A Water Sensitive Urban Design (WSUD) report calculates a developments ability to treat rainwater collected from the additional hard surfaces introduced. A site which normally features a large percentage of lawn and vegetation in which is nourished by rainwater will now have a significant amount of hard surface area collecting the rainwater and pushing it through the stormwater drainage system.
Not only is there a large increase in rainwater being collected and sent to the stormwater drains, but there is also sentiments and contaminants being collected and sent to the stormwater drains.