Bellevue Flood Mitagation and Stormwater Management

As part of their Senior Design Capstone course, Civil & Environmental Engineering students created designs for flood impact mitigation measures in Bellevue, Iowa, including culvert improvements, drainage channels, and residentail flood walls.

Recent updates to the flood maps of Bellevue, Iowa, have carried serious impacts for citizens within the community. The updates have added multiple homes along the Dutel Hollow main branch and Dutel Hollow second branch drainage ways to the 100-yr floodplain that were not there previously. The addition of these homes into the floodplain will trigger lenders to require homeowners purchase flood insurance to mitigate the risk of living in the newly expanded floodplain.

The Engineering project team was tasked with helping the City of Bellevue  explore available options that may take these homes out of the floodplain and prevent future development from adversely impacting the floodplain. After a site visit, the team realized that the drainage system was unusually complex and modeling the entire drainage corridor would not be possible due to time limitations and lack of detailed survey information.

Through meetings with the client and stakeholders in the community, the team learned that the culvert beneath Highway 62 may not be sized to meet the current stormwater flows of the community. Considering this new information, the team decided to investigate the effects of resizing the culvert beneath Highway 62 to see if changes to the culvert could lower the water surface profile enough to remove homes from the floodplain. The team also decided to also examine choices homeowners can consider to manage their risks that is independent of a large-scale project.  The options the team chose to evaluate were boiled down to two options; rely on flood insurance to manage the floodplain risk or build a flood wall around the walkout basement of their home to remove them from the 100-yr floodplain.

The final deliverable includes designs for resizing an existing culvert to better manage stormwater and designs for residential flood walls that can help homeowners make decisions about mitigating their own risk and flood insurance costs.  In addition to the designs, the team provided costs estimates.