Not sure where this comparison is going? One dam disaster (Banqiao Dam) caused more death and destruction that almost all other disasters combined. In fact failure of nuclear plants has had remarkably few verifiable deaths.
And compared to the energy one nuclear plant produces, dams seem to have vastly worse death-per-benefit statistics.
Damming a river can cause ecosystem collapse downstream. That's degradation, as I understand the word. And its definitely long-term.
Nuclear proponents always point to the Banqiao Dam disaster, and it's always a misleading argument because that dam was built to control downstream flooding as well as provide power and its failure was probably attributable to how the flood control aspect was mismanaged - by holding back too much water for too long out of fear of downstream flooding, they ended up overfilling the reservoir. If China hadn't bothered with hydroelectric power, the dam would still have to have been built and all those people would still have died when it failed, you just wouldn't be able to use their deaths to make nuclear power look better. (Also, nuclear power didn't exist back when that dam was put into operation, and given the quality of engineering that went into it that's probably a good thing.)
I hoped merely pointing out that discrepancy would suffice - how ben_ws comment compared the history of nuclear accidents to the potential dangers of dams.
Potential scenarios are very important in determining probabilistic risk. Simply showing "it hasn't happened yet" is not a valid way to assess risk. This is the reason it costs more to build and keep nuclear plants safe, than it does dams.
And compared to the energy one nuclear plant produces, dams seem to have vastly worse death-per-benefit statistics.
Damming a river can cause ecosystem collapse downstream. That's degradation, as I understand the word. And its definitely long-term.