in soil samples exceeded international baseline levels (e.g., maximum Zn 305.0 mg/kg, Cd 8.9 mg/kg).
  • Contamination factors (CF) ranged from moderate (Co: 1.6–2.7, Ni: 1.1–2.6, Pb: 0.93–2.7, Cu: 0.18–1.2) to very high (Zn: 0.77–10.2, Cd: 13.4–37.5).
  • Statistical analysis confirmed anthropogenic effects, with the organic matter fraction (F4) being a vital fraction for Pb and a second vital fraction for Cd, Cu, Co, Ni, and Zn, suggesting municipal wastewater leakage as a source.
• Contaminant Mobility: Heavy metals showed high mobility values: Cd (89.9–97.7%), Pb (80.7–96.5%), Cu (80.2–95.2%), Zn (58.2–93.1%), Co (43.8–73.3%), and Ni (35.9–76.0%).
• Environmental Risk: Floodwater, particularly under higher rainfall scenarios, can transport these contaminants to irrigation canals and the River Nile, significantly exacerbating health and environmental risks.

Contributions

• This study is the first to integrate coupled hydrological-hydraulic modeling with geochemical analysis to assess flood hazards and heavy metal contamination from wastewater sites in the Al-Kola region of Sohag, Egypt.
• It provides a comprehensive understanding of how flood events can mobilize anthropogenic heavy metal pollutants, highlighting a critical environmental and public health risk in arid regions with untreated wastewater disposal.
• The research offers valuable information for developing informed flood risk management strategies and engineering suggestions (e.g., flood control structures, enhanced wastewater treatment, buffer zones) to mitigate pollutant spread.

Funding

• Open access funding provided by The Science, Technology & Innovation Funding Authority (STDF) in cooperation with The Egyptian Knowledge Bank (EKB).

Citation

@article{ElHaddad2026Flood,
  author = {El-Haddad, Bosy A. and Youssef, A. and Rizk, Shaymaa},
  title = {Flood and heavy metal risks from wastewater site in Sohag Governorate, Egypt: integrating hydrological modeling and mapping},
  journal = {Environmental Earth Sciences},
  year = {2026},
  doi = {10.1007/s12665-026-12873-w},
  url = {https://doi.org/10.1007/s12665-026-12873-w}
}