FDOT Drainage and Stormwater Management 3 — Questions and Answers
Question 1: What is the minimum required freeboard above the 100-year flood elevation for FDOT roadway design?
- 0 feet — roadway can be at 100-year elevation
- 1 foot (Correct answer)
- 2 feet
- 3 feet
Correct answer: 1 foot
FDOT requires a minimum of 1 foot of freeboard above the 100-year flood elevation for roadway design to provide a safety margin.
Question 2: What Manning's roughness coefficient (n) does FDOT typically use for smooth concrete pipe in hydraulic calculations?
- 0.010
- 0.012 (Correct answer)
- 0.015
- 0.024
Correct answer: 0.012
FDOT uses a Manning's n of 0.012 for smooth concrete pipe in hydraulic calculations, reflecting the pipe's relatively smooth interior surface.
Question 3: According to FDOT specifications, what is the maximum joint gap allowed between sections of reinforced concrete pipe during installation?
- 0.5 inch
- 0.75 inch
- 1 inch (Correct answer)
- 1.5 inches
Correct answer: 1 inch
FDOT allows a maximum joint gap of 1 inch between reinforced concrete pipe sections to ensure adequate soil support and prevent joint failure.
Question 4: What is the primary purpose of a detention pond (versus a retention pond) in FDOT stormwater design?
- Permanently store water indefinitely
- Temporarily store excess runoff and release it at a controlled rate (Correct answer)
- Treat water through biological processes only
- Infiltrate 100% of runoff into groundwater
Correct answer: Temporarily store excess runoff and release it at a controlled rate
Detention ponds temporarily hold excess stormwater and release it slowly through a control structure, reducing peak discharge rates to receiving waters.
Question 5: What FDOT standard index drawing covers inlet types and dimensions for stormwater collection?
- Index 201
- Index 232
- Index 425 (Correct answer)
- Index 601
Correct answer: Index 425
FDOT Index 425 covers drainage structure inlet types, dimensions, and construction details used in stormwater collection systems.
Question 6: In FDOT drainage design, what does the rational formula variable 'C' represent?
- Catchment area in acres
- Rainfall intensity in inches per hour
- Runoff coefficient based on land use (Correct answer)
- Time of concentration in minutes
Correct answer: Runoff coefficient based on land use
In the rational formula Q = CiA, the variable C is the dimensionless runoff coefficient that represents the fraction of rainfall that becomes runoff based on land use and soil type.
FDOT Drainage and Stormwater Management 3
What is the minimum required freeboard above the 100-year flood elevation for FDOT roadway design?