Hill et al. (2026) From reach to catchment-scale impacts: High-resolution hydrodynamic modelling of Nature-based solutions in the Cocker Catchment, UK

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2026
• Authors: Bartholomew Hill, Qiuhua Liang, Huili Chen, Lee Bosher
• DOI: 10.1016/j.ejrh.2026.103178

Research Groups

• School of Natural Sciences, University of Lincoln, United Kingdom.
• UNESCO Chair in Informatics and Multi-hazard Risk Reduction, Loughborough University, United Kingdom.
• Water Engineering Development Centre (WEDC), Loughborough University, United Kingdom.
• School of Business, University of Leicester, United Kingdom.

Short Summary

This study utilizes a high-resolution, GPU-accelerated 2D hydrodynamic model (HiPIMS) to evaluate the effectiveness of leaky wooden barriers across the 145 km² Cocker catchment. The findings reveal that while Natural Flood Management (NFM) features provide measurable flood attenuation and peak reduction during moderate rainfall events, their impact is significantly diminished during extreme events like Storm Desmond.

Objective

• To investigate the catchment-scale influence of Natural Flood Management (NFM) features (specifically leaky wooden barriers) on flood behavior using high-resolution 2D hydrodynamic modeling.
• To assess how spatial resolution and event magnitude affect the simulated efficacy of NFM interventions.

Study Configuration

• Spatial Scale: 145 km² (Cocker Catchment, Lake District, UK), utilizing grid resolutions of 2 m and 4 m.
• Temporal Scale: 48-hour simulation periods for two distinct events: the extreme Storm Desmond (2015) and a moderate high-rainfall event (2021).

Methodology and Data

• Models used: HiPIMS (High-Performance Integrated hydrodynamic Modelling System), a 2D shallow water equation solver accelerated by Graphics Processing Units (GPUs).
• Data sources:
  • 1 m resolution airborne LiDAR (UK Environment Agency).
  • UAV-derived Digital Terrain Models (DTMs) for explicit representation of 53 leaky wooden barriers (LWBs).
  • UKCEH Landcover Map (10 m resolution) for Manning’s roughness parameterization.
  • Rain gauge data from Cornhow and Honister Pass (15-minute resolution).
• NFM Representation: A "DEM breach" technique was employed to represent the leakiness of larger barriers, combined with localized increases in Manning’s roughness (n = 0.5) for the barrier footprints.

Main Results

• Event Dependency: NFM effectiveness was highly sensitive to event magnitude. In the moderate 2021 event, the site-scale peak water level was reduced by 14.33% (at 2 m resolution). In the extreme 2015 event, downstream peak reductions were modest (typically <1%).
• Resolution Sensitivity: The 2 m resolution model significantly improved the representation of flow pathways and barrier functionality compared to the 4 m model, particularly at the site scale where the Nash-Sutcliffe Efficiency (NSE) for the site gauge improved from 0.276 to 0.650.
• Storage and Attenuation: NFM features increased localized water storage by approximately 2004 m³ to 2837 m³. During the 2021 event, this translated to a maximum flood height reduction of 50–120 mm near the intervention site and 0–20 mm further downstream in Cockermouth.
• Property Impact: In the 2021 simulation, 37 properties experienced a reduction in flood risk (>10 mm depth reduction), with a maximum reduction of 103 mm for one property.

Contributions

• Provides the first large-scale (145 km²) application of a 2D hydrodynamic model that explicitly represents small-scale (<5 m) NFM features.
• Establishes a transferable framework for assessing NFM efficacy by integrating UAV-derived high-resolution topography with catchment-scale hydraulic modeling.
• Addresses the "evidence gap" regarding the performance of nature-based solutions in catchments exceeding 100 km² during high-intensity rainfall.

Funding

• Engineering and Physical Sciences Research Council (EPSRC) Centre for Doctoral Training in Water and Waste Infrastructure Systems Engineered for Resilience (WaterWISER; Grant: EP/S022066/1).
• Department for Environment Food & Rural Affairs (DEFRA), UK (Water Environment Grant and Green Recovery Challenge Fund).

Citation

@article{Hill2026From,
  author = {Hill, Bartholomew and Liang, Qiuhua and Chen, Huili and Bosher, Lee},
  title = {From reach to catchment-scale impacts: High-resolution hydrodynamic modelling of Nature-based solutions in the Cocker Catchment, UK},
  journal = {Journal of Hydrology Regional Studies},
  year = {2026},
  doi = {10.1016/j.ejrh.2026.103178},
  url = {https://doi.org/10.1016/j.ejrh.2026.103178}
}

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