Environmental Engineering and Stormwater Management Flashcards
6 cards from real Civil Engineering PE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Environmental Engineering and Stormwater Management flashcards as text
In the rational method Q = CiA, the variable i represents:
Answer: Rainfall intensity for a storm duration equal to the time of concentration
In Q = CiA, i is the design rainfall intensity (in/hr) corresponding to the time of concentration and the selected return period storm.
The NRCS Curve Number (CN) method estimates:
Answer: Direct runoff depth from storm rainfall depth
The CN method calculates direct runoff Q from rainfall P using Q = (P − 0.2S)²/(P + 0.8S), where S is the potential maximum retention based on CN.
Time of concentration (Tc) for a watershed is defined as:
Answer: Travel time from the hydraulically most remote point to the outlet
Tc is the travel time of runoff from the farthest point in the drainage area to the outlet, and it governs the critical storm duration for design.
A dry detention basin is designed primarily to:
Answer: Attenuate peak flows by temporarily storing runoff
Dry detention basins temporarily store excess runoff to reduce peak discharge rates, releasing water through a controlled outlet after the storm passes.
A typical Manning's roughness coefficient (n) for a natural earthen channel is:
Answer: 0.025–0.035
Natural earthen channels have n ≈ 0.025–0.035, considerably higher than smooth concrete linings (n ≈ 0.012–0.015).
Hydraulic radius R in Manning's equation is defined as:
Answer: Cross-sectional flow area divided by wetted perimeter
Hydraulic radius R = A/P, where A is the cross-sectional area of flow and P is the wetted perimeter; for a full circular pipe R = D/4.