Invitation to Tender: Catchment modelling of NFM

Invitation to Tender: Catchment modelling of the potential effectiveness of Natural Flood Management for reducing flood risk to Keswick through the Resilient Glenderamackin Project

• Funder: Natural Course project c/o West Cumbria Rivers Trust
• Published Date: 13th March 2023
• Closing Date: 31st March 2023
• Contract Start Date: 10th April 2023
• Contract End Date: 1st July 2023

Please find full application document below.

Description of required works:

The overarching aim of the required analysis is to assess how effective Natural Flood Management features delivered through the Resilient Glenderamackin project could be at the flood risk to Keswick.

Using existing catchment models the following questions should be addressed:

• Can Natural Flood Management upstream of Keswick be effective in events with peak flows above the current standard of protection for Keswick (221.6m³/sec)?
• How does the distribution of the NFM features between the different sub-catchments impact their effectiveness on the downstream flood peak, i.e. where are the most cost-effective locations for siting NFM features?
• Could the addition of NFM features affect the synchronicity of flood peaks from different sub-catchments? How can peak flows be desynchronised to have the greatest impact on reducing flood risk in Keswick?

The analysis should consider large-scale temporary storage (e.g. large storage basins and floodplain reconnections), increased roughness and increased losses to evaporation and infiltration. West Cumbria Rivers Trust can provide information on where these interventions could be placed within the catchment and where interventions would not be possible or be inappropriate.

If the Resilient Glenderamackin project progresses to a delivery phase, feature scale modelling will be employed to ensure optimal feature performance for the target return period. Therefore, optimal performance of features (e.g. filling during the target return period) can be assumed for this modelling. Thirlmere Reservoir has a significant influence on flows in the River Greta. The dynamics of Thirlmere Reservoir should be considered as part of this analysis.

Gravel dynamics also influence flood risk in the catchment but do not need to be modelled in this analysis. The likely impact of gravel movement on the conclusions should be discussed.

The tender document should set out the proposed methods to address the above questions and identify if any further questions need addressing to ensure confidence in the project’s approach.

Required outputs

• A full report on the modelling undertaken including methods, findings and limitations.
• An executive summary that can be used to guide the aims of the Resilient Glenderamackin project and illustrate confidence in the project’s aims to non-specialist buyers.
• A short summary on proportionate flood risk modelling for NFM projects, using ‘Resilient Glenderamackin’ as a case study.

This piece of work is funded by the Natural Course project, which aims to reduce the barriers around delivery for the water environment across the North-West region. To ensure this piece of work has wider application, a summary should be produced outlining how flood risk modelling can be optimised to support project design without being cost prohibitive or inaccessible to practitioners.

Contact details

Caitlin Pearson, West Cumbria Rivers Trust

Phone: 07507 719469

E-mail: [email protected]