Overlay Maps

From SEA.unu.edu/wiki

A simple way of identifying areas that would be appropriate - and inappropriate - for development is to superimpose maps of areas of constraint, for instance areas of importance for landscape, wildlife, groundwater protection.

The example below (CPRE/CC, 1995) shows two maps of "tranquil areas" in England. The maps superimpose (in white):

• 4km radius from the largest power stations
• 3km buffers from the most heavily used roads and from major industrial areas
• 2km buffers from other heavily used roads and from the edge of smaller towns
• 1km buffers from roads with medium disturbance, some main line railways, 400KV and 275KV power lines
• noise lozenges from military and civil airfields
• areas of very extensive opencast mining

Note the impact that development has had on tranquil areas (the darker areas) between the early 1960s (top map) and early 1990s (bottom map)!

Advantages:

• very immediate, understandable results
• can be done by non-experts, and used in public consultation
• applicable at all scales

Disadvantages:

• can only be used with impacts/developments that have a spatial component (that are "mappable"): unlikely to be useful at policy level
• can be time-consuming and expensive, especially if done through GIS

Further information: