The study aimed to improve the National Trust’s understanding of the hydrology of the land at Ormesby Hall including both surface and subsurface water. The feasibility and potential benefits of implementing strategically located NFM interventions in the landscape to reduce impact of water on infrastructure within the site, reduce impact of water draining from the site and habitat enhancement and creation were explored. The site posed a series of challenges to address in the analysis and design work including the A174 Parkway running through the site, splitting it into a north and south area; historic buildings, landscape features, protected parkland views across the site; and extensive historic land drains across the site with a lack of accurate records. Initial site investigations also highlighted the complexity of the site’s hydrology, for which the below diagrams were produced to simply explain the complex system.
The study included:
- Desktop review of historic imagery and maps, drainage records, LiDAR, hydrological data and other relevant landscape factors.
- Site investigations, observations and discussions with the National Trust and tenant farmer. This helped to confirm desktop mapping and clarify drainage features across the site. Soil samples and infiltrations tests were also taken.
- Baseline 2D hydrological modelling of site.
- Identification of interventions appropriate for the site and complement and improve existing heritage features.
- Development of a site-wide strategy that sensitively integrates the identified NFM within the landscape and reduces water draining from the site.
- Stakeholder design workshop and site walkover with the National Trust to present initial design options and gain feedback from relevant members of the National Trust.
- Development of the design strategy into a full masterplan.
- 2D hydrological modelling of the proposal and the resulting impact and betterment on baseline flows across a series of rainfall events including allowance for climate change.
- High level cost estimate of potential construction.
Throughout the design process, the team utilised a range of tools for collaborative and efficient iterative design process. This included:
- SCALGO’s canvas tool, allowing consultants to interact and add ideas and observations spatially on the site.
- The creation of an intervention tool kit to set out and communicate the types of NFM interventions which may be proposed across the site.
- Continuous conversations between hydraulic engineers and landscape designers feeding the design work into the modelling and vice versa.
The final design included a site-wide strategy in the form of a series of interconnected NFM interventions split into four opportunity areas, allowing the phased implementation of the scheme. Land management changes were also proposed to areas across the site that are inline with current landscape plans of the National Trust and help to improve the site’s hydrological outcomes alongside the NFM strategy.
A 2D hydrological model of the scheme was created in InfoDrainage and produced flood maps as well as a table of reduced runoff with associated graphs of the NFM scheme/land management changes across a range of rainfall events. These outputs will support the National Trust in the next phases of the project in securing funding, planning approvals and undertaking detail design for construction of the strategy.
