Buddy go check your manuals. One in 10 usually means one in 10 years. Everybody can make a mistake if you are not up on thing. BTW me wan PE too, just electrical. Me just pass the exam and should get the certificate thing in couple weeks.
Again, it can occur with a probability of 10% in any given year.
Buddy what you stated here is in line with what I expected. This is in line with the "0.1 events per year" I provided in my definition above. It is very different from what you initially stated which was "probability of 10% to occur at any time of the year." No hard feelings.
In the US we built our electric substations to 100 years flood plain levels. Hurricane Sandy created havoc in New York so we will be designing to the new FEMA 100 years flood plain maps. This is something people will be hearing a lot about that is driving rate increases.