Pros+and+cons+of+Dam+Removal

media type="youtube" key="Jg64mfkDbuM" height="344" width="425" Removing any dam comes with uncertain consequences that may result in both positive and negative effects on the surrounding environment. Because it incorporates a wide array of stakeholder wants and opinions, the removal of a dam should be a well thought out process. The decision to remove a dam, therefore, must be supported by evidence from scientific communities, results from other removal projects in similar aquatic systems, and by the vast majority of stakeholders. In support of removal:

One of the reasons to support dam removal is rehabilitation of a healthy aquatic ecosystem that will provide desired ecosystem services. One study by Bednarek et al investigating the consequences of removing the Woolen Mills Dam in Wisconsin found that a newly unaltered flow regime allowed many species of native fish to return to that habitat, while non-native fish populations declined in abundance. Transporting formerly impounded sediment downstream allowed the formation of important fish spawning habitat including pool and riffle areas and gravel and cobblestone streambed reaches, ultimately increasing the biotic diversity within the river. Dammed rivers result in a more lake-like environment in which there is warmer water, and free-flowing rivers are usually colder environments. Because a free-flowing river contains more cold-water species like salmon, trout, and sturgeon, dam removal promotes economically desirable fisheries. Dam removal may benefit the terrestrial environment as well. Another study by Orr et al investigating the effects of dam removal in multiple Wisconsin sites found that plant species diversity and abundance were both positively correlated with time since removal of a dam. Increased riparian zones allows for more bird and mammal habitat, such as bear, elk, moose, wolf, and beaver. This can result in increased hunting and trapping opportunities, providing even more money for state wildlife agencies.

In opposition of removal:

One argument against the removal of a dam is the cost and uncertainty regarding the process and outcomes. Unfortunately, very few long-term studies exist regarding dam removal that managers can base decisions off. Dam removal can be very expensive. For example, the Boardman river dams removal project is estimated to cost around eight million dollars. With that large of an investment, one would want to be sure that the outcomes would be desirable. Some studies have shown that removing a dam may cause supersaturation within the river. Supersaturtion occurs when large amounts of sediment are suddenly released following removal, resulting in increased turbidity and reduced oxygen levels. Massive sediment releases can destroy important spawning and hiding habitats, as well as food resources. Depending on the material used to construct the dam and artificial material built up behind the dam, removal may cause large amounts of lethal toxins to be released downstream. Further, removing dams that provide electric power results in the loss of energy generation. This loss may be filled by creating more power from non-clean energy sources like coal.

References:


 * 1) “The Ecology of Dam Removal: A summary of benefits and impacts.” //American Rivers.// Accessed: 26 November 2009. [|http://www.americanrivers.org]


 * 1) Bednarek, Angela T. 2001. “Undamming rivers: A review of the ecological impacts of dam removal.” //Environmental Management.// 27(6): 803-814.


 * 1) The Boardman River Dams Project. Accessed: 26 November 2009. theboardman.org


 * 1) Orr, C.H., and E.H. Stanley. 2005. “Vegetation development and restoration potential of drained reservoirs following dam removal in Wisconsin.” //River Research and Applications.// 22(3): 281-295.