Figure 2: The fish ladder remains intact, even though the dam was removed

Figure 1: Showing the landscape before and after the Jordan's Point dam removal

In conclusion, the HEC-RAS model indicates reduced ponding and a return to more natural, near-critical flow conditions upstream of the former dam location, which benefits fish movement and habitat. The restored river hydraulics allow fish to swim more easily and promote healthier ecological conditions. The results also show reduced flooding near the dam site, suggesting that dam removal not only supports ecological restoration but also improves flood resilience for the town of Lexington. With more complete data, further analysis of downstream conditions would be warranted to confirm the absence of negative impacts; however, no adverse effects were evident in this study. Overall, this project demonstrates how HEC-RAS modeling can be used to evaluate dam removal as a tool to improve community safety and restore fish habitat across the United States.

Fish ladders have shown mixed success in restoring fish passage, and many do not fully replicate natural upstream migration. Dam removal was therefore especially beneficial, as it allowed fish to move upstream freely without relying on a ladder. Even when fish ladders are passable, they can delay migration, increase energy expenditure, and reduce survival compared to unobstructed river flow. These limitations have contributed to population declines in some species, particularly migratory fish that must pass through multiple dams to reach their spawning habitats.

CONCLUSION

Indicators supporting dam removal include lower upstream water-surface elevations during modeled flood events, elimination of backwater and ponding effects, and minimal changes to downstream flooding. The hydraulic results show improved flow continuity and a return to more stable, river-like conditions upstream, reducing flood risk while maintaining downstream stability. From an ecological perspective, dam removal also restores natural sediment transport and uninterrupted fish passage. In addition, the very low Froude numbers observed upstream of the dam indicate slow, ponded flow conditions, which are typically associated with reduced turbulence and lower dissolved oxygen levels. Although fish live underwater, they rely on dissolved oxygen for survival, and these low-energy conditions can stress aquatic organisms. After dam removal, increased velocities and higher Froude numbers promote better mixing and oxygenation, further supporting healthier aquatic habitat.

Disclaimer: This website presents an educational analysis of stream and river hydraulics using HEC-RAS. The modeling is based on simplified assumptions, estimated inputs, and limited available data. All results are for academic purposes only and are not intended for design, regulatory, or implementation use.

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