River Itchen Optioneering and Detailed River Restoration Design

River Restoration Summary

A 33-acre site of former water meadow, fen, and multiple river channels, previously managed as a premium game fishery, has been leased to the Hampshire & Isle of Wight Wildlife Trust (HIWWT) to oversee the development and implementation of floodplain restoration measures and long-term management. FLOW CIC were commissioned to deliver a consented, detailed design package of works to meet HIWWT’s objectives for the site. These were:

• Restore channel continuity (structures, weirs, and sluices) and rehabilitate the channel.
• Restore and enhance the channel planform.
• Restore and create connectivity with the floodplain, and enhance the riparian zone.

Requirements

To develop a river enhancement scheme ready for delivery, achieving the following objectives:

• Restore channel continuity (structures, weirs, and sluices) and rehabilitate the channel.
• Restore and enhance the channel planform.
• Restore and create connectivity with the floodplain, and enhance the riparian zone.

Approach

The project encompassed a comprehensive set of requirements to ensure a robust, environmentally sensitive design approach.

1. Project Initiation – Site visit with the landowners, HIWWT, and the Environment Agency Catchment Restoration Lead to agree on the project requirements and the process needed to secure regulatory approval and delivery.
2. Design Site Visit – On-site assessment to inform the design process, including the collection of drone imagery.
3. Topographic Survey – A full assessment of the target river reach’s topography, undertaken by the specialist Storm Geomatics.
4. Conceptual Design Development and Presentation – Creation and presentation of initial design concepts.
5. Detailed Design Package – Production of 2D CAD technical drawings using the topographic survey data, accompanied by a buildability statement.
6. CDM Documentation – Compilation of documents supporting the detailed design package, ensuring compliance with CDM 2015 regulations under the role of ‘designer’.
7. Environmental Consent – Liaison with the Environment Agency and Natural England to obtain a Flood Risk Activity Permit (FRAP) and SSSI Assent.

Outcome

A comprehensive design package and the necessary environmental permits were secured, making the scheme ready to progress to construction.

The package includes:

• 2D CAD river restoration designs
• Topographic river survey
• Pre-construction information to support the construction phase
• Design risk assessment, identifying and mitigating project risks
• Design evaluation outlining key considerations and potential constraints
• Buildability statement to inform the construction phase
• WFD scoping assessment of the scheme and its impact on the target waterbody
• Flood risk assessment of the scheme

Please find out more about our River Restoration Design Services here.