Some Basic Stormwater Definitions

Equivalent Residential Unit (ERU):

An average of the horizontal impervious area of single family residential units within the city. The horizontal impervious area includes, but is not limited to, all areas covered by structures, roof extensions, patios, porches, driveways and sidewalks.

Impervious Area:

The area of land, measured in a horizontal plane, that has a surface that has been compacted or covered with a layer of material so that it is highly resistant to letting water soak into the ground. It includes, but is not limited to, semi-impervious surfaces such as compacted clay, as well as streets, roofs, sidewalks, parking lots and other similar surfaces.

Stormwater:

Water that directly results from a rainfall event.

Stormwater System:

Includes all natural and manmade drainage elements used to convey stormwater from the first point of impact with the surface of the earth to a suitable outlet location internal or external to the boundaries of the city. The stormwater system includes but is not limited to pipes, channels, catch basins, curbs, gutters, streams, ditches, wetlands, sinkholes, pub stations, roadways, detention/retention basins, swales, ponds and other stormwater conveyance and treatment facilities whether public or private.

Surface Water:

All surface natural and man-made water bodies, including but not limited to all lakes, rivers, canals, wetlands, sloughs, streams, territorial waters and the ocean into which stormwater runoff directly or indirectly discharges.