To my knowledge, this depends on the dam in question
For large dams in developed countries it's relatively easy to contain that risk (move people a few kilometers away from thedanger zone) in contrast to a nuclear plant.
Large chemical industries have no problems getting insurance as far as I know -or do you have credible sources stating otherwise?
I've never heard of countries considering the entire danger zone from a large hydroelectric dam uninhabitable. They're so large that it's simply not feasible. Take the largest hydro station in Sweden for example, Harsprånget[1]. The government assessment for what happens when that dam breaks assumes it takes out a very large geographical area, among other things the entire city of Luleå (which is near the coastline).
No large chemical industry handlng dangerous chemicals, in developed countries or otherwise, has an insurance large enough to pay for huge expensive spills. That's why the company usually defaults when it happens and leaves the cleanup for the government later on. This has happened on numerous occations in the US, Europe, and over here in Sweden.
