The natural response of a catchment, characterised by infiltration, evaporation, attenuation, surface storage and reduced runoff, is alte ed by the urbanisation process. The construction of buildings, roads, and pavements increases the impermeability of the catchment and thus the volume of water leaked into the subsoil is significantly reduced. Furthermore, the changes in land use involve loss of vegetation, which consequently blocks the evapotranspiration mechanism of stormwater reduction. The classic "end-of-pipe" approach to these problems, which is characterised by improvement in the capacities of streams and drainage ditches, actually increases the velocity of flow. This reduction of the catchment response time consequently increases the maximum rate of flow discharging to the drainage system and finally increases the frequency of significant floods. An alternative to this approach is source control promoting stormwater reuse and application (waste minimisation, reuse, recycle). Researchers dealing with stormwater drainage and flood risk management have been increasingly interested in source control, being in accordance with the basic concepts of sustainable drainage as described by Butler and Parkinson [5], aiming at minimising the amount of runoff by infiltration for aquifer recharge, utilising the natural (or already existing) pathways of the catchment for stormwater drainage and reducing risk of flooding using non structural means where possible as the latter have proved to be at best partial solutions. This can be achieved by a reduction in rainfall runoff volume (infiltration techniques) as well as by an increase of time to peak (grass swales, which slow down runoff).
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