Osborne et al. (2026) DIG-ging deeper: soil selection drives hydraulic performance in highway rain gardens

Identification

• Journal: Frontiers in Environmental Science
• Year: 2026
• Date: 2026-09-15
• Authors: Stuart McLelland, Mia Cole, Robert E. Thomas
• DOI: 10.3389/fenvs.2026.1901519

Research Groups

• Energy and Environment Institute, University of Hull, Hull, United Kingdom

Short Summary

This study evaluates the performance of nature-based solution (NBS) highway rain gardens developed under the Doncaster, Immingham, and Grimsby (DIG) Surface Water Resilience Project. Four rain gardens on a flood-prone highway in Grimsby, UK, each with an identical hybrid design combining attenuation crates with different soil media, were monitored over a full hydrological year.

Objective

• Quantify differences in vertical and lateral soil moisture dynamics, outfall response, and attenuation behaviour across four soil types within a standardised hybrid rain garden system under operational highway conditions.
• Compare rain garden soil behaviour against undisturbed natural soil to assess how closely each medium replicates natural hydrological function.
• Evaluate electrical conductivity (EC) patterns at rain garden outfalls as an indicative proxy for solute transport and water quality performance.

Study Configuration

• Spatial Scale: Highway rain gardens on a flood-prone highway in Grimsby, UK, with a catchment area of ∼360 m^2.
• Temporal Scale: Full hydrological year (October 2024- September 2025).

Methodology and Data

• Models used: None mentioned.
• Data sources: Field measurements from soil moisture probes, CTD probes, and rainfall data.

Main Results

• The recycled soil behaved most like the natural control, providing comparatively high retention at low cost.
• The standard engineered soils showed intermediate responses, with Soil A maintaining consistent moisture conditions and reducing peak outfall depth by 48% while extending outflow duration by 55% relative to the premium mix.
• Seasonal conductivity patterns indicated solute retention differences, especially during winter salting.

Contributions

• This study provides a unique opportunity to evaluate the performance of highway runoff rain gardens in a real-world setting.
• The findings show that no single soil performed best across all functions and highlight the importance of matching soil selection to site-specific hydraulic, environmental, and sustainability priorities.

Funding

• Not mentioned.

Citation

@article{Osborne2026DIGging,
  author = {Osborne, Wm. Alexander and McLelland, Stuart and Cole, Mia and Thomas, Robert E.},
  title = {DIG-ging deeper: soil selection drives hydraulic performance in highway rain gardens},
  journal = {Frontiers in Environmental Science},
  year = {2026},
  doi = {10.3389/fenvs.2026.1901519},
  url = {https://doi.org/10.3389/fenvs.2026.1901519}
}