Modelling flooding due to runoff from spoil heaps during heavy rainfall

Flash floods generated by runoff from abandoned spoil heaps have posed great risks to neighbouring areas but there has been little study on the process, so it is difficult to evaluate the effectiveness of runoff retention or detention measures. These events are likely to become more frequent in a future climate change scenario. To provide a means by which interested parties can study such events, including methods of mitigation, a computer modelling approach is proposed using free open-source software. Unlike conventional tools that solve the shallow water equations, the software tool uses a cellular automata approach to reduce the computational overhead. It is also easy to use so it is suitable for use by practitioners who are not hydrology experts. The method is illustrated by modelling a historical flood in the UK involving spoil heap runoff. Good correlation was observed between the characteristics of the actual and simulated flood event.