Sabeti et al. (2026) Modelling Nature-Based Solutions in HEC-RAS

Identification

• Journal: Water Resources Management
• Year: 2026
• Date: 2026-01-01
• Authors: Ramtin Sabeti, Thomas Kjeldsen, Matt Chambers, Hamed Moftakhari, Luis Partida, Ioanna Stamataki, Solomon Simmonds, Rebecca Lee, Barry Hankin, Melissa Hoskings, Katherine Dixon, James Molloy, Muthukumar Narayanaswamy
• DOI: 10.1007/s11269-025-04379-0

Research Groups

• Department of Architecture and Civil Engineering, University of Bath, UK
• Institute for Resilient Infrastructure Systems, School of Environmental, Civil, Agricultural and Mechanical Engineering, University of Georgia, US
• Department of Civil, Construction and Environmental Engineering, University of Alabama, US
• School of Engineering, University of Greenwich, UK
• Faculty of Environment, School of Geography, University of Leeds, UK
• The Water Institute, Baton Rouge, US
• Land Management Team, Bristol Avon Rivers Trust, UK
• JBA Consulting, Warrington, UK
• JBA Consulting, Broughton, Skipton, UK

Short Summary

This study systematically reviews 1,080 publications to synthesize approaches for representing Nature-Based Solutions (NBS) in HEC-RAS hydraulic models, providing practical recommendations and linking interventions to governing hydraulic equations to standardize flood risk mitigation assessments.

Objective

• To provide a consolidated resource and practical recommendations for researchers and practitioners on how to represent Nature-Based Solutions (NBS) interventions in HEC-RAS and other hydraulic models, by systematically reviewing existing literature and linking interventions to specific parameters in governing hydraulic equations.

Study Configuration

• Spatial Scale: The systematic review covers studies with catchment areas ranging from 0.09 km² to approximately 2400 km². The recommendations are broadly applicable from reach to catchment level. A case study of the River Chew catchment (England) is presented in supplementary material.
• Temporal Scale: The systematic literature review covered publications from 2006 to 2024.

Methodology and Data

• Models used: HEC-RAS (1D, 2D, or 1D/2D). HEC-HMS and Dynamic Topmodel were mentioned as coupled hydrological models in some reviewed studies.
• Data sources: Systematic literature review of 1,080 publications from Scopus and Web of Science databases. Data extracted from 30 key studies included quantitative hydraulic outputs (e.g., inundation depth/extent, velocity, hydrographs) and parameter adjustments (e.g., Manning's n, Digital Elevation Model (DEM) modifications).

Main Results

• A systematic review of 1,080 publications, distilled into 30 key studies, provides a transparent, practice-oriented assessment of NBS implementation in hydraulic modeling, linking interventions to mass and momentum equations.
• The five most common NBS interventions (afforestation/reforestation, increased vegetation, wetland creation, flood retention lakes, and floodplain reconnection) can be integrated into hydraulic models by adjusting Manning’s n values or modifying Digital Elevation Model (DEM) topographies.
• Specific Manning's n ranges for afforestation/reforestation in HEC-RAS 2D are 0.0120–0.065 s·m⁻¹/³ and 0.15 s·m⁻¹/³ in HEC-RAS 1D. For increased vegetation, HEC-RAS 2D values range from 0.040 to 0.16 s·m⁻¹/³ and HEC-RAS 1D used 0.12 s·m⁻¹/³. Wetland scenarios in HEC-RAS 2D adopted 0.120 s·m⁻¹/³. Flood retention lakes involve altering topography/storage areas, and floodplain reconnection involves DEM modifications (e.g., berm removal, flood benches).
• A significant limitation is the limited explicit reporting of methods and parameter values in many reviewed studies, highlighting a critical need for future research to incorporate empirical validation and transparent reporting of modeling assumptions.

Contributions

This study provides the first comprehensive assessment and standardization effort for representing Nature-Based Solutions (NBS) interventions in HEC-RAS and other hydraulic modeling platforms. Unlike existing studies that develop case-specific approaches, this research synthesizes fragmented knowledge into actionable, structured guidelines, categorizing parameter adjustments and linking interventions to fundamental hydraulic equations, thereby initiating a pivotal effort toward standardizing methodologies for flood risk assessment.

Funding

• Leverhulme Trust project grant: RPG-2022-306
• Participate Grants (University of Bath)

Citation

@article{Sabeti2026Modelling,
  author = {Sabeti, Ramtin and Kjeldsen, Thomas and Chambers, Matt and Moftakhari, Hamed and Partida, Luis and Stamataki, Ioanna and Simmonds, Solomon and Lee, Rebecca and Hankin, Barry and Hoskings, Melissa and Dixon, Katherine and Molloy, James and Narayanaswamy, Muthukumar},
  title = {Modelling Nature-Based Solutions in HEC-RAS},
  journal = {Water Resources Management},
  year = {2026},
  doi = {10.1007/s11269-025-04379-0},
  url = {https://doi.org/10.1007/s11269-025-04379-0}
}