Answer:
when discharge is high vertical erosion erodes the river bed and larger sediments are transported by transaction the river channel is at its widest and defence as a flow towards its mouth the position is the main process in this part of the river which creates large floor plans and deltas
Oceanic crust is denser than continental crust. Continental crust is more buoyant. :)
http://faculty.chemeketa.edu/afrank1/topo_maps/scale.htm use this website and i think this should fully explain it
