Integrated Modelling for Midleton Flood Relief Scheme, Ireland
- Alastair Sheppard
- Sep 2, 2024
- 3 min read
Updated: Mar 11
What our customers say:
“The mechanisms of flooding in Midleton are both varied and complex. The use of Flood Modeller and TUFLOW proved invaluable to the project and allowed flood risk to be assessed with a high degree of confidence. It also allowed the technical viability of various options to be evaluated in detail as part of the overall optioneering process by reconfiguring the existing scenario model.”
Kevin Barry, Senior Engineer, Arup
Arup was commissioned by Cork County Council to design a comprehensive flood relief scheme for Midleton, Co. Cork, Ireland to mitigate the town’s long-standing flooding issues. This scheme will implement flood alleviation measures to protect against fluvial, tidal, pluvial, and groundwater flooding, achieving a target standard of protection of 1% Annual Exceedance Probability (AEP) for fluvial flooding and 0.5% AEP for tidal flooding.
As part of the project, Arup developed an integrated 1D-2D Flood Modeller-TUFLOW model for the primary watercourses in Midleton. The Flood Modeller component spans approximately 25km and incorporates over 50 structures, including two intricate Mill Races running parallel to the main watercourses. The TUFLOW model covers an area of around 7km² with a fixed grid resolution of 2 meters.
The coupled model was calibrated and validated against three distinct high flow events of varying magnitudes: two in-bank high flow events from 2018, measured by temporary gauges deployed in the town, and a significant out-of-bank flood event from December 2015 that impacted large areas of Midleton. The model achieved a very good match with both measured and anecdotal data, demonstrating its robustness and accuracy in replicating the complex flooding mechanisms across Midleton.
After confirming the model’s accuracy, it was used to identify flood-prone areas in Midleton by simulating a range of Annual Exceedance Probability (AEP) events for various climate epochs. The key finding was that large areas of the town are at risk from both fluvial and tidal flooding. Approximately 463 residential and 188 commercial properties are at risk in a combined 1% fluvial AEP / 0.5% tidal AEP event. Flood extent maps were created for both fluvial and tidal scenarios to highlight all at-risk areas. Additionally, maps depicting groundwater and pluvial flood risks were produced.
Key Facts
A flood relief scheme designed to protect against fluvial, tidal, pluvial, and groundwater flooding.
A fully integrated 1D-2D Flood Modeller-TUFLOW model was developed.
Modelling indicated that extensive areas of the town are at risk from both fluvial and tidal flooding.
Several viable options were developed and subjected to a detailed appraisal.
A number of viable options were developed which were subject to a detailed appraisal including (1) a multi-criteria analysis to evaluate the performance of each option in terms of predefined technical, environmental, social and economic objectives, (2) cost-benefit analysis to assess the overall monetary value of each option over the lifetime of the scheme, (3) detailed consultation with the public and landowners, (4) climate change adaptation, (5) consideration of wider client objectives and other infrastructure projects currently being developed in the area. An emerging preferred option for the scheme was selected. The preferred scheme was presented to the public at the project’s third public participation day in July 2022.
A comprehensive range of potential flood alleviation options were explored during the study. The technically viable options were modelled by reconfiguring the existing scenario model to represent each option, which included various combinations of engineering measures such as direct defences, upstream storage, groundwater cut-offs, over-pumping, conveyance improvements, and flood diversion culverts.
Several viable options were developed and subjected to a detailed appraisal process, which included:
A multi-criteria analysis to evaluate the performance of each option against predefined technical, environmental, social, and economic objectives.
A cost-benefit analysis to assess the overall monetary value of each option over the scheme’s lifetime.
Detailed consultations with the public and landowners.
Consideration of climate change adaptation.
Alignment with broader client objectives and other infrastructure projects in the area.
An emerging preferred option for the scheme was selected and presented to the public during the project’s third public participation day in July 2022.
