Overview:
Flooding events experienced by the City of Logan brought into question the accuracy of the regulatory floodplains shown on effective Flood Insurance Rate Maps (FIRMs). Therefore, J-U-B Engineers initially completed the following tasks:
- Determine the accuracy of regulatory floodplains and existing levee systems
- Update flood hazard information
- Develop a coordinated plan of flood mitigation and channel restoration/stabilization improvements
Before the revised flood hazard information could be submitted to FEMA, widespread flooding occurred in Cache County following record snowmelt in the spring/early summer of 2011. Flood hazard modeling/mapping developed by J-U-B was successfully utilized to implement flood fighting strategies during flood events along both Blacksmith Fork River and Logan River in May and June of 2011. Following the 2011 flood, J-U-B staff assessed flood damages, prepared construction plans for channel restoration/stabilization improvements under the NRCS Emergency Watershed Protection (EWP) program; and completed a PMR submittal to reflect all stream restoration projects.
Project Components:
Hydrologic and Hydraulic services for the project included:
- Hydrologic analysis to revise the regulatory discharges for the Logan River
- Hydraulic modeling of approximately 20 miles of the Logan River, the Blacksmith Fork River, Spring Creek, and Little Ballard Creek
- Geomorphic and sediment transport analyses
- Preparation of digital floodplain work maps
- Evaluation of existing levees to determine whether the levee embankments could be certified
- Preparation and submittal of a Physical Map Revision (PMR)
The design process included the following components:
- Formulation and preparation of channel restoration/stabilization and flood mitigation plans for the Logan River, Blacksmith Fork River and Spring Creek
- Hydraulic design of all channel restoration/stabilization and flood mitigation plan components, including riprap toe protection, rock grade controls, riparian restoration to improve riverine ecology and aquatic/fishery habitat
- Hydraulic design of the 1700 S Bridge replacement over the Blacksmith Fork River, and the Blacksmith Fork berm to provide flood protection for the Country Manor Subdivision
- Preparation of preliminary designs, construction cost estimates, and an implementation/prioritization plan
- Preparation of construction plans and specifications for selected plan components
Design Team:
J-U-B Staff collaborated with Terracon to provide geotechnical services related to the potential levee recertification.
