What Gidde said :-).

Plus, the after-it-crosses-the-coastline effect builds a delta [I]outward[/I. Your delta as drawn is all about before a river reaches a coast, slowing down and meandering til it fragments a million ways. That's a real effect, but possibly lesser than the building-outwards one. So unless a delta starts in a bay of some sort (it does happen) it'll mostly stick out instead of being "onshore".

There's other considerations: it takes a fairly big river to pick UP enough dirt, before it'll DROP enough to make much of a delta. And if the ocean where it empties has strong currents right on the shore, there went the "water slows therefore drops suspended dirt" condition - and the silt just gets carried way out to sea.