How To Fix A Flood Control System In South Lakewood

Transcription

1 Cedar and South Street Area Flood Remediation Project Upstream Watersheds 1

2 Cross Section Locations HEC-RAS Model Cross Sections 25-year Flood Limits 10-year and 25-year event between 1 or 2 year event 5-year and 10-year event Overbank water flows west along Cedar at a 10 year event Existing Conditions 2

3 Existing Conditions Existing conditions NA Flow is contained within the channel upstream of the Arch St 60' RCP culvert. Downstream of the Arch Street culvert flow exits the channel primarily on the eastern side. Backwater upstream of Cedar Street forces water to the west down Cedar Street. The channel between the Arch Street culvert and Bradley is insufficient to convey the flows between the 1-year and 25-year storm events as described below. at a 10 year event a 5-year and 10-year event at a 1 or 2 year event a 10-year and 25-year event at a 10-year and 25-year event Overtops roadway at a 25 year event 25-year and 50-year event between 2 and 10 year event 10-year and 25-year event Between 25 and 50 year event Alternative A 3

4 A Basins: This alternative considers 18 acre-feet of off-line storage in basins bounded by Chargin Rd, South St, and the existing channel. Flow would be diverted from the channel downstream of the Pine St or Arch St culvert outlets and discharged back into the channel downstream of Cedar St. Some flow would be maintained in the channel between the points of diversion and discharge to minimize channel permitting issues. The basins would be constructed with a setback from the existing channel bank. This alternative would require culvert crossings of Pine St and Cedar St. Channel Modifications: none other than removing sediment from the Cedar Street culvert. Three houses on South St. and the roller rink property. Channel capacity - between 25-year and 50-year events a 10-year and 25-year event between 2-year to 10-year events a 25-year and 50-year event between 25-year and 50-year event a 25-year and 50-year event 25-year and 50-year event between 10 and 50-year event 50 and 100-year event without modification Channel capacity year event Alternative B 4

5 B Basins: The basins as described in Alternative A are also included in this alternative. Channel Modifications: This alternative considers channel modifications from the outlet of the Arch St. culvert to South Street. A minimum channel top width of 10' with vertical channel banks wa s created for the man-made bank sections of the channel because of space limtiations. More natural sections were widened where space was available to increase channel conveyance capacity. Sediment should be cleaned from the Cedar Street culvert. Improvements to the Cedar Street culvert should also be considered. Three houses on South St. and the roller rink property. Channel capacity year 50-year and 100-year without culvert modifications between 10-year to 50-year events a 25-year and 50-year event between 25-year and 50-year event a 25-year and 50-year event 25-year and 50-year event between 10 and 50-year event 50 and 100-year event without modification Channel capacity 100- year event Alternative C 5

6 C Basins: This alternative increases the storage capaisty of the existing basin to the east of Chagrin Rd by 25%. The basins as described in Alternative A are also included in this alternative. Channel Modifications: This alternative considers channel modifications from the outlet of the Arch St. culvert to South Street as described in Alternative B. Three houses on South St. and the roller rink property. Channel capacity year 50-year and 100-year without culvert modifications between 10-year to 50-year events a 25-year and 50-year event between 25-year and 50-year event 25-year and 50-year event Upstream Detention maintains water surface elevations at or below existing levels Culvert capacity 100-year event Channel capacity exceeded between 25 and 50-year event Culvert capacity 100-year event Channel capacity 100- year event Alternative D 6

7 D Basins: 4.3 and 0.07 ac-ft at bypass culvert inlet Culvert - 4'x6' box culvert, connect culverts from exisiting basin and eastern watersheds No private property acquisition Channel capacity year Culvert capacity year event between 25-year to 50-year events Culvert capacity year event between 25-year and 100-year event 25-year and 50-year event Questions? 7