What is a storm surge? 1 A huge, destructive swell of water produced by a tornado.
2 A huge, destructive swell of water produced by a rain storm.
3 A huge, destructive swell of water produced by a hurricane.
4 A huge, destructive swell of water produced by a blizzard.

An informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.