Other Dam Removal Considerations

In recent years, 138 dams have been removed throughout New England to help restore natural flow and temperature regimes to over 18,000 sq. km of the river (Hare and Moore, Unpublished). While removing dams may seem like an easy solution to combat rising stream temperatures, removing a dam will have both positive and negative consequences that need to be considered.

Ecosystem benefits of dam removal

Increased river connectivity
Decreased river temperatures
Shorter water residence times

Ecosystem consequences of dam removal

Mass release of built-up sediment
Decrease in ecosystem nutrient processing due to shorter residence times
Costly to remove a dam
- On average, the cost to remove a dam was $30,620 per additional vertical foot and $1,360 per additional horizontal foot based on past removals (Blachly and Uchinda 2017).

What needs to be considered when planning dam removal?

Do the ecosystem benefits outweigh the consequences?
Historical upstream land use and industrial practices for understanding legacy sediment build-up behind dams
Local fish and aquatic species downstream of dam removal

Figure 1a (left): Dots represent locations of dams in New England (Hare and Moore, Unpublished).

Figure 1b (right): Watershed boundaries upstream of removed dams in New England. Dam removal data for Maine was not available (Hare and Moore, Unpublished).

Citations

Blachly, B., & Uchida, E. (2017). Estimating the Marginal Cost of Dam Removal. Retrieved April 16, 2021, from https://digitalcommons.uri.edu/cgi/viewcontent.cgi?article=1001&context=enre_working_papers#:~:text=A%20limited%20number%20of%20studies,to%20%2424%2C390%20per%20vertical%20foot.

Hare, Danielle and Moore, Eric, Jackson, Kevin, Haynes Adam, & Helton, Ashley. (n.d.). Hot Dam: Stream temperatures downstream of dams across the United States. Unpublished.