Using Integrated 1D–2D Modelling to Reduce Flood Risk in Oxfordshire
- Jul 17
- 3 min read
Updated: Jul 20
“ Flood Modeller’s visualisation tools for 1D outputs are really helpful in exploring volumes spilling into overland flow paths without needing to run a full 1D-2D model.”
Matt Horritt, Independent Consultant, Horritt Consulting
Key Facts
Frequent Flooding: Oxfordshire village floods around every 10 years, with 50+ properties affected in 2024 due to limited culvert capacity.
1D–2D Flood Modeller Application: A linked 1D–2D model using the ADI solver captured culvert exceedance, surface flows and drainage interactions.
Efficient, Realistic Modelling: Despite complex linking challenges, the model runs quickly and closely matches observed 2024 flooding.
Informing Investment Decisions: Outputs assessed storage and culvert upgrade options and are now supporting the Environment Agency’s mitigation business case.
Understanding The Flooding Problem
South Oxfordshire District Council and Horritt Consulting have undertaken hydrological and hydraulic analysis using Flood Modeller to explore options for flood alleviation for a village in Oxfordshire. The village is subject to frequent flooding, approximately every 10 years or so; most recently, in 2024, significant flooding occurred with more than 50 properties affected. The main cause of this flooding is a lack of capacity in a culvert carrying a brook under the village, with excess water flowing over the surface along the original line of the watercourse.
Model Development and Approach
Jacobs’ Flood Modeller software has been used to build a 1D-2D model, with the 2D domain represented using the Flood Modeller ADI solver. The 2D model is linked to the 1D model at the culvert entrance, where the limited culvert capacity generates significant overland flows, and along the length of the culvert via drains and manholes.
Water is also allowed to drain back into the channel at the culvert outlet. A number of modelling challenges had to be overcome: instabilities in the 1D-2D link; coupling the culvert and 2D model to represent manholes; reconciling hydrological analysis with the known flood history. Some compromises were required, but these delivered a relatively quick-to-run model that represents the most important flooding mechanisms and matches the flooding observed in 2024.
Testing Flood Alleviation Options
The model has been used to explore a number of options for flood risk mitigation, comprising storage schemes in the upper catchment and upgraded culvert capacity. A 1D-only version of the model is also used to quickly explore options by measuring flow and volume at the spill located at the culvert entrance. Flood Modeller’s visualisation tools for 1D outputs are really helpful here for exploring volumes spilling into overland flow paths without needing to run a full 1D-2D model.
Key points for 1D -2D linking are at the culvert entrance (top) and at a number of drains connected to the culvert, which are represented as spill units and flow links.
Supporting Decision‑Making
2D outputs have been used to estimate depths at receptors and hence damages for the various options explored; these are now being used by the Environment Agency to support the business case for mitigation measures for the village.
Matt Horritt
Matt is an independent consultant with 30 years of experience in flood modelling and risk assessment in universities and industry. His work covers flood risk assessments for developers, local authorities and infrastructure owners, modelling for river restoration and fish passage works, and national-scale climate change and adaptation strategies.
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