Urban Vulnerability Assessment Population Estimation More Look at ‘RA Elective Element’ of ITC

Population Projection Needed for planning purposes Length of time in the future for projections Short term (up to 10 years) Long term (up to 50 years) Both depend on past records

Population Forecasting Model to estimate population Direct Method Indirect Methods

Direct Method

Methods for Estimation Graphical methods Extrapolation Least squares regression Mathematical methods Assumes that population growth follows a mathematical relationship

Population Growth Population growth is generally considered to be exponential P=P0ert where: P = future size of the population at time t P0 = current size of the population t = number of years for the extrapolation r = assumed constant rate for each of the t years Reference: class notes of Dr. deMonsabert (GMU)

How to Calculate r? The growth rate (r) is usually expressed as a fraction of the increase in population per year Growth rate is also defined by the following equation: r=(b-d)+(i-e) where: b = birth rate d = death rate i = immigration rate e = emigration rate net migration = i-e Natural increase of population = b - d Net migration= the rate with which people moving into a region minus the rate with which people leaving that region

Example: The 2010 population in a town is surveyed and determined to be 50,000. What would you predict the population to be in the years 2020 if birth rate is 40 persons / 1000 people (or 4 %), death rate 15 persons / 1000 and net migration is 10 persons / 1000 people?

Doubling Time Double time represents the length of time for the population to double in size when growing with a constant growth rate (r) Tdb =70/r where: Tdb = the doubling time r = the constant growth rate in %

Indirect Method Population estimate derived from: Household counts and occupancy rate School registered children Residential area with population density Roof Area Method Total Population = Total roof area of all buildings/average roof area per person What about informal settlements? Sample survey can be done to calculate population density or average roof area per person. Number of occupants vs. roof area can be plotted and trend line can be used for unplanned residential area.

Source of Data Existing registers: Census data, cadastral data, taxation data Existing maps: Topo maps, cadastral map Field surveys Satellite images/aerial photographs DEM and DSM (deriving building heights)

Statistics Characteristics Number of inhabitants Densities Age composition Gender distribution Etc.

Dynamic Characteristics Population is dynamic in space and time Activity pattern Distribution in space Distribution in time

Daily Human Activities Source: Dr. Richard Sliuzas, ITC Similar charts for ‘Presence of school children’ and ‘presence of house wives’ during day for different days of a week. Hourly presence of people = # of house holds* (persons) + # of shops* (persons) +# of other units *(persons)