Student team presents Weaver River mitigation options after modeling shows rapid gravel-pit flooding

A Utah State senior design team presented a pre-disaster mitigation study for the Weaver River on March 24, telling the South Weber City Council their model shows a gravel pit near the river could fill rapidly and route floodwaters into areas that threaten U.S. 89 and local property.

"It'll take about 36 hours to completely fill," presenter Joe Fowler said, describing the modeled scenario in which groundwater and high river flows push sediment and water into the pit and then out toward low points. The students said their modeling is preliminary and that further geotechnical data are needed to reduce uncertainty.

The student team reviewed four broad alternatives, including diversion channels, a geotextile or concrete waterproof layer, an urban diversion channel and an underground cutoff wall. Ty Gilbert said the team's preferred option for high flows was a diversion channel: "it would take about 0.333 of the river's flow during flood events," he said, describing a north-side diversion that would reduce pressure on the bank. The students also noted a cutoff wall or CCAM pile wall would likely provide the most permanent groundwater cutoff but carries high construction and permitting costs.

Council members thanked the students and asked technical follow-ups about likely erosion patterns, culvert survivability and project ownership. Council members noted much of the at-risk infrastructure (the gravel pit and affected reaches of the river) lie off city-owned property, and staff said the study could inform more detailed geotechnical work and inclusion of a project in multi-hazard mitigation planning to qualify for federal funds.