Question

a.For a single severe rainfall event, what are the four components or fates at the start of the hydrologic cycle? Which two capture the most rain or snow at the early stages of the event, and what happens to it?

b. A storm t_d = 2 hrs. Rain intensity is steady i = 1.0”/hr. The infiltration rate quickly stabilizes at f= 0.25”/hr. How many inches infiltrate over 2 hours?

c. List the benefits of directing roof runoff to an infiltration bed, and also, the risks. Why would a surface infiltration bed probably perform longer than an underground one?

Answer 1

a) The four components at the start of rainfall of hydrological cycle are

1) Precipitation

2) Infiltration

3) Percolation

4) Runoff

Precipitation is the rainfall or snow that causes the moisture in air to fall as rain. Infiltration is the process in which the water infiltrates through buildings and trees and reaches the ground surface.The water which reaches the ground surface percolates through the soil and it constitutes as ground water.Run off constitutes for the flow of water in rivers and streams.

b) Given that the rate of infiltration of water is 0.25 in/hr

Rate of rainfall = 1 in/hr

Rate of rainfall > rate of infiltration

Hence rain water will infiltrate at the rate of 0.25 in/hr for the rainfall duration of 2 hours

Hence total infiltration = (2)*(0.25) = 0.5 inches in 2 hours

Total infiltration = 0.5 inches

c)

1)The benefit of directing runoff to the infiltration beds is the runoff to the municipal rainfall sewers can be reduced and the rain water can be harvested for future use.

2)The underground water table level can be improved by directing the water to the underground infiltration beds

3)The risks associated with the infiltration beds is since they hold the moisture they might pose a risk of water logging and the area might become damp.

4)Surface infiltration beds can perform longer than the underground infiltration beds because surface infiltration beds are easily accessible and could be easy to maintain compared to underground beds and excess water in the surface filtration beds can undergo evaporation and prevent it from water logging