Streamlining UK Flood Hydrology: A New Era with Hydrology+
- Alastair Sheppard
- May 30, 2024
- 3 min read
Updated: Feb 20
Flood estimation methods can be broadly divided into two main approaches. The first is the statistical method, which uses decades of observed river flow records to estimate peak flows for extreme events. The second is conceptual catchment modelling (rainfall-runoff), which derives design flood hydrographs from estimates of extreme rainfall. These methods are often combined to leverage each other’s strengths.
Evolution of Flood Estimation Techniques
Since the publication of the Flood Studies Report (NERC, 1975), the FSR techniques have become popular among the hydrology community for deriving flood hydrology for UK and Irish catchments. With the advent of more hydrometric data and advanced computing tools, the FSR methods were enhanced by various new research, including the IH124 method.
The Flood Estimation Handbook (Institute of Hydrology, 1999) introduced the FEH method, which replaced the FSR method. The FEH rainfall-runoff method was an extension and improvement of the original FSR method, later replaced by the Revitalised Flood Hydrograph (ReFH1 and currently ReFH2) for deriving T-year event peak flows and hydrographs. Many older methods continue to be used for niche applications such as reservoir safety.
Industry Standard for Deriving Flood Hydrology in the UK
The current UK industry practice for deriving flood hydrology involves applying the FEH methodology using the WINFAP and ReFH2 hydrology software packages developed by Wallingford HydroSolutions. These solutions are approved by the Environment Agency, the Scottish Environment Protection Agency, Natural Resources Wales, and the Department for Infrastructure Northern Ireland.
According to the Environment Agency Flood Estimation Guidelines (2022), the latest version of WINFAP has replaced most previous peak flow estimation methods for ungauged sites. Similarly, the latest version of the Revitalised Flood Hydrograph (ReFH2) method has replaced the original 1999 FEH rainfall-runoff method for most applications.
WINFAP can undertake statistical analysis for both gauged catchments (single site and enhanced single site analysis using AMAX data) and ungauged catchments (pooling group analysis using peak flow dataset at UK gauges and FEH catchment descriptors). ReFH2 can derive both peak flow estimates and flood hydrographs using FEH catchment descriptors and the latest rainfall data, available within the FEH web service.
ReFH2 is recommended within the CIRIA SuDS Manual for estimating greenfield runoff rates and volumes using the rural model, replacing many older methods. It is also recommended for estimating post-development runoff rates and volumes for simple developments using urban modelling capabilities. Brownfield runoff rates for developments are also modelled using ReFH2.
Accelerating Project Delivery with Hydrology+
Flood Modeller has revolutionised project delivery by directly integrating WINFAP and ReFH2 into Hydrology+. This integration brings advanced workflows, tools, and automation to both hydrologists and hydraulic modellers.
Hydrology+ digitises the hydrological analysis workflow, ensuring consistency, repeatability, and easy adoption of the latest UK hydrological methods. It covers all stages of hydrological analysis, including data collection and visualisation, catchment schematisation, WINFAP and ReFH2 analysis, reconciliation of methods, application of hydrology, and reporting.
Organisations already using WINFAP and ReFH2 can seamlessly integrate their existing licences with Hydrology+. Those looking to undertake flood risk assessments or transition from drainage design software can derive greenfield/brownfield discharge rates and volumes using the latest tools. The integration with Hydrology+ enables rapid updates of methods within a structured workflow.
Key Features of Hydrology+
Access to the Latest Datasets: Hydrology+ provides access to the latest datasets, including FEH Online, Environment Agency gauge data, and the UKCEH National River Flow Archive (NRFA), all within Flood Modeller. This ensures you are using the most up-to-date data while simplifying access.
Integrated WINFAP and ReFH2 Workflows: Fully integrated workflows provide access to the most current methods and tools, including FEH22 rainfall and the latest climate change uplifts.
Direct Application to Models: Hydrology+ allows for the direct application of hydrology to both 1D and 2D models, enabling rapid assessment of flood risk and eliminating the need for reprocessing hydrological analysis.
Automated Reporting: Automated reporting, aligned with Environment Agency requirements, allows for the automatic generation of hydrology deliverables, saving time and reducing human error
For further information, visit the Hydrology+ webpage.
