Saodi et al. (2023) Assessing the vulnerability of flash floods to climate change in arid zones: Amman–Zarqa Basin, Jordan

Identification

• Journal: Journal of Water and Climate Change
• Year: 2023
• Date: 2023-11-11
• Authors: Rihan Al Saodi, Mustafa Al Kuisi, Ahmed Al‐Salaymeh
• DOI: 10.2166/wcc.2023.237

Research Groups

• Department of Geology, School of Science, The University of Jordan, Amman, Jordan
• Department of Mechanical Engineering, School of Engineering, The University of Jordan, Amman, Jordan

Short Summary

This study assessed the vulnerability of flash floods to climate change in the Amman–Zarqa Basin, Jordan, by analyzing historical and projected climate data, land-use changes, and hydrological modeling. It found moderate vulnerability in downstream sub-catchments due to increased rainfall and insufficient stormwater infrastructure, while overall runoff is projected to decrease.

Objective

• To evaluate the sensitivity of flash floods to future climate change in the Amman–Zarqa Basin, Jordan.
• To determine trends in rainfall patterns.
• To assess the likelihood of flash flood occurrences based on climate change projections.
• To identify regions most vulnerable to climate change impacts.

Study Configuration

• Spatial Scale: Southwestern portion of the Amman–Zarqa Basin (AZB), Jordan, covering an area of 660 km². The area was divided into nine sub-catchments.
• Temporal Scale:
  • Historical: Daily rainfall (1970–2018), daily temperature (1988–2016), land-use maps (2001, 2011, 2021).
  • Projected: Daily General Circulation Model (GCM) data (2019–2060), future land-use (2041).

Methodology and Data

• Models used:
  • Watershed Modeling System (WMS 11.0)
  • Geographic Information System (ArcGIS 10.8.2, QGIS 2.16 with MOLUSCE plug-in)
  • HEC-1 simulation model (for runoff and peak discharge)
  • General Circulation Models (GCMs) and Regional Climate Model (RCM) (specifically CMCC-CM2-SR5, based on SSP5 scenario)
  • U.S. Soil Conservation Service (SCS) curve number (CN) method
  • Mann–Kendall test and Sen's slope test (for trend analysis)
  • Gumbel distribution (for Intensity–Duration–Frequency (IDF) curves)
  • Analytical Hierarchy Process (AHP) (for indicator weighting)
  • Sakib temporal flood intensity ratio (STFIR), Sakib flood damage avoidance potential (SFDAP), Sakib flash flood risk index (SFFRI)
• Data sources:
  • Historical daily rainfall: Ministry of Water and Irrigation (11 gauge stations)
  • Historical daily temperature: Ministry of Water and Irrigation (2 stations)
  • Projected climate data: Regional Initiative for the Assessment of Climate Change Impacts on Water Resources and Socio-Economic Vulnerability in the Arab Region (RICCAR)
  • Satellite images: Landsat 7 ETM+, Landsat 4–5, Sentinel-2 Missions
  • Digital Elevation Model (DEM): Shuttle Radar Topography Mission (SRTM) (12.5 m resolution)
  • Soil texture: Hunting Technical Services and Soil Survey and Land Research Centre
  • Stormwater drainage network: Greater Amman Municipality and Zarqa Municipality
  • Population per locality: Jordanian Department of Statistics
  • Actual runoff measurements: Ministry of Water and Irrigation (Jarash Bridge station)

Main Results

• Historical Trends: From 1970 to 2018, the study area experienced a 14.61% decrease in total annual rainfall, with a significant decreasing trend in total monthly rainfall for March at six stations. Mean, maximum, and minimum temperatures increased by 7.3%, 5.8%, and 10.9%, respectively. Urban areas expanded by 14.76% (97.25 km²) between 2001 and 2021.
• Future Projections (2019-2060): The study area is projected to experience an average 5.26% increase in total annual rainfall, primarily in downstream dry areas, while upstream wet areas are expected to see a decrease. Mean annual temperature is expected to rise by 11.7% to 19.4 °C. Urbanization is projected to cover 51% of the study area by 2041.
• Flash Flood Likelihood & Runoff: A historical storm event (8–12 mm/h for 2 h) is projected to become more frequent, occurring every 5–10 years in wet stations and every 10–25 years in dry stations. Despite increased urbanization, overall runoff volume and peak discharge are expected to decrease across most sub-catchments due to projected lower rainfall, though some downstream sub-catchments may experience increased peak flow.
• Vulnerability Assessment: Rainfall was identified as the primary controlling factor for flash flood incidents. No highly vulnerable sub-catchments were identified. Downstream sub-catchments 8 and 9 exhibited moderate vulnerability (score 6) due to high exposure (projected increase in rainfall and runoff) and low adaptive capacity (insufficient stormwater drainage infrastructure and limited vegetation), despite low population density and urban extent. Sub-catchment 1 also showed moderate vulnerability (score 5).
• Flash Flood Risk: Sub-catchment 9 showed the highest projected increase in flood intensity (STFIR = 1.9) and the highest overall flash flood risk (SFFRI = 1.27). Sub-catchments 6 and 5 had the lowest flood damage avoidance potential (SFDAP = 31%), indicating a critical need for adaptation measures.

Contributions

• Provides a localized and comprehensive assessment of flash flood vulnerability to climate change in an urbanized arid region (Amman–Zarqa Basin, Jordan).
• Integrates historical and future climate projections (using RCM data based on SSP5 scenario) with land-use change analysis and hydrological modeling.
• Utilizes a multi-criteria vulnerability assessment framework incorporating exposure, sensitivity, and adaptive capacity indicators, weighted by the Analytical Hierarchy Process (AHP).
• Introduces and applies Sakib's formulas (STFIR, SFDAP, SFFRI) for assessing spatio-temporal changes in flash flood intensity, damage avoidance potential, and risk.
• Offers transferable methodologies for evaluating hydrological responses to climate change in similar urban watersheds within arid regions.

Funding

This research was accomplished during a sabbatical leave offered to Prof. Dr. Mustafa Al Kuisi from the University of Jordan (October 2021 to September 2022). Climatic data were provided by the Ministry of Water and Irrigation, Greater Amman Municipality, and RICCAR.

Citation

@article{Saodi2023Assessing,
  author = {Saodi, Rihan Al and Kuisi, Mustafa Al and Al‐Salaymeh, Ahmed},
  title = {Assessing the vulnerability of flash floods to climate change in arid zones: Amman–Zarqa Basin, Jordan},
  journal = {Journal of Water and Climate Change},
  year = {2023},
  doi = {10.2166/wcc.2023.237},
  url = {https://doi.org/10.2166/wcc.2023.237}
}