A Bayesian approach to complex land use change modelling

The UK is currently facing a housing shortage and the government plan is to increase house building to a rate of 300,000 per year in the mid-2020s. This is largely supported through policy instruments related to improving access to personal finance and reducing planning barriers. According to the government, over 40 per cent of local planning authorities do not have a plan that meets the projected growth in households in their area. Against this backdrop of announced substantial, poorly understood and more liberally regulated land use change, there is a clear need to understand possible patterns of future urban growth.

There exist computational models that take economic and demographic forecasts and use these to explore possible trajectories of land use change. A particular family of such models are Cellular Automata (CA) land use models; these models are complex in a mathematical sense as they represent the chaotic and spatially uneven processes by which cities and towns can grow. A major hurdle preventing the widespread use of these models is that the better performing models are calibrated based on 'expert judgement'. This reliance on manual intervention is not only resource intensive but also casts a shadow on the objective reliability of model results.

In this project we will investigate the use of a statistical technique of Approximate Bayesian Computation to automatically calibrate CA land use models. We aim to deliver a proof-of-concept demonstrating the methods on a CA model that is stripped down to its fundamental essentials, and applied to a variety of UK and European urban areas. A further advantage of the Bayesian approach is that it will not just give the best-fitting set of parameters, but also the associated uncertainty. This will allow analysts to use the model to arrive to support decisions with confidence based on a range of possible outcomes and their likelihood.

The project will allow the characteristics of urban growth across a number of European functional urban areas to be compared by estimating land use change models. This is of immediate policy relevance as it provides insight into how patterns of change could have been different and what future trajectories are possible, in addition to the historical trends. The UK is currently facing a housing shortage and the government plan is to increase house building to a rate of 300,000 per year by the mid-2020s. This is largely supported through policy instruments related to relaxing spatial planning restrictions and improving access to personal finance. According to the government over 40% of local planning authorities do not have a plan that meets the projected growth in households in their area. Consequently, it is anticipated that local authorities would be interested in tools that help foresee and manage urban growth, against this backdrop of announced substantial, poorly understood and more liberally regulated land use change.

The project aims to deliver a proof-of-concept, and further research and development will be necessary to deliver that impact to its fullest. Our actions supporting the pathways to impact are directed at facilitating uptake in research and development. The project can have a positive impact on the future direction of land use change research by demonstrating an overall approach to evidence based complex land use change modelling, and by making the composite elements of that approach widely available in an accessible form. This will be facilitated by sharing the source code and scripts of the full procedure in open source on the Github website which is the globally leading website for open source code sharing. It can reach professional users beyond academia, including analysts and consultants in the area of spatial planning and policy. By sharing the project outcomes in this manner, the foundation and platform for further dissemination will be established
The expected impact outside of research and development is through the application of the methods in existing or new planning support systems (PSS). As the project is aiming for an integrated solution, there is also the possibility of developing the method into a new product to be managed by a commercial partner as the project does present a unique capability of giving objective insight in the range of possible trajectories of future land use change. We will under the current bid develop communication material (PowerPoint slides, brochure, poster) highlighting the potential application of the developed methods rather than the underlying technical innovation. This will be directed at existing partners active in land management, such as local authorities, and national infrastructure operators and facilitate a discussion with them about possible future directions and applications of this work.