National Exposure Information System

How do we model exposure?

The National Exposure Information System (NEXIS) is a Geoscience Australia capability designed to provide comprehensive and nationally consistent exposure information to enable users to understand the elements at risk. Exposure information is produced by sourcing the best publicly available information, statistics, spatial and survey data about buildings, demographics, community infrastructure and agricultural commodities.

Buildings and structures are classified into overarching categories of land use: Residential, Commercial, Industrial, Institutions (public), Infrastructure and Agriculture to aid data collection and synthesis from a range of sources.

Sometimes datasets only cover a specific building attribute or region of Australia and to ensure national consistency spatial and statistical modelling is used to populate features with unknown attributes. The building type (e.g. house or apartment), number of occupants, building age, structure (e.g. wall and roof type, number of storeys), household income and other household demographic indicators, building construction and replacement costs are derived from disaggregating regional information and statistical calculations. For this reason, NEXIS information is not intended for operational purposes at the building or individual feature level but provides aggregated exposure information at existing administrative or geographic boundaries.

Residential exposure

The variables required to assess the risk for residential areas are primarily spatial, structural (construction year, wall and roof materials, building size), economic (construction and replacement cost value) and demographic (population and social vulnerability indicators).

In the absence of specific residential information, spatial and statistical modelling has been used to derive information required for risk assessments.

Spatial location of a building: Where the actual location of a building is not available from authoritative source data, spatial modelling of the Geocoded National Address File (GNAF), cadastral and land use data is used to derive a building location as well as the number of dwellings at each building location.

Structural information: Where actual building structure information is not available, proxies are created to fill any gaps. For example the Tasmanian Valuer-General data contains information on residential roof and wall materials used in the construction. This information is first applied to the actual building it relates to and then used to create statistics from which a standard range of building types can be generated. The building types are applied to individual building gaps in similar regions across Australia.

Regions: For each state and territory defined homogeneous areas based on Settlement (10 classes) and Wind (5 classes) classifications have been created to inform construction types, materials and costs which can vary between regions. For example, the types of construction, costs and transport for materials and labour will differ between isolated rural towns in comparison to inner CBD suburbs. Defining homogenous areas enables the ability to apply proxies to similar regions in the absence of building specific data.

This image is a map of Melbourne CBD extending north by 420 kilometres. The map is colour coded to show homogenous populated areas based on the ABS Urban Centres and Localities dataset coupled with built environment engineering knowledge forming 10 colour coded Settlement Type classes

Settlement Type

Map of Australia showing five wind region classes colour coded

Wind Region











Demographic and Social Vulnerability: Australian Bureau of Statistics (ABS) Census provides demographic statistics at SA1 or SA2 level and dwelling type where available for census periods. This information is applied to the NEXIS building and dwelling location.

Building Replacement Value: The cost to rebuild the same type and sized building with the same materials using current standards at current prices; it does not include market value and land value. Building cost factors are sourced from quantity surveyors and can be adjusted quarterly utilising Rawlinsons quarterly pricing indices.

Residential buildings contents value: The contents value is derived based on a percentage of the replacement value adjusted depending on the dwelling income classification: Low income 30%, Middle income 40%, High income 50%.

Population exposure

A population density product has been modelled utilising the NEXIS residential dwelling population estimate (see the data dictionary below) at the building location using a nearest neighbour analysis. Population density is calculated by the number of people within 10sqkm, 5sqkm, 1sqkm, 500sqm and 100sqm. Population density is only available as a web map service and has been classified into defined population categories with fixed scale ranges. This product provides a population density distribution raster dataset across Australia.

Commercial and industrial exposure

The variables required to assess the risk for the business sector are primarily spatial, structural (construction year, wall and roof materials, building size, number of storeys, basements), economic (construction and replacement cost value) business type, operations (employees and turnover).

Many of the processes used to model residential buildings are the same for commercial and industrial buildings. The differences in the processing are as follows:

Structural information: Where actual building structure information is not available, proxies are created to fill these gaps, for example surveys undertaken by Geoscience Australia in industrial zones gather data on construction type and materials used in the structure and facade. This information is first applied to the actual building it relates to, and then used to create statistics from which a standard range of building types can be generated. The building types are applied to individual building gaps in similar regions across Australia.

Commercial and Industrial buildings contents value: Due to the variety and complexity of business and industrial types NEXIS does not capture or derive contents value for commercial and Industrial buildings.

Business type/ operation: Exposure information relation to business type, number of employees or turnover is not currently available in NEXIS.

Agriculture exposure

Agriculture exposure information has been derived using the ABS Total Value of Agricultural Commodities Produced (VACP) applied to cadastral parcels in areas identified as suitable for agricultural production. Agricultural production areas were defined by the areas not classified as Commercial, Crossing, Desert, Easement, Education, Hospital/Medical, Industrial, Mining, Native Vegetation, Parkland, Prohibited Areas, Rail, Reserves, Residential, Road, Transport, Water. VACP value and commodity presence at the SA1 level was applied at cadastre parcel level but are available aggregated to SA1 or LGA. Agricultural commodity list and value estimates are provided for the Year ending 30 June 2011 as well as the 2011-12 and 2012-13 inter-censual periods.

Institutions exposure

Institutions or public buildings include education, health and welfare, emergency services, government, cultural buildings and recreational facilities. Institution exposure information currently consists of counts of some of these institutions by type. The location and institution type information is from authoritative data sources and not derived or modelled. Future exposure information will include construction type and capacity information such as number of staff, beds, students and seating and replacement costs.  

Infrastructure exposure

Infrastructure includes transport (road, rail, stations, bridges, tunnels, ports and airports), communications (antennas, exchanges and towers), energy (fuel and power assets) water and waste facilities. Infrastructure exposure information currently consists of some of these sector types. The location and infrastructure type information is from authoritative data sources and not derived or modelled. Future exposure information will include construction type, capacity information such as kilowatts and litres/mega litres, and replacement costs.

Data dictionary

The NEXIS data dictionary contains a list of the attributes and how they are derived in its Building Exposure dataset. These include (but are not limited to) those data items listed below with a description.

Population estimate: Using the ABS Census 2011, the population estimate methodology takes into account:

  • the average population per occupied private dwelling structure type for each Statistical Area1 (SA1)
  • the proportion of unoccupied dwellings in the total dwelling stock by structure type
  • the ratio between the 2011 Estimated Resident Population (ERP)
  • the Census population counts and the number of NEXIS derived residential dwellings.

Dwelling: A dwelling is a structure intended to have people live in it i.e. house and flat.
Residential buildings: A building consisting of one or more dwelling units and the primary use is to house people.
Separate houses (SH): A residential house which is separated from other residential dwellings and does not share a common wall.
Semi-detached houses (SD): A residential dwelling sharing a common wall with another dwelling, having their own private grounds with no other dwellings above or below.
Flat or apartment building (F0): A residential apartment building up to two (2) storeys.
Flat or apartment building (F3): A residential apartment building with three (3) storeys.
Flat or apartment building (F4): A residential apartment building with four (4) or more storeys.
Wall type classifications: concrete masonry, cavity and solid masonry, veneer masonry, precast concrete, timber, metal sheeting, fibre cement, mud brick or rammed earth and synthetic.
Roof type classifications: tile, metal sheeting, concrete, fibre cement, imitation tile and synthetic.
Structure value: is the cost to rebuild the existing structure (size and construction material) at current building standards at the current costs. Source: Altus Group Cost Management Pty Ltd, 2010. Building Price Index Quarterly updates, Rawlinsons Australian Construction Handbook, 32 edition, edited by Rawlinsons Quantity Surveyors and Construction Cost Consultants, Rawlhouse Publishing, Perth, Western Australia.
Contents value: is calculated as a proportion of the replacement cost, adjusted for depending on the gross income classification: Low income 30%, Middle income 40%, High income 50%.
Footprint: Area of the building footprints calculated in metres.
Floor area: Area of the total building (footprint x number of storeys) calculated in metres.
Gross household income: Nil, low ($1-$599), middle ($600-$1999) or high (greater than $2000) gross household income: For each dwelling type (SH, SD, F0, F3 and F4), a percentage is applied to calculate if that dwelling has a Nil, Low, Medium or High gross household weekly income as a proportion of all dwellings of that type. Dwellings with a negative gross household income are included in the Nil category. The low income household is determined by using the OECD definition of half the national median. In 2011 the national median was $1234/week, which gives a low income measure of $617/week. This has been adjusted to $600 because it is the nearest category in the Census data. High income is set to $2000/week, as this category reflects the top deciles nationally. ABS Census 2011.
Equivalised household income: For each dwelling type (SH, SD, F0, F3 and F4), a percentage is applied to calculate if that dwelling has Nil, Low, Medium, or High equivalised total household income as a proportion of all dwellings of that type. Dwellings with a negative equivalised total household income are included in the Nil category. ABS Census 2011. Equivalised total household income is total income adjusted by the application of an equivalence scale to facilitate comparison of income levels between households of differing size and composition. An ABS-modified OECD equivalence scale is used where 1 point is allocated to the first adult, 0.5 points to every subsequent adult and 0.3 for every child under 15. Equivalised total household income can be viewed as an indicator of the economic resources available to a standardised household. For a lone person household it is equal to household income. For a household comprising more than one person, it is an indicator of the household income that would be needed by a lone person household to enjoy the same level of economic wellbeing.
Residential tenure: refers to the financial arrangements under which someone has the right to live in a house or apartment. Owned - Owned outright or owned with a mortgage.
Rented - Rented from a real estate agent or direct from owner.
Rented Public Housing - Rented from a State/Territory housing authority or rented from a co-operative, community or church group.
Other Tenure Types - Rented from a person not in the same household, occupied rent-free, occupied under a life tenure system and all other tenure types, as a proportion of all dwellings of that type. ABS Census 2011.
Do not have access to a motor vehicle: households which do not have access to a registered motor vehicle at or near the dwelling (on Census night) as a proportion of all dwellings of that type. ABS Census 2011.
Aged less than 5 years: household with one or more persons aged between 0 and 4 years as a proportion of all dwellings of that type. ABS Census 2011.
Aged 65 years and over: household with all persons aged 65 years and over as a proportion of all dwellings of that type. ABS Census 2011.
One parent families: household containing a one parent family with children under the age of 15 as a proportion of all dwellings of that type. ABS Census 2011.
Persons needing assistance with core activities: household where one or more persons needs assistance with a core activity as a proportion of all dwellings of that type. People with a profound or severe disability are defined as those people needing help or assistance in one or more of the three core activity areas of self-care, mobility and communication, because of a disability, long term health condition (lasting six months or more) or old age. ABS Census 2011.
No English: household where all persons have low English comprehension as a proportion of all dwellings of that type. ABS Census 2011.
No year 12 education: household where all persons highest educational attainment is year 11 or below as a proportion of all dwellings of that type. Includes households where all persons have no educational attainment. ABS Census 2011.
Voluntary work: household where one or more persons undertook voluntary work as a proportion of all dwellings of that type. Comprises people who spent time doing unpaid voluntary work through an organisation or group, in the twelve months prior to Census night. It excludes work done as part of paid employment, if the main reason is to qualify for a Government benefit or if the work was done as part of a family business. ABS Census 2011.
Moved one year: household where all persons lived in a different SA1 in 2010 to the SA1 they lived in on Census night as a proportion of all dwellings of that type. ABS census 2011.
Moved 5 years: household where all persons lived in a different SA1 in 2006 to the SA1 they lived in on Census night as a proportion of all dwellings of that type. ABS census 2011.

Commerical building construction types

Number of Storeys

Construction Type

Description

1 - 3
Storeys

13_C_O

Concrete Frame and/or Shear wall; Other Exterior Walls

13_C_URM

Concrete Frame and/or Shear wall; URM Exterior Walls

13_LBM_C

Load Bearing Masonry; Concrete Column Floors

13_LBM_S

Load Bearing Masonry; Steal Beams and Columns

13_LBM_T

Load Bearing Masonry; Timber Column Floors

13_S_O

Steel Frame with/without Concrete Shear Core; Other Exterior Walls

13_S_URM

Steel Frame with/without Concrete Shear Core; URM Exterior Walls

4 - 7
Storeys

47_C_O

Concrete Frame and/or Shear wall; Other Exterior Walls

47_C_URM

Concrete Frame and/or Shear wall; URM Exterior Walls

47_LBM_C

Load Bearing Masonry; Concrete Column Floors

47_LBM_S

Load Bearing Masonry; Steal Beams and Columns

47_LBM_T

Load Bearing Masonry; Timer Column Floors

47_S_O

Steel Frame with/without Concrete Shear Core; Other Exterior Walls

47_S_URM

Steel Frame with/without Concrete Shear Core; URM Exterior Walls

8 - 35
Storeys

835_C

Concrete Frame and/or Shear wall

835_S

Steel Frame with/without Concrete Shear Core

36+
Storeys

36_C

Concrete Frame and/or Shear wall

36_S

Steel Frame with/without Concrete Shear Core



Industrial building construction types

Number of Storeys

Construction Type

Description

Single
Storey

ISS_URM_S

URM Walls; Supporting Steel Roof

ISS_URM_PS

URM; Steel Portal Frame and Roof

ISS_RM_S

RM; Supporting Steel Roof

ISS_SS_S

Steel Frame; Steel Clad Walls and Roof

ISS_SSURM_S

Steel Frame; URM/Steel Clad Walls; Steel Roof

ISS_SSPC_S

Steel Frame; Precast/Steel Clad Walls; Steel Roof

ISS_SPC_S

Small Panel; Precast Walls; Steel Portal Frame and Roof

ISS_PC_S

Large Panel; Precast Walls; Supporting Steel Roof

Double
 Storey

IDS_CSURM_S

Concrete First Floor; Steel Portal Above; URM walls; Steel Roof

IDS_CSPC_S

Concrete First Floor; Steel Portal Above; Precast Walls; Steel Roof

IDS_CURM_S

Concrete First Floor; URM Walls; Steel Roof

Single Storey with Basement Car Park Structure

ISSB_CSPC_S

Concrete Basement; Steel Portal Superstructure; Precast Walls

ISSB_SSS_S

Steel Frame; Concrete Pan Basement; Steel Superstructure