Storm Sewer System

The Village's storm sewer system is comprised of 123 plus miles of pipe and 5,320 inlets, catch basins, manhole structures, 24 miles of open drainage ditches, and 6 lift/pump stations. The storm sewer system also contains three regional detention basins owned and maintained by MWRD and one owned and maintained by the Village. Together these basins provide 1,725 acre feet of storage which is equivalent to over 562 million gallons of stormwater. There are also smaller more localized detention basins which are owned and maintained by the Village, homeowner's associations, or individual homeowners. This system conveys water to rivers or streams in or near Northbrook including the Skokie Lagoons, the Middle Fork and West Fork of the North Branch of the Chicago River, and the Des Plaines River.

Storm Sewer System Operation

As rain falls occurs in Northbrook during an event, stormwater runoff flows by gravity over and through drainage swales, drainage ditches, curb and gutters to storm sewers or stormwater detention basins. Stormwater detention basins are designed retain water and releases it to storm sewers slowly so as to help avoid inundating the system. As stormwater is collected into the storm sewer system it then travels into one of 4 water ways: the Skokie Lagoons, the Middle Fork and West Fork of the North Branch of the Chicago River, and the Des Plaines River. Which waterway storm sewers flow into is dependent on what watershed they are located in.

Causes of Flooding in Northbrook

• Flooding can be the result of one or a multitude of factors including but not limited to:
• Rainfall during long duration or short duration - high intensity rainfalls, runoff can enter the storm sewer system in Northbrook too quickly and inundate it.
• Flooded Outlets - The long duration-low intensity or short duration - high intensity rainfalls can cause the levels of the rivers and streams to which the Village's runoff drains to flood and prevent the Village's storm sewer from draining. This can be attributed to the runoff from properties upstream of Northbrook. As the levels of these rivers and streams go down, the storm sewer system will again drain.

Common Myths About the Storm Sewer System

• Myth Number 1: The Village has gates or valves it can open to quickly drain water from roads and yards in the Village.
  • Answer: The Village does not have gates or valves it can open to quickly drain storm water away. Residents may see water drain away quickly when the rivers and streams our storm sewer system drains to have receeded enough to allow our outlets to drain.
• Myth Number 2: If MWRD opens the "locks" in Wilmette, Northbrook will experience no or less flooding.
  • Answer: If MWRD opens the "locks" at Wilmette Harbor, there is little to no benefit to Northbrook because most of Northbrook does not drain to the North Shore Channel. The water ways in which Northbrook's stormwater drains primarily flow through Chicago, however Northbrook is too far upstream for an opening of the locks in Chicago to make a significant or instantaneous difference in the river levels in Northbrook. It's important to note that MWRD is an independent organization and not regulated by the Village of Northbrook