1. The main purpose of a stormwater drainage system is to:
(A) Supply water to households
(B) Treat sewage
(C) Collect and convey rainwater from streets and roofs to prevent flooding
(D) Store water for irrigation
2. The type of storm sewer that collects water from streets and discharges it into a main sewer is called:
(A) Lateral sewer
(B) Trunk sewer
(C) Interceptor sewer
(D) Combined sewer
3. The minimum velocity of flow in a storm sewer to prevent silt deposition is generally:
(A) 0.3 m/s
(B) 0.6 m/s
(C) 1.0 m/s
(D) 1.5 m/s
4. Catch basins in stormwater drainage are used for:
(A) Storing stormwater
(B) Allowing sediment to settle before water enters the sewer
(C) Measuring flow
(D) Diverting sewage
5. The maximum spacing of catch basins on a street is usually:
(A) 50 m
(B) 90 m
(C) 120 m
(D) 150 m
6. The design of stormwater sewers is usually based on:
(A) Average annual rainfall
(B) Dry weather flow
(C) Minimum rainfall intensity
(D) Peak storm intensity and duration
7. The rational method is used to:
(A) Determine sewer slope
(B) Calculate peak discharge from a drainage area
(C) Design pipe thickness
(D) Estimate sewer material strength
8. In the rational method, the formula Q = CiA, “C” represents:
(A) Runoff coefficient
(B) Catchment area
(C) Rainfall intensity
(D) Flow velocity
9. The runoff coefficient “C” depends mainly on:
(A) Soil type, land slope, and land use
(B) Sewer diameter
(C) Rainfall intensity
(D) Pipe material
10. A combined sewer system carries:
(A) Only stormwater
(B) Only sewage
(C) Both sewage and stormwater
(D) Treated water
11. The time of concentration in stormwater design is:
(A) The time taken by water to reach the nearest river
(B) Time required for sediment deposition
(C) Duration of rainfall
(D) Time taken for runoff to travel from the most distant point of the drainage area to the outlet
12. A stormwater detention basin is provided to:
(A) Treat wastewater
(B) Store stormwater temporarily to reduce peak flow
(C) Increase runoff velocity
(D) Measure rainfall
13. Open channels are preferred over closed conduits when:
(A) There is limited land
(B) Flow is low and gradient is steep
(C) Flow is high and debris-free
(D) Pipes are cheaper
14. The slope of a stormwater sewer is generally designed to:
(A) Allow self-cleansing of silt
(B) Reduce construction cost
(C) Maximize storage
(D) Slow down flow
15. In urban areas, stormwater drains are usually designed for:
(A) 2-year storm return period
(B) 5-year storm return period
(C) 10- to 25-year storm return period
(D) 50-year storm return period
16. A curved sewer is preferred in stormwater design when:
(A) The sewer has to follow street alignment
(B) Flow velocity is very low
(C) To reduce sediment deposition
(D) High pressure is required
17. Catch basins should be designed to remove:
(A) Large debris only
(B) Sand and silt from stormwater
(C) Dissolved salts
(D) All chemical pollutants
18. Retention ponds in stormwater management are mainly used to:
(A) Convey water rapidly
(B) Generate electricity
(C) Store water and allow sedimentation
(D) Recharge groundwater only
19. The minimum diameter for a circular storm sewer in urban areas is usually:
(A) 150 mm
(B) 300 mm
(C) 450 mm
(D) 600 mm
20. Trunk sewers are designed to:
(A) Collect flows from lateral sewers and convey them to the outfall
(B) Serve individual houses only
(C) Store stormwater
(D) Prevent soil erosion
21. Velocity in stormwater sewer should not exceed:
(A) 0.5 m/s
(B) 5 m/s
(C) 10 m/s
(D) 15 m/s
22. Hydraulic grade line in sewer design represents:
(A) Flow rate
(B) Depth of water
(C) Energy level of the flow
(D) Slope of sewer
23. Culverts are provided in stormwater drainage for:
(A) Crossing under roads or railways
(B) Water storage
(C) Sediment removal
(D) Irrigation
24. Stormwater pumping stations are required when:
(A) To measure discharge
(B) Flow is very small
(C) For water treatment
(D) Gravity flow is insufficient to convey stormwater
25. Rooftop drains are connected to:
(A) Sewer trunk only
(B) Stormwater drains or collection system
(C) Septic tank
(D) Groundwater recharge pits
26. Runoff from impervious surfaces is generally:
(A) Less than pervious surfaces
(B) Equal to pervious surfaces
(C) More than pervious surfaces
(D) Negligible
27. The rational formula Q = CiA is applicable for drainage areas:
(A) Less than 200 hectares
(B) More than 1000 hectares
(C) Only rural areas
(D) Only for rivers
28. Self-cleansing velocity is the minimum velocity required to:
(A) Prevent pipe collapse
(B) Increase pipe diameter
(C) Avoid sediment deposition
(D) Improve groundwater recharge
29. Concrete channels in stormwater drainage are preferred for:
(A) High sediment load areas
(B) Low flow velocities
(C) Rural areas only
(D) Vegetated areas
30. The primary factor affecting stormwater runoff is:
(A) Pipe material
(B) Sewer diameter
(C) Pipe slope
(D) Soil permeability