BLArch Bachelor of Landscape Architecture Grading and Drainage 1 — Questions and Answers
Question 1: What is the minimum recommended slope away from a building foundation to ensure positive drainage?
- 0.5% for 5 feet
- 1% for 10 feet
- 2% for 10 feet (Correct answer)
- 5% for 20 feet
Correct answer: 2% for 10 feet
A minimum 2% slope (2 inches of fall per 10 feet) away from building foundations is the standard to direct water away and prevent infiltration.
Question 2: In landscape grading, what does the term 'spot elevation' refer to?
- The highest point on a grading plan
- A specific elevation noted at a precise point on a plan (Correct answer)
- The average elevation of a graded area
- The elevation of a drainage inlet
Correct answer: A specific elevation noted at a precise point on a plan
A spot elevation is a specific elevation value noted at a precise location on a grading plan, used to define critical high and low points.
Question 3: What is the formula for calculating percent slope?
- Rise ÷ Run × 100 (Correct answer)
- Run ÷ Rise × 100
- Rise × Run × 100
- (Rise + Run) ÷ 100
Correct answer: Rise ÷ Run × 100
Percent slope = (Rise ÷ Run) × 100, where rise is the vertical change and run is the horizontal distance.
Question 4: Which type of drainage system collects surface runoff through underground perforated pipes?
- French drain (Correct answer)
- Swale
- Catch basin
- Bio-retention cell
Correct answer: French drain
A French drain uses perforated pipe surrounded by gravel to collect and redirect subsurface or surface water away from problem areas.
Question 5: A 'swale' in site drainage is best described as:
- A vertical retaining structure
- A shallow, vegetated channel that conveys stormwater (Correct answer)
- An underground cistern for water storage
- A permeable paving system
Correct answer: A shallow, vegetated channel that conveys stormwater
A swale is a shallow, gently sloping, vegetated channel designed to slow, filter, and convey stormwater runoff across a site.
Question 6: What does the term 'cut and fill' mean in site grading?
- Removing topsoil and replacing subsoil
- Balancing excavated material (cut) with areas that need fill to minimize hauling (Correct answer)
- Cutting tree roots and filling with concrete
- Creating level terraces using retaining walls
Correct answer: Balancing excavated material (cut) with areas that need fill to minimize hauling
Cut and fill balances the volume of soil excavated from high areas (cut) with soil needed to raise low areas (fill), minimizing off-site hauling.
BLArch Bachelor of Landscape Architecture Grading and Drainage 1
What is the minimum recommended slope away from a building foundation to ensure positive drainage?