When rainwater is present in small amounts (e.g., the volume that can fall on your piece of property during a light rainfall) it is easy to handle and does a lot of good for our ecosystem. When rainwater is present in large amounts (e.g., running off large parking lots in subdivisions) it becomes fast-moving stormwater that is extremely costly to our environment and economy. Technically, the term stormwater refers to excess rainwater in undesirable places which requires a system of engineered pipes and channels that move large volumes of rainwater away from developments and transport it to a discharge system (often a lake or river or the ocean). This collected water has negative impacts on the environment, is very expensive and challenging to deal with, and can often result in flash flooding.

WP Glossary Term Usage