Predicting the microbial risk in flooded london dwellings using microbial, hygrothermal, and gis modelling

With a changing climate, London is expected to experience more frequent periods of intense rainfall and tidal surges, which will lead to an increase in the risk of flooding. Floodwater may deposit harmful microorganisms on building surfaces, while damp indoor environments in flooded dwellings can support the growth of microorganisms including mould, bacteria, and protozoa. This thesis investigates possible flood-borne and damp-related pathogens in flooded London dwellings, and the potential duration of microbial contamination risk following a flood event. Microbiological laboratory work and models are used to characterise microbial risk within flooded dwellings. Dwelling archetypes representative of the London housing stock are developed and hygrothermal simulation techniques used to model the flooding and drying behaviour of the archetypes under different scenarios in order to predict the duration of damp and microbial risk inside typical dwellings. The results of the combined biological and hygrothermal models are mapped alongside existing flood risk maps in order to predict areas in London susceptible to long-term microbial risk or prolonged displacement following a flood. Highlights of the research findings include the following (i) The persistence of bacterial contaminants on flooded materials is related to the type of floodwater, the drying conditions including temperature and drying rate, and the material drying characteristics, ii) Different dwellings in London have different drying behaviours due to their built form and dominant wall types, with modern purpose-built flats the most prone to long-term damp and microbial risk following a flood event, (iii) The flood height, external weather, and internal conditions including heating and ventilation can have a major impact on the length of time a dwelling will remain at risk of microbial contamination, and (iv) The concentration of properties vulnerable to long-term microbial exposure following major flood events is highest in areas of South and East London, particularly Southwark.