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Watershed Findings

Strand's Initial Watershed Findings

In our study of the west and southwest watershed area of Winnetka, it was critical for our team to investigate and understand the course of events that have lead up to the current stormwater and flood control issues the Village is experiencing.  Our investigations revealed the following important points:

  • The watershed was historically a lowland marsh environment.
  • The area was historically the flood plain for the Skokie River.
  • Strand_Jan_Workshop_Exhibit_1In 1938, a levee system was constructed along the east edge of the Skokie River resulting in the following drainage features:
    • The levee system protects Winnetka from flooding due to the Skokie River.
    • The levee system blocks natural stormwater runoff to the Skokie River.
    • The levee system creates a “bathtub” effect in west and southwest Winnetka.
    • The Village is dependent on pumping to drain the watershed.
  • None of the west and southwest watershed runs off to the Skokie Lagoons.
  • Other features within the watershed like Hibbard Road and Willow Road create bathtubs within bathtubs requiring a series of pumping stations into pumping stations.
  • The vast majority of the watershed is ultimately pumped into the Skokie River at a pump station on Winnetka Avenue.
  • A newer and more powerful computer modeling system has been created to better understand the complicated drainage system serving the west and southwest watershed.
  • This modeling system provides a real-time perspective of what happens in the watershed during various rainfall events.
  • The real-time effects of the July 2011 storm event can be seen here.
  • This model will be used to evaluation various stormwater management and flood control strategies.
  • A wide range of strategies will be considered:
  • Strand_Jan_Workshop_Exhibit_2Each strategy provides a different level of protection.
    • Most green infrastructure is effective on a homeowner-level and provides protection for less intense, more frequent rainfall events.
    • More expansive green infrastructure, local stormwater storage, and conventional conveyance are effective on a neighborhood-level and provide protection for more intense rainfall events.
    • Large scale watershed-level stormwater conveyance, storage, and pumping infrastructure is required to handle significant rainfall events and historic levels of flooding.
    • Each alternative also has a different level of investment to implement.
  • Moving forward our goal will be to find the right balance of stormwater and flood protection, investment, and benefit.
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