Steamboat Rock Dam Flooding

Prepared by Paul Speed, P.E.

​LT Leon Associates prepared a hydraulic model of the Iowa River using the United States Army Corps of Engineers hydraulic modeling program, HEC-RAS.  The model includes the Steamboat Rock dam, downstream bridges, and land and bathymetric (underwater) survey data near the dam.  The model was analyzed for multiple rainfall scenarios including high probability rainfall events (2-Year and 5-Year rainfall events) and low probability rainfall events (100-Year rainfall event).  The existing conditions scenario was evaluated along with multiple scenarios that lowered the height of the existing dam incrementally including a full removal scenario.  Refer to the graphic below for approximate flood elevations within the Pine Ridge Park campground.

​Key observations from the hydraulic analysis include:

• 100-Year Rainfall Event
  • At the Pine Ridge Park Campground in the full removal scenario the 100-Year water surface (WS) was 0.37’ lower than the existing conditions scenario.
• For the 5-Year rainfall event
  • At the low point in the gravel road (in front of the Iowa River Conservation and Improvement club)
    • Existing WS = 2-feet deep over the road
    • Full Removal Scenario WS = below the road
• For the 2-Year rainfall event
  • At the Pine Ridge Park Campground
    • Existing WS = 2-feet deep over the river bank
    • Full Removal Scenario WS = within the banks of the river
  • At the low point in the gravel road (in front of the Iowa River Conservation and Improvement club)
    • Existing WS = 1.5-feet deep over the bank

Full Removal Scenario WS = within the banks of the river