Answer:
Conditions at the base of a glacier increase glacial flow velocity -
Steeper slope
Smooth rock / glacier contact
Colder basal water temperature.
Explanation:
Steeper slope and smooth rock/glacier contact will increase glacial flow velocity because higher the steepness higher the velocity and smoothness will apply less friction.
Due to decrease in ice thickness the load at the bottom of the glacier will decrease, and we know that the glacier flows under the load of itself, so lesser the load lesser the velocity.
Colder basal water temperature will generate less amount of melt as compared to warmer basal water temperature, so in colder condition, glacial flow velocity will not be increased.
What first comes to my mind is that one or more rivers feature very prominently in these civilizations: the Nile in the Egyptian and the Tigris and Euphrates in the Babylonian.
I think that it was a siege
