Phase 4 Drainage - Drainage Masterplan

Milestone timeline:

City engages Davis & Floyd to complete a comprehensive drainage masterplan
Completed: Aug 24, 2021
Aug 24 2021
Davis & Floyd present status update to Public Works Committee
Completed: May 4, 2022
May 4 2022

City of Isle of Palms hired Davis & Floyd to develop a capital improvement plan for storm water management into the future. 

Project Updates

Drainage Masterplan Update - May 2022
Tuesday, May 17, 2022

Work Complete to Date:

  • Full inventory and assessment of existing drainage infrastructure for phase 4 study area.
  • Water level monitoring stations installed near Ocean Boulevard, county park, and marina.
  • Rainfall monitoring station installed at county park.
  • Provided short-term maintenance recommendations based on field assessments for phase 4 study area.
  • Completed existing conditions hydrologic and hydraulic assessments of phase 4 infrastructure for both extreme and typical storm events. This includes high intensity rain bombs as well as elevated tides from sea level rise.
  • Developed preliminary solutions for high-priority areas within the phase 4 study area as identified through the existing conditions assessment and confirmed by city staff. High-priority areas are classified as those that experience more than 6 inches of flooding for more than 30 minutes.
  • Identified preliminary solutions for low-priority areas within phase 4 study area.
  • Reviewed island-wide ditch/channel maintenance program.

Next Steps:

  • Develop cost estimates for preliminary solutions for high-priority areas.
  • Continue evaluating alternatives for high-priority areas to fiend the most efficient and economical long-term solution.
  • Continue evaluating options to solve flooding in low-priority areas.
  • Identify funding options for all alternatives.
  • Set up meeting and work with residential property owners to evaluate development standards in terms of stormwater management.
  • Identify and consult with specialty contracts (e.g., stream restoration contractors) to develop long-term solution for island-wide canal/ditch/channel systems.
Drainage Masterplan Update - April 2022
Tuesday, April 19, 2022
  • Inventory and conditions report is complete and presented in easily understood Google Earth format (see attached screenshot example)
  • Modeling to identify problems is complete
  • Staff met with Davis & Floyd on April 24th to verify issues identified and modeling match conditions found in the field
  • Davis & Floyd is working to develop conceptual solutions to issues identified
  • Davis & Floyd is scheduled to discuss their progress and possible solutions with Public Works Committee at their May 4th meeting
  • Davis & Floyd will soon begin reviewing City’s development standards to address shortcomings.
Drainage Masterplan Update - March 2022
Tuesday, March 15, 2022
  • Project is progressing well and on schedule
  • 625 watersheds delineated
  • Inventory of current conditions is complete
  • 2D and 3D modeling is underway
  • Monitoring has not measured any significant rain events yet
  • Potential projects are being identify now
  • On track for project completion by the end of the year
Drainage Masterplan Update - February 2022
Tuesday, February 15, 2022
  • Project is progressing well and on schedule.
  • 625 watersheds delineated
  • Inventory of current conditions should be completed this week
  • 2D and 3D modeling begins week of February 14
  • Monitoring has not measured any significant rain events yet
  • Davis & Floyd, City staff visited Eadie’s work this week to visualize problems
  • Assessment and evaluation of collected data is underway
  • On track for project completion by the end of the year
Drainage Masterplan Updates - January 2022
Tuesday, January 18, 2022
  • Project is progressing well and on schedule.
  • Field work is complete
  • Rainfall and water level monitors are installed and operational
  • Assessment and evaluation of collected data is underway
  • On track for project completion by the end of the year