NERC ONE Planet DTP
Detailed flood models are increasingly used to assess future flood risk in cities and catchments, and to design flood attenuation features including green infrastructure (GI) which reduce the amount of water entering drainage systems via infiltration, transpiration and storage. The advanced flood model CityCAT [1] developed at Newcastle represents surface flows, the effects of buildings and even pipe networks, but has only a very simple representation of sub-surface flows in soils. This is very limiting as (a) infiltration of rainfall into dry soils can reduce flood runoff and (b) sub-surface flows can cause saturation and reduced effectiveness of GI. This project therefore aims to develop and apply a coupled surface and groundwater model based on the 3D Richards equations for variably saturated flow for use in flood modelling for future climates, accounting for changed soil wetness and the use of GI. The Richards equations are usually solved using the finite difference (FD) method [2] or the finite element (FE) method [3]. The main problems with the existing solutions are: a) mass conservation especially when the pressure form is used or implicit schemes are used; and b) inability to model conditions changing from unsaturated to saturated with explicit schemes. This project will develop new solvers for the 3-D Richards equations based on modern finite volume numerical methods to address the main problems of the standard FD and FV solvers. The new solvers will then be used to extend the current vertical-only infiltration capability of the CityCAT model [1], and used in two key assessments. Firstly, the impacts of changing storm intensity and the effects of increased antecedent drying on flood risk in cities and small catchments. Secondly (linked to the National Green Infrastructure Facility), the limits of using GI for flood risk management in cities with groundwater sensitive locations, e.g. Newcastle where minewater rebound is affecting the groundwater levels and causing flooding.
A number of stakeholders will be interested in this project, including Newcastle’s Blue Green Learning Action Alliance, comprising Newcastle City Council, Northumbrian Water, Newcastle University, ARUP, Atkins, Tyne Rivers Trust and Northumberland Wildlife Trust, all of whom have signed a declaration to promote GI across Newcastle.
Key Research Gaps and Questions:
Hydrodynamic flood models of cities and catchments are crucial for assessing future flood risk and designing adaptations. They account well for flows on impermeable or saturated surfaces, but currently cannot adequately represent sub-surface flows or infiltration at the start of a storm. With climate change likely to bring drier soil conditions and more intense storms, it is now very important to be able to account for these important surface-groundwater interactions.
Prerequisites:
Some mathematical ability and experience with numerical methods is needed. Experience of model application is desirable; willingness to learn programming. For more information, please contact [Email Address Removed]
Continue with Facebook
