The water cycle (also known as the hydrological cycle) describes the various states of water as it moves through the environment - falling as rainwater, infiltrating to groundwater, moving toward streams, evaporating to cloud systems, and so on.
As it moves through the environment, water interacts with natural
systems. Trees intercept rainfall, soil and humus layers attenuate stormwater runoff
and infiltrate it to ground, and terrestrial and aquatic vegetation captures and transpires water back to the atmosphere.
Land development disturbs these natural
processes through vegetation clearance and soil modification. The developed site
, with impervious surfaces and kerb and pipe systems, tends to bypass natural
systems and direct large stormwater volumes to lower catchment areas, resulting in flooding and potentially damaging effects to natural
stream and wetland environments.
A WSD approach to development protects and enhances existing 'natural
' processes in the catchment. Where impervious surfaces do occur, stormwater runoff
is directed to vegetated landscapes and devices such as raingardens and swales, which mimic 'natural
' processes through enhanced infiltration, transpiration and attenuation in floodplains.