Thanks jbg, I surely will!

What he's talking about, Mel, is the fact that rivers with deltas have a ton of dirt in the water, that they've picked up from the lands they've gone through. When one of these hits the ocean, the flow slows and the dirt falls out of suspension (kinda like if you stop stirring a bucket of sandy water at a beach). Over time, all that dirt builds little islands right there at the river mouth and a delta is born. It grows because now the river water doesn't slow down until after it passes the islands, so the next islands are out further. Take a look at the mouths of the Amazon for one heckuva big one.