Buildings and surfaces—whether roads or parking lots—are usually impermeable, and run-off drainage water has to be accommodated. Ideally, development should be planned in order to maximize the permeability of a site, and the rate of surfacewater run-off should be slowed by ensuring that buildings have a small footprint, by employing green roofs, and by minimizing the use of impermeable roads and footpaths. However, there is usually some decrease in the total permeability and drainage capacity of land when a greenfield site is developed. The consequent surfacewater run-off has to be dealt with either on or off site.

In built-up areas the conventional drainage approach has been to provide a surfacewater or combined drainage system; the ...

Get Construction for Landscape Architecture now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.