CSM Urban Stormwater Systems & Infrastructure Flashcards
6 cards from real CSM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 CSM Urban Stormwater Systems & Infrastructure flashcards as text
What is the 'first flush' phenomenon in urban stormwater management?
Answer: The disproportionately high pollutant concentrations found in the initial portion of stormwater runoff at the beginning of a storm event
The first flush refers to the phenomenon where the initial runoff from an impervious surface carries the highest concentrations of accumulated pollutants such as oil, heavy metals, and nutrients, often representing a disproportionate share of the total pollutant load.
What is peak flow attenuation in stormwater management and why is it important?
Answer: The reduction of the maximum rate of runoff discharge from a site to reduce downstream flooding and channel erosion
Peak flow attenuation reduces the maximum discharge rate from a developed site using detention or retention storage, protecting downstream channels and infrastructure from the increased runoff that development causes.
What is the Rational Method (Q = CiA) used for in stormwater design?
Answer: To estimate the peak runoff rate from a small drainage area based on rainfall intensity, drainage area size, and a runoff coefficient
The Rational Method estimates peak stormwater runoff rate (Q) as the product of the runoff coefficient (C), rainfall intensity (i), and drainage area (A), and is widely used for sizing storm drainage structures for small urban catchments.
What is a level spreader in stormwater management?
Answer: A structure that converts concentrated stormwater flow into sheet flow and distributes it uniformly across a vegetated filter strip
A level spreader is a constructed outlet structure that takes concentrated stormwater flow and spreads it as thin sheet flow across a vegetated filter strip or buffer, reducing velocity and improving infiltration and filtration.
What is Low Impact Development (LID) and how does it differ from conventional stormwater management?
Answer: LID uses distributed, small-scale practices integrated into the site design to manage runoff at the source; conventional approaches collect and convey runoff off-site in pipes
LID mimics the predevelopment hydrology by using decentralized practices like bioretention, permeable pavement, and rain gardens to infiltrate, evapotranspire, and harvest runoff at the source rather than routing it to a centralized pipe system.
What is the purpose of a trash rack or bar screen at a stormwater structure inlet?
Answer: To intercept large debris and prevent it from clogging or damaging downstream pipes, culverts, and outlet structures
Trash racks and bar screens at inlet structures catch large debris such as branches, trash, and leaves before they can clog pipes, damage pumps, or block outlet control structures.