Chano et al. (2025) Comparison of Pluvial Flooding Modeling Software Applied in Highly Urbanized Settlements Using the Case of Lake Ganzirri

Identification

• Journal: Water
• Year: 2025
• Date: 2025-10-15
• Authors: José Javier Serrano Chano, Giuseppina Brigandì, Giuseppe Tito Aronica
• DOI: 10.3390/w17202978

Research Groups

• University School for Advanced Studies IUSS Pavia, Pavia, Italy
• Department of Engineering, University of Messina, Messina, Italy

Short Summary

This study compares pluvial flooding modeling software (EPA-SWMM 5.2, HEC-RAS 6.2, InfoWorks ICM 2021.9) in highly urbanized areas, focusing on the representation of buildings and Low-Impact Development/Sustainable Urban Drainage Systems (LID/SUDS) using the Lake Ganzirri area as a case study. It finds that a proposed building representation method in HEC-RAS 6.2 is comparable to the building void method in InfoWorks ICM 2021.9, and 2D LID/SUDS adaptations significantly increase infiltration volume despite minimal changes in water depth maps.

Objective

• To explore how to effectively represent key urban features, emphasizing buildings and low-impact development/sustainable urban drainage systems (LID/SUDS).
• To propose a method to represent buildings on a 2D domain and compare it with the widely used building void method.
• To explore the effects on the propagation of the runoff on a 2D domain when implementing LID/SUDS control elements as part of the 2D domain, and compare the outcomes with the regular representation of such elements using a 1D approach.

Study Configuration

• Spatial Scale: Lake Ganzirri area, Messina, Italy. The study area (excluding the lake) covers 154.92 hectares, with models focusing on an approximately 100 hectare case study.
• Temporal Scale: Simulations for 3-hour duration unimodal design rainfall events with 5, 10, 20, and 30-year return periods. HEC-RAS 6.2 used a computation interval of 0.1 seconds, while InfoWorks ICM 2021.9 used a 10-second time step.

Methodology and Data

• Models used:
  • EPA-SWMM 5.2 (Environmental Protection Agency—Stormwater Management Model)
  • HEC-RAS 6.2 (Hydrologic Engineering Center’s River Analysis System)
  • InfoWorks ICM 2021.9 (Innovyze’s integrated hydrological/hydraulic modeling software)
• Data sources:
  • Topography: Digital Terrain Model (DTM) and Digital Surface Model (DSM) (0.0167 meter resolution TIF files), ASC file (2 meter resolution).
  • Land/Soil Cover: CAD file detailing dwellings, buildings, parks, roads, and rustic drainage infrastructure. Building footprints from OpenStreetMap. Roads manually digitized using aerial photos.
  • Rainfall: Chicago-style hyetographs derived from a three-parameter Depth-Duration-Frequency (DDF) curve, based on 49 years of annual maximum rainfall data (1953–2006) from the Ganzirri rain gauge station.
  • Reference Data: A detailed 2D model created using InfoWorks ICM 2021.9 (Scenario S0) was used as the benchmark.

Main Results

• Building Representation (Comparison A): The proposed method for representing buildings in HEC-RAS 6.2 (combining Building with Solid Walls, Building Resistance, and Building Block methods) produced runoff propagation comparable to InfoWorks ICM 2021.9 (Building Void method). However, HEC-RAS 6.2 simulations had significantly longer computational times (average 4 hours 2 minutes vs. 1 hour 37 minutes) and required extensive manual mesh adjustments. Mean Absolute Error (MAE) for maximum depth ranged from 0.064 meters to 0.089 meters, and for maximum speed from 0.446 meters per second to 0.625 meters per second.
• 1D Pluvial Drainage System (Comparison B): Both InfoWorks ICM 2021.9 and EPA-SWMM 5.2 replicated the drainage system profile closely, though differences in relative depth at peak flow were observed, particularly in the right segment for stronger rainfall events, attributed to distinct infiltration methods.
• 1D LID/SUDS Implementation (Comparison C): Implementing LID/SUDS (green roofs, permeable pavements, bioretention cells) in 1D models (EPA-SWMM 5.2 and InfoWorks ICM 2021.9) reduced water depth and peak flow in pipes. EPA-SWMM 5.2 showed an average surface runoff decrease of 30.3% and an average final storage increase of 8.5 times. InfoWorks ICM 2021.9 showed a greater reduction in peak flow (43% vs. 30%) and relative depth (37% vs. 21%).
• 2D LID/SUDS Implementation (Comparison D): 2D LID/SUDS adaptations in InfoWorks ICM 2021.9 resulted in minimal, visually imperceptible, reductions in maximum water depth (average 1.5 millimeters) and speed maps. However, these adaptations increased the average infiltration volume by 62% across all rainfall events and decreased water flowing outside the 2D area by 9.1%. The inundated area was reduced by an average of 1.69 hectares.

Contributions

• Proposes and validates a method for representing buildings in HEC-RAS 6.2 using a combination of Building with Solid Walls, Building Resistance, and Building Block methods, offering an alternative to the building void method and addressing limitations for green roof representation in 2D domains.
• Explores the effects of implementing LID/SUDS control elements directly in a 2D domain, comparing it with the widely used 1D approach, demonstrating their impact on infiltration and runoff propagation.
• Provides a detailed comparison of three widely used hydrological/hydraulic modeling software packages (EPA-SWMM 5.2, HEC-RAS 6.2, InfoWorks ICM 2021.9) for pluvial flood modeling in highly urbanized areas, highlighting their advantages and limitations in urban feature representation and computational performance.
• Addresses the challenges of modeling highly urbanized areas with complex topography, dense buildings, and the absence of formal drainage systems, particularly in the context of protected water bodies.

Funding

• Italian Ministry for Universities and Research (MUIR)
• PRIN 2020 (Research Projects of National Interest) project: "Floods in cities: new INSights for integrating Pluvial floodIng into flood Risk maNaGement plans (INSPRING)", Grant Number: 2020NTSFXF.
• Scholarship co-financed by Ministerial Decree no. 352 of 9 April 2022, based on the NRRP—funded by the European Union—NextGenerationEU—Mission 4 “Education and research”, Component 2 “From Research to Business”, Investment 3.3.
• Company GetOpen Srl.
• Scientific Collaboration Agreement between the Department of Urban Planning of the Municipality of Messina and the University of Messina.

Citation

@article{Chano2025Comparison,
  author = {Chano, José Javier Serrano and Brigandì, Giuseppina and Aronica, Giuseppe Tito},
  title = {Comparison of Pluvial Flooding Modeling Software Applied in Highly Urbanized Settlements Using the Case of Lake Ganzirri},
  journal = {Water},
  year = {2025},
  doi = {10.3390/w17202978},
  url = {https://doi.org/10.3390/w17202978}
}