We can reason about the 'relativeness' of disasters. There are the folks who are alive and homeless because their homes were destroyed by the water, and there are people who are alive and homeless because of the evacuation zone around the reactor.
Given the readings for radioactive nuclides outside the Fukushima plants [1], once they are fully engaged in the process of the cleanup, the plan is to allow everyone to return to their homes. Living and working in Fukushima Prefecture will be no more and no less hazardous than it was before the tsunami, and the houses and farms and infrastructure is generally intact and ready to move in.
For folks who lost their home in the tsunami, once the roads and infrastructure have been repaired, they can begin re-building their lives.
So when we think about the relative scale of the disaster to people we might assign a value 'x' to someone who is evacutated for a period of time, and then returns to their home and neighborhood as it was pre-evactuation. And a value 'y' to someone who evacuated and at some point will return to the land where they used to live and can start rebuilding their lives and community.
I can't speak for the people, I don't live there, but if I were told I was going to be a member of either group x or group y I would prefer to be in group 'x' as it would seem to me to be the 'lesser' of two disasters.
So at some level, everything is a disaster, but in this discussion I continue to feel that the tsunami/quake combo was the 'real' disaster and the ongoing work to stabilize the reactors which were damaged by that disaster as one of many responses to the disaster akin to people working to prevent cholera and other outbreaks and to restore basic services like drinking water and electricity. Those people who are involved in surveying damaged buildings, recovering downed power lines, clearing debris from water treatment plants are in some ways more at risk of a life threatening injury than the engineers working to get the Daichi plant stabilized and into clean-up mode.
[1] "Gamma Dose Rates in 47 Prefectures
Gamma dose rates are measured daily in all 47 prefectures. On 10 May the value of gamma dose rate reported for Fukushima prefecture was 1.7 µSv/h. In all other prefectures, reported gamma dose rates were below 0.1 µSv/h with a general decreasing trend."
"Gamma Dose Rates in Areas More Than 30 km from Fukushima Daiichi Plant
Gamma dose rates reported specifically for the monitoring points in the eastern part of Fukushima prefecture, for distances of more than 30 km from the Fukushima Daiichi plant, showed a general decreasing trend, ranging from 0.1 µSv/h to 20.3 µSv/h, as reported for 10 May."
Let's say we're unlucky enough to live in that 20.3 µSv/h environment. Our daily dose is 487 µSv. Our monthly dose is 14 mSv. Our yearly dose is 178 mSv, way above pre-Fukushima radiation worker permitted dosage.
The tsunami is obviously independently of that the far worse disaster.