These are just a small sample of dam failures that span throughout the history of time, but they show that while they may seem an quite hazard, they are anything but. Dams have been shown to wipe out entire towns and villages and destroy crops, which when happens in a poorer area can wipe out their economic means of survival.

Dam construction is almost a completely human construct, except for beavers who construct them for homes. This isn’t to say that they aren’t linked to any of the other natural hazards out there. Ground shaking due to earthquakes can be damaging to dams like in the instance of the partial failure of the Van Norman Dam in 1971. Any dam in an area that is in danger of ground shaking from earthquakes, like the Sacramento River Delta, is at danger themselves.

The construction of dams can cause channel erosion and human activities increase both the magnitude and frequency of floods in small rural drainage basins. Floods are directly related to rainfall and runoff and dams can be overwhelmed by floods or an
exponential increase in rainfall.

Many mitigation strategies are attempted on dams and unfortunately in the past some may have caused more harm than good.

It is possible for this to be a successful mitigation strategy, but it needs to be done appropriately for it to be effective. This can also lead to a loss in revenue which makes it controversial. Another successful mitigation strategy is to regulate the temperature of the water released from the dam, which is meant to imitate what the natural river temperature should be during each season. However, the issue with this mitigation strategy is that it is unlikely that there is enough water at the right temperature to be released.

The most successful mitigation strategy is dam removal, though it is possibly the most expensive. Studies have been done to forecast the avian response to the Elwha River restoration and the return of salmon runs and are promising. Even shortly after dam removal you could see results “Numerous fish have spawned above the dam now.” This year, Chinook, pink, and coho salmon plus steelhead have spawned in river reaches previously blocked. The river ecosystem is undergoing a dramatic transformation and is a living laboratory for scientists. Though there is a downside with the Glines Canyon Dam removal in particular because there is the possibility that a single bridge may need replaced due to increased erosion after the dam was removed.

Based on the success of the removal of dams on the Elwha River system I would propose dam removal as a mitigation strategy for other dams, at least in the Pacific Northwest where it is shown to work. Another possible mitigation strategy would be a more accurate system to determine the service life of dams, but it is very difficult as shown in this study 

A combination of these mitigation strategies would allow us to determine which dams pose the biggest hazard and then remove them. Dams could be picked for removal based on highest need because of their danger to human populations and river ecosystems.
