Grand Avenue Extension

Grand Avenue Extension


To alleviate traffic congestion on South Duff Avenue and provide an alternative north-south route across Ioway Creek, the City of Ames extended Grand Avenue by constructing a new roadway, South Grand Avenue.

The structures designed by WHKS include: 

  • Ioway Creek Bridge – 407′ x 51′ PPCB
  • Overflow Bridge – 267′ x 51′ PPCB
  • Golf Cart Underpass – 16′ x 10′ x 112′ RCB
  • Pedestrian Bridge Relocation – 160′ x 10′ Steel Truss

The hydraulics of the project were complex and a typical 1D flood model could not adequately portray flood elevations. WHKS developed a 2D flow model allowing the hydraulics to be analyzed in much greater detail and with increased accuracy. The project resulted in a no-rise certification and met backwater limits set forth in the Iowa Code.

In addition to bridge and hydraulic design, WHKS designed a stormwater wetland, completed hydraulic analysis, and designed the realignment of the Worle Creek Channel. 

The Grand Avenue Extension project received an award from the APWA Iowa Chapter for Project of the Year in the Transportation, Greater than $2.5 M Category.


  • Survey
  • Hydrology and hydraulic design
  • Stormwater wetland design
  • Bridge design
  • Pedestrian bridge relocation


Significant channel grading near the Ioway Creek Bridge was implemented to develop hydraulic efficiency and reduce channel velocities. The grading creates a multi-stage channel that will prevent deposition around the bridge during periods of low to moderate flow. The overflow bridge to the south serves as an auxiliary bridge to convey flood flows during large flood events.