Optimizing gully blocks to reduce flood discharge

David Milledge (NU), Caspar Hewett (NU), David Brown (EA)

 

Apply for this PhD here https://applyto.newcastle.ac.uk/ using application studentship code FLOOD249. Please contact Caspar Hewett (caspar.hewett@newcastle.ac.uk) if you have any questions about the application process. 

 

 

Rationale: 

Society faces big, interrelated challenges on biodiversity, regeneration of ecosystems impacted by atmospheric pollution, global climate change, carbon capture and storage, flooding and drought. In UK uplands there is widespread activity to mitigate these challenges using nature-based/inspired interventions: through revegetation, land use change and ditch/gully blocking, motivated by biodiversity improvement; carbon capture and flood management. Many types of intervention are being proposed, and even implemented, that alter the hydraulics of channels. However, there is limited understanding of how they work, how much impact they deliver and under what circumstances. In UK upland peat landscapes, the biodiversity and carbon capture components of interventions like gully blocking are established, but hydrological impact in terms of peak discharge attenuation and downstream flood risk reduction are not well understood. Are they doing what we want them to do? How could they be modified to improve their effectiveness? This project aims to answer some of these fundamental questions through detailed investigation of the relationship between water storage and discharge - the critical relationship in defining the ability of a feature to attenuate flow, to hold storm water, and to partition peak flow into storage reducing the downstream peak discharge.

 

Methodology: 

This project will use field data, experimental work and modelling to answer fundamental questions about the hydraulics and hydrological impact of gully blocking features. This combination of modelling informed by and tested against observations will help address questions related to the effectiveness of existing designs and establish how to improve future designs. The project will (1) utilise rich observed data from a before-after-control-impact (BACI) study of a set of ~10 gullies in the South Pennine peat that have had different interventions installed and monitored[2]. (2) examine a variety of feature designs under controlled conditions in the Vedrana Kutija flume, which has a wide array of sensors to measure flow hydraulics at multiple locations at high space and time resolutions[3]. The flume dimensions facilitate testing features at almost full scale, helping to avoid the well-known scaling problems associated with physical modelling. (3) explore the parameter space further using hydrodynamic models tested against field and lab observations[3], enabling us to identify the appropriate physical representation, both in terms of the amount of complexity required and where that complexity is focused. New tools will be developed to drive feature design– particularly gully blocks and leaky barriers, both as individual features and as sets.

 

Location: 
Newcastle University
Background Reading: 

[1] Hill, B., Liang, Q., Bosher, L., Chen, H., & Nicholson, A. (2023). A systematic review of natural flood management modelling: Approaches, limitations, and potential solutions. Journal of Flood Risk Management, 16(3), e12899. Doi:10.1111/jfr3.12899

[2] Edokpa, D., Milledge, D., Allott, T., Holden, J., Shuttleworth, E., Kay, M., Johnston, A., Millin-Chalabi, G., Scott-Campbell, M., Chandler, D. and Freestone, J., 2022. Rainfall intensity and catchment size control storm runoff in a gullied blanket peatland. Journal of Hydrology, 609, p.127688.

[3] Leakey, S., Hewett, C.J., Glenis, V. and Quinn, P.F., 2022. Investigating the behaviour of leaky barriers with flume experiments and 3D modelling. In Advances in Hydroinformatics: Models for Complex and Global Water Issues—Practices and Expectations (pp. 965-978). Singapore: Springer Nature Singapore.