Factoria Area Storm Drainage Modeling

Flooding in the Factoria area of the City of Bellevue has impacted public roads and several businesses over the past several years. The City retained WSE to develop hydrologic and hydraulic models to characterize existing conditions and evaluate potential solution alternatives.

Role/Services: WSE’s role on the project included developing an HSPF hydrologic model of the basin which was used to generate inflows to the storm drainage system.   EPA-SWMM and HEC-RAS hydraulic models were developed and calibrated to several recent flood events  and then used to characterize flooding for 2- through 100-year return period floods. The models were then used to evaluate stormwater system improvements to reduce flooding.  The effects of potential storm system improvements on downstream flows were evaluated to ensure the improvements would not impact downstream conditions.

Outcome: The City will be implementing the suggested storm water solutions and has retained consultants, including WSE, to finalize the design of conveyance improvements.