Current PhD Projects:

Previous PhD Projects:

Hydrological Performance Evolution of Extensive Green Roof Systems

The use of green roofs as a method of stormwater runoff control is relatively new within the UK. As a result of this a vast majority of the roofing systems can be thought of as 'young'. Most of the current research is conducted on purpose-built brand new green roof test rigs with limited exploration of ageing effects. Ageing processes within the roof have the potential to alter the roof's performance, but not just its hydrological performance. Existing studies explore the stabilising effect of roof age on plant growth and increasing biodiversity; hydrological performance has not been given the same attention yet it can often be the primary objective of the roof's design. 


The aim of the research is to determine the effects that ageing has on multiple aspects of the green roof, with emphasis on the changes within the substrate layer. These changes are to be determined using an array of techniques, including X-Ray Micro Tomography, an example of this can be seen in the video (Right). Changes within the substrate over time could lead to changes in the hydrological performance of green roofs, potentially reducing the benefits that were originally forecast during design, installation and initial monitoring.

The physical influences affecting a green roof's hydrologic response
Simon Poë
Green roofs can potentially form an integral part of any sustainable drainage strategy, particularly in urban areas. However, the relative scarcity of commercial hydrologic engineering software applications capable of including green roof contributions in the analysis is surely restricting the number of green roof installations within SUDS strategies.
This research aims to establish a physics-based approach that equates different soil-water contents, climatic boundary conditions and vegetation and substrate resistance factors to soil-water potential by:
  • Generating an empirical data set to enable analysis of hydrologic performance of different green roof configurations. 
  • Identifying water balance changes in roof configurations during wetting and drying cycles to underpin modelling of soil-water fluxes via algorithms.
  • Establishing the quantitative impact of each physical influence on water balance, equating it to a ψ value.
  • Developing a model that predicts green roof retention and detention by estimating soil-water fluxes in accordance with the θ-ψ relationship.
Simon's thesis can be viewed on WRRO.

Investigating the Planting Potential for Urban Rain Gardens: Plant Selection, Establishment and Performance
Jia Yuan
Jia's thesis can be viewed on WRRO


Additional Projects
  • Gianni Vesuviano, 2014, A two-stage runoff detention model for a green roof
  • Hartini Kasmin, 2010, Hydrological performance of green roofs

Other Projects:


Potential PhD Projects:

The research group welcomes applications from potential PhD students wishing to work on any aspect of green roof hydrological performance, as well as those interested in other vegetated SuDS, including rain gardens, stormwater planters and street trees. Most projects will include some experimental work and some model development work, for which an ability to use MATLAB (or at least a willingness to learn) would be a distinct advantage. Applications from Civil Engineering & Geography students are particularly welcome. The group does not have any funded PhD projects on offer at present, but there are scholarships available for applicants who can demonstrate strong research potential.

Sample potential project outlines can be found here.