The Advancing Red River Delta, Vietnam
The delta of the Red River (along the coast to the center-left), is a flat, triangular region of 15,000 km². It is smaller but more intensely developed and more densely populated than the Mekong River Delta.
Once an inlet of the Gulf of Tonkin, the Red River Delta has been filled in by the enormous alluvial deposits of the rivers over a period of millennia, and it advances one hundred meters into the Gulf annually.
The Mekong delta, on the other hand, covering about 40,000 km², is a low-level plain no more than three meters above sea level at any point and criss-crossed by a maze of canals and rivers.
So much sediment is carried by the Mekong’s various branches and tributaries that the delta advances sixty to eighty meters into the sea every year.