LARE LARE Drainage System Design 2

Question 1

Which hydraulic concept describes the condition when stormwater runoff exceeds the infiltration capacity of the soil?

Accepted Answer

Horton overland flow

Answer

Horton overland flow occurs when rainfall intensity exceeds the soil's infiltration capacity, causing surface runoff.

Question 2

In a bioretention cell, what is the primary purpose of the ponding zone?

Accepted Answer

To provide temporary storage for incoming stormwater before it infiltrates

Answer

The ponding zone temporarily stores stormwater above the growing media, allowing it to infiltrate gradually.

Question 3

A designer needs to reduce the peak discharge from a 10-year storm. Which approach directly addresses this goal?

Accepted Answer

Installing a detention basin with a controlled outlet

Answer

A detention basin stores runoff and releases it at a controlled rate, reducing peak discharge to downstream systems.

Question 4

Which Manning's roughness coefficient (n) value best represents a clean, straight natural earth channel?

Accepted Answer

0.025

Answer

A clean, straight natural earth channel typically has a Manning's n of approximately 0.025.

Question 5

What is the primary regulatory intent of the water quality volume (WQv) standard in stormwater design?

Accepted Answer

To capture and treat the first flush of stormwater runoff containing the highest pollutant loads

Answer

WQv standards target the first flush — typically the first 0.5–1 inch of runoff — which carries the greatest pollutant concentrations.

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