Function

The storm water drainage system is defined as the system of roadside drainage, roadside curbs and gutters, curb inlets, swales, catch basins, manholes, ditches, pipes, lakes, ponds, sinkholes, channels, creeks, streams, storm drains, and similar conveyances and facilities, both natural and man-made, located within the Memphis and Shelby County through which storm water is collected, stored, or conveyed, whether owned or operated by the municipality or another entity.

The function of the storm water drainage system is to direct runoff from precipitation events such as rain or snow melt away from our property. We have altered the landscape as we have developed and grown as a City. Our business and home roofs, sidewalks, streets, and parking lots are not the vegetated areas they once were. When vegetated, land largely absorbs storm water. But when developed, the amount of impervious area (hard surface area that does not absorb storm water) increases. Without the storm water drainage system, there would be nothing in place to direct storm water runoff away from our homes and businesses. The storm water drainage system is designed according to the layout of the land (i.e. low points and high points) and the impervious area surrounding it.

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A commonly known part of the storm water drainage system is the street inlet.

Vegetated or concrete lined swale.

A lesser known part of the storm water drainage system is the vegetated or concrete lined swale.

You commonly see these along streets to direct the flow of storm water.  You will also see grate drains on large impervious areas like parking lots or in low-lying vegetated areas.

 

Another part of the storm water drainage system is the concrete ditch, or channel.

Basin.jpg

Storm water may empty into a type of basin like this (which looks like a lake or pond).

the City of Memphis
Storm Water
Drainage System

Memphis has two separate underground systems: the storm water drainage system and the sanitary sewer system. The sanitary sewer system carries used “wastewater” from homes and businesses to a waste water treatment facility where it is cleaned and then discharged into the Mississippi River. The storm water drainage system carries ONLY rain water and it is discharged WITHOUT treatment into a nearby waterbody.


The water from the inlets on the streets will flow within the underground drainage system and may empty into one of these visible channels. It can connect to or be a part of a natural waterbody.  All the storm water drainage will either be discharged directly into a surrounding waterbody or into a basin where the storm water will be retained or detained until evaporated or slowly discharged into a waterbody either directly or gradually through the MS4.

 
Gurgle Factoid!

Did you know that ‘ditches’ are often channelized creeks or streams? You can find fish and wildlife in these channels. What you throw in them has a very direct effect.