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Flood Mitigation and Water Quality Analysis

City of Rochester Flood Mitigation and Water Quality Analysis
Flood Mitigation and Water Quality Analysis

Location:  Rochester, Minnesota
Client:  City of Rochester


The City of Rochester was in the process of making efforts to develop long-term stormwater management strategies for Cascade Township. HEI was contracted by the City to provide the technical information needed for surface water management decisions for Section 7 of Cascade Township, including addressing the existing risk of communities flooding. 

In 2018, HEI assisted the City in developing a comprehensive hydrologic and hydraulic model that was used to assess the performance of five regional stormwater ponds situated along the Douglas State Trail. The 2018 study revealed that the ponds do not provide sufficient storage volume to prevent a risk of flooding to structures upstream (west) of 50th Avenue NW.

The Project

Following the 2018 study, further analysis was warranted, including evaluating downstream flooding. Three primary technical objectives were established for this study to satisfy its goals: 
  1. Evaluate the performance of the existing infrastructure and the impact of flooding on homes in the area using InfoSWMM modeling software.
  2. Identify cost-effective regional flood storage and other flood mitigation features in the watershed to provide further flood resiliency to the communities.
  3. Evaluate the water quality of the stormwater runoff throughout the study area, the effectiveness of the existing stormwater management features to remove total suspended solids and total phosphorus, as well as evaluate the removal efficiency of the recommended flood mitigation feature identified in the task above. 
HEI completed the analysis in 2019. The model was validated by a third party and subsequently used more effectively to design a downstream road crossing. 

Client Benefits

  • The hydraulic model was used to better inform the design of future drainage infrastructure and development.
  • Evaluation of flood risk to existing communities.
  • Identification of the most cost-effective stormwater features in the watershed to help mitigate flood risk. 
  • A quantification of the water quality of the runoff and pollutant removal currently occurring in the watershed.