Transcript Microbial Growth Models

GIS, Building Simulation, and Microbes in Flood Impact Studies
Jonathon Taylor1,2, Ka Man Lai1, Michael Davies2
1Department
of Civil, Environmental, and Geomatic Engineering, UCL
2The Bartlett School of Graduate Studies, UCL
Introduction
Data Analysis
UKCIP 2009 climate projections indicate that London will experience more
frequent extreme precipitation events, a rise in sea level, and more frequent
storm surges1. As a result, flooding is expected to occur more frequently in
London.
The English Housing Condition Survey database contains information on the
age, structure, and construction type of different buildings. There is a
correlation between construction type, materials, and age based on the
building standards in force at the time of construction.
Spatial information has been widely used in flood mapping and health
research, but the inclusion of building stock models can add additional
insights. Wall and floor types vary according to building age, and computer
simulations can be performed to model how they absorb and desorb water.
The amount and duration of water activity in the building envelope impacts
the post-flood microbial growth, and results in potential health problems.
This research aims to increase the understanding of the health implications
of flooding in London by combining GIS, building physics, and microbial
models.
The behaviour of moisture levels inside buildings can be simulated using Heat
Air and Moisture (HAM) models, allowing post- flood drying times for different
walls and floors under current and future climate scenarios to be modelled.
Wall Type
Initial 1 Month
3 Months
6 Months
Single Brick
Masonry
Data Sources
Insulated
Brick Cavity
The research area of central London was chosen because it is a flood
vulnerable area with a diverse building stock and good data coverage. The
area includes 250,000 dwellings, with 70,000 homes and 470,000
inhabitants at risk of flooding.
Different buildings take different amounts of time to dry out. Previous flooding
research has been limited to constructing physical walls, and so a wide range
of drying scenarios have not been tested. HAM simulation allows for a wide
range of floors, wall and climate scenarios to be easily simulated.
Figure 3. Relative Drying times after a 20cm winter flood in
current climatic conditions
Figure 1. Research area of London with an Environment Agency 1 in 200 flood map
Microbial Growth Models
Ordnance Survey Mastermap building shapefiles, address points and age
and structural information from Cities Revealed allowed for conclusions to be
drawn regarding the construction of the buildings.
Mould, bacteria and protozoa have all been found on damp and flooded walls.
Their survival is dependent on the temperature and the water activity in the
walls, the species, and the wall materials. Models exist that describe mould
survival on building surfaces, and can be expanded to include other floodborne microbes.
Figure 4. Isopleth model describing Aspergillus germination and growth2.
Implications
Figure 2. Building age data can be used to estimate the materials and construction of
walls and floors
The data was supplemented with insulation data from the Home Energy
Efficiency database, and validated using census data over larger areas.
LiDAR height data allowed the depth of flooding in individual buildings to be
calculated.
By combining multidisciplinary components together, we can get a holistic
picture of the potential health implications of flooding at a population level
across different spatial and temporal scales. Information on the variations in
damp buildings and their ability to support microbial growth will be mapped
out across London. The outputs from this study will include: an environmental
exposure model which can be used to assess health implications for
occupants; a better idea what microbiological hazards will exist inside drying
buildings over time; and guidelines for flooded home remediation.
References
1UKCIP,
Climate Change Projections Version 2, 2009.
2Sedlbauer, K. Prediction of mould fungus formation on the surface of and
inside building components, 2002.