DAM REMOVAL
There are many reasons why the removal of dams has moved into the public view. The risk that aging dams pose to communities, the cost of maintaining a dam, the usefulness on an old dam, the problems of repairing aging dams, and the environmental degradation of rivers as well as species and habitat.
POSSIBLE POSOTIVES
There are many positive aspect to removing aging dams. Safety is a key factor. The weakened aging materials that old dams are made of pose a hazard to down stream communities. Removing old dams brings the possibility of restoring the natural flow and habitat of the river system. Removing old dams stops the degradation and incision of the river channel. Removing a dam brings the possibility of restoring species migration patterns and rebuilding wildlife habitat. There is also an aesthetic value that comes from removing man made structures from nature.
Figure 7: Before and after pictures of a dam removal project in Baraboo, Wisconsin
Source: http://bataviansforahealthyriver.org/removal_photos.htm
POSSIBLE NEGATIVES
There are some possible negatives to removing dams. There are ecological risks to removing dams; these risks vary depending on factors such as dam size, dam, river, and watershed characteristics, dam age, and dam function. Dam removal can affect down stream water quality by releasing contaminant containing sediment. Old dams may be impounding sediment containing pollutants from up stream sources. The release of impounded pollutants could have a detrimental effect on the environment downstream.
RISK ASSMENT
Risk assessment of dam removal needs to be done before any work concerning the removal of a dam. The balance of pros and cons need to be weighed. Looking into places where dams have already been removed and comparing them to areas of possible dam removal is important when envisioning possibilities. Pre removal assment of a dam is imperative because a study could determine what pollutants and in what quantity would be released if a given dam were removed.