The sediments will settle to the bottom of the stream or end up in drainage ditches or any lower elevations on the ground.
Saint Petersburg has a population of 5 million.
Moscow has a population of 11 million.
Minsk (the capital of Belarus) has a population of 2 million
Kiev (the capital of Ukraine ) has a population of 3 million
So the biggest city of those is Moscow. - a lot bigger than others
The thick layer is the-crust