Understanding blockage formation in combined sewer networks

This paper documents a key part of the development of a risk analysis process that may be used as a tool to manage maintenance expenditure within the context of 'serviceability' to customers, the public and the environment. Against the background of poor availability of reliable data, the text outlines the basis of a methodology that can be used to model blockage likelihood in combined sewers with limited information and without the need for additional data gathering. Specifically, the work reported here relates primarily to research undertaken to better understand what network- and catchment-specific factors influence the formation of blockages that lead to flooding in combined and foul drainage systems. The role of each of these factors is considered in turn and the significance of their impact is estimated.