B. urbanization increases/decreases (highlight one) the lag time between rainfall and peak stream flow. (1 pt)
c. compare the two stream flow curves. urbanization increases/decreases (highlight one) the period of time over which runoff occurs. (1 pt)
d. explain why during intense rainfall urban areas often experience the flash flooding conditions you noted in questions a-c. (2 pts)

explained below.

Explanation:

b) Urbanization decreases  the lag time because the  loss of the rainfall decrease as the water absorbed by the ground decreases and water reaches to the river very quickly.

c) In urbanization the runoff occurs for small period of time because there is no hindrance in the flow of the rainfall so the runoff reaches very quickly to the water body.

d) Intense rainfall in urban area often experience the flash flood condition because there no absorption of water by the ground, trees are less so which does not lead to perception of water by leaves of the tree hence all the rainfall is basically converted into runoff and city does not have system to act on the situation which lead to flash flood condition.