Project Details
Client: Sytner Group Limited & Rodgers Leask Limited
Categories: Hydraulic Modelling
When: March - May 2024
Location: Syston, UK
Edenvale Young were commissioned by Rogers Leask Limited, on behalf of Sytner Group Limited, to undertake hydraulic modelling to support the Ordinary Watercourse Consent (OWC) for the diversion of a culverted Ordinary Watercourse for a proposed development at Rayns Way in Syston.
The site boundary encompasses an existing building with ground level parking. Currently, a culverted Ordinary Watercourse runs through the site, and due to proposed development, the watercourse needed diverting.
The objective of the hydraulic modelling was to assess any third-party flood impacts as a result of the proposed diversion and assess alternative designs if required. The objective was achieved by building a direct rainfall model for the development site catchment and incorporating the proposed culvert diversion into the flood model.
Model Build
The direct rainfall model was built using TUFLOW. The model boundary was generated based on the site’s catchment, delineated from LiDAR data (obtained from DEFRA ). The catchment’s material roughness’ were based off OS mapping and soils information was informed by soil mapping from ISRIC World Soil Information. The design rainfall hydrology was derived from the ReFH2 model (version 2.3) with the recommended storm duration of 4hrs.
The whole catchment direct rainfall model is mostly 2D, however the pipe network local to the site was added in 1D ESTRY. The baseline model represents the current site, with the existing culverted watercourse, and the post-development model incorporated the proposed culvert diversion.
The results from the direct rainfall model showed that the majority of the catchment, including all vulnerable third party receptors, saw no change in flood depths as a result of the proposed diversion. The model build and results were documented in a report to support the successful Ordinary Watercourse Consent.
The summary of this study presents that the proposed Ordinary Watercourse diversion does not cause any issues with respect to flood risk and is considered an appropriate design solution.
The max depth results from the baseline and “post-development” scenario are shown below.
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