  In spite of precautions to avoid the harmful effects of extreme events, we
experience recurrently phenomena that overcome the preventive barriers. These
barriers usually increase drastically right after the occurrence of such
extreme events, but steadily decay in their absence. In this paper we consider
a simple model that mimics the evolution of the protection barriers to study
the efficiency of the system's reaction to extreme events and how it changes
our perception of the sequence of extreme events itself. We obtain that the
usual method of fighting extreme events introduces a periodicity in their
occurrence and is generally less efficient than the use of a constant barrier.
On the other hand, it shows a good adaptation to the presence of slow
non-stationarities.
