Publication - Research and analysis

Mapping flood disadvantage in Scotland 2015: report

Published: 23 Dec 2015
Environment and Forestry Directorate
Part of:
Environment and climate change

This research identifies and maps the neighbourhoods in Scotland that would be most disadvantaged by flooding.

Mapping flood disadvantage in Scotland 2015: report


Adaptive capacity

The ability of people to prepare for, respond to and recover after flooding, related mainly to their social and material situation.

Annual exceedance probability

Annual exceedance probability ( AEP) describes the probability of a flood of a given magnitude occurring in any given year. AEP is the inverse of the flood return period. For example, 3.3% AEP refers to a return period of 1 in 30 years.

Data zones

Compact areas with around 500-1,000 residents that contain households with similar social characteristics used by the Scottish Government for reporting social statistics, for example the census. There are 6505 data zones in Scotland.

Defended flood extent

The area that has been identified as potentially exposed to flooding, where the underlying models have included consideration of formal flood prevention schemes ( e.g. walls, embankments). Thus, defended flood extents cover smaller areas than undefended flood extents.

Direct indicator

An indicator that directly reflects the factor influencing social vulnerability to flooding, e.g. proportion of older people in the population

Exposure (enhanced)

One of the dimensions of vulnerability, which refers to the aspects of the physical environment (housing and presence of permeable surfaces), which accentuate or offset the severity of flood events.

Flood disadvantage

A situation when vulnerable neighbourhoods are exposed to flooding. In other words, disadvantage occurs where high social vulnerability to flooding spatially coincides with flood hazard-exposure represented by flood extents.

Flood extent

The predicted area of flooding from rivers, the sea or surface water based on the Scottish Environment Protection Agency Flood Maps.

Flood hazard-exposure

The degree to which people or other systems may come into contact with flooding. In this project flood hazard-exposure is estimated spatially as the proportion of residential addresses located within flood extents.

Flood return period

The average interval between floods of a given magnitude. It is a measure of the rarity of flood events - the longer the return period, the rarer the event.

Population-weighted centroid

A summary single reference point which represents how the population at census time was spatially distributed and grouped within the census unit.

Property level protection

Flood protection measures implemented for individual properties, which either keep the flood waters outside the property or minimize the damage if flood waters enter the building.

Proxy indicator

An indicator that provides an approximation of the factor influencing social vulnerability to flooding, e.g. the density of social networks is represented by a proxy indicator of older people living on their own as they are likely to be the most socially isolated.


One of the dimensions of vulnerability, which reflects the personal characteristics, namely age and health status, that increase the likelihood that a flood event will have negative health and well-being impacts on people.

Social vulnerability to flooding

The varying degree to which people's health and well-being would be negatively affected by flooding (the higher the vulnerability, the greater the negative effect of flooding).

Standard deviation

A measure expressing how much the scores in a group differ from the mean score for the group. Standard deviation is found by taking the square root of the variance - which is the spread of the scores within the group.


A statistical process of re-calculating values for variables or indicators measured using different scales in order to present them on a uniform scale.

Surface water flooding

Flooding that results from rainfall runoff flowing or ponding over the ground before it enters a natural ( e.g. watercourse) or artificial ( e.g. sewer) drainage system or when it cannot enter a drainage system ( e.g. because the system is already full to capacity or the drainage inlets have a limited capacity) ( JBA, 2014).

Undefended flood extent

The areas that may be affected by flooding if no flood defences were present, in other words assuming that all areas are undefended. In practice some areas identified as flood prone do have defences in place and thus have a lower chance of flooding than the data would suggest.


A statistical measurement of a score's relationship to the mean (average value) in a group of scores. A Z-score of 0 means the score is the same as the mean (average value). A Z-score can be positive or negative, indicating whether it is above or below the mean and by how many standard deviations. Z-score standardisation represents the deviation of a raw score from its mean in standard deviation units.