CSLB C-27 Landscaping ContractorSite Preparation and DrainageMedium
A landscape contractor is designing a surface drainage system for a large, flat commercial parking lot. To ensure efficient water removal and prevent standing water, what is the minimum recommended longitudinal slope for a concrete swale or gutter in this application?
- A0.25%
- B1.0%
- C0.5%
- D2.0%
Show answer & explanationAnswer & explanation
Correct answer: C. 0.5%
For concrete swales or gutters in flat areas like parking lots, a minimum longitudinal slope of 0.5% is generally required. This ensures positive drainage and prevents water from pooling, especially important for hard, impermeable surfaces.
Why the other options are wrong
- A. 0.25% is generally too flat for concrete swales and can lead to standing water and debris accumulation.
- B. 1.0% provides excellent drainage but is not the minimum required; it may increase construction costs unnecessarily.
- D. 2.0% is a very effective slope but is often more than necessary for a swale and could be too steep for some applications.
Minimum Concrete Swale Slope
The minimum recommended longitudinal slope for concrete swales or gutters, typically 0.5%, to ensure positive surface drainage and prevent water accumulation on impermeable surfaces.
- Prevents standing water and debris buildup.
- Ensures continuous flow towards collection points.
- Critical for hard surfaces like parking lots and driveways.
- Steeper slopes increase flow velocity and potential for scour.
Memory trick: Half a percent, for concrete water sent.