1. The challenges

1.1 General presentation of the problem

Stormwater includes all forms of precipitation, whether rain, snow or hail. This precipitation can be collected or intercepted by surfaces of various kinds. These may be artificial surfaces, such as building roofs or paved roads, or natural surfaces, such as tree branches and foliage, or the ground.

• When we talk about stormwater, we include two main categories:

  • Roof water: this is water that falls on roofs and is often channelled through gutters or drainage systems;

  • run-off water (figure 1 ):...