Exciting new research into flood frequency estimation in groundwater dominated catchments

Research, development and collaboration are at the heart of what we do at JBA. Our investment in these areas means we can provide clients with bespoke innovative solutions and incorporate the latest technical knowledge.

Background:

We were recently commissioned by the Environment Agency to complete a scoping study with the aim to identify challenges with flood frequency estimations in catchments where groundwater exerts a major influence on river flow. The report also proposed further work and research needed to address these challenges. JBA’s Head of Hydrology Duncan Faulkner was the lead on this research project.

Groundwater dominated catchments can be defined as those in which the river flow is dominated by contributions from groundwater e.g. baseflow. These catchments are mostly found in the South and East of England in areas of chalk, Jurassic limestone and Triassic sandstones.

Challenges:

The core of this report discusses some of the challenges of estimating flood frequency in the groundwater dominated catchment areas. The six challenges that were found to be inter-related include:

· Difficulty defining the contributing catchment area

· Other changes in processes between smaller and larger floods

· Ephemeral streams

· Annual maximum flows that are not floods

· Non-stationarity

· Long-lasting floods

These challenges are demonstrated through the use of case studies on six groundwater dominated rivers.

Findings:

The results of the report found that the methods of the Flood Estimation Handbook (FEH) show some evidence of higher uncertainty in groundwater dominated catchments compared with rainfall dominated catchments. Due to these results, a list of suggestions was produced to provide improvements to FEH and alternative methods. We also made some recommendations for current practice and future research.

This has been one of the most interesting and enjoyable projects I’ve worked on in a while. I relished the opportunity to revisit the fascinating topic of interactions between rivers and the mysterious underground realm of groundwater, after contributing to a similar project back in the 1990s.

Duncan Faulkner, Head of Hydrology

You can read the full report here: Review of flood frequency estimation in groundwater dominated catchments.

Want to know more?

For more information on our work in Water Resources Management, click here.



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