Drainage

Question 1

Key components of Drainage Design and Construction

Answer 1

1. Hydrology: Study of water flow, rainfall, and run-off patterns.
2. Hydraulics: Design of channels, pipes, and structures to efficiently convey water.
3. Geology: Consideration of soil, rock, and groundwater conditions.
4. Topography: Evaluation of land slopes, elevations, and contours.
5. Environmental Impact: Minimizing effects on ecosystems and water quality.
6. Surveying and Mapping: Accurate surveying to determine boundaries, elevations, and drainage patterns.
7. Materials Selection: Choosing suitable materials for drainage structures, like pipes and concrete.
8. Construction Methods: Selecting appropriate techniques such as trenching and excavation.
9. Safety Considerations: Identifying and mitigating potential hazards like flooding and erosion.
10. Maintenance and Operation: Planning for ongoing maintenance, including inspection and repair of the drainage system.

Question 2

Types of Drainage Systems

Answer 2

1. Surface Drainage: Manages water on the surface using gutters, down spouts, and storm drains. Common in urban areas, parking lots, and roads.
2. Subsurface Drainage: Directs water underground using pipes, culverts, and French drains. Often used in agricultural fields, landscaping, and foundation drainage.
3. Urban Drainage: Designed for cities, focusing on storm water management, flood control, and water quality improvement.
4. Rural Drainage: Manages water in agricultural and natural areas using ditches, canals, and tile drainage systems. Aims to prevent erosion, reduce flooding, and maintain water quality.
5. Highway and Road Drainage: Designed for roads and highways to prevent hydroplaning and flooding, protect pavement durability, and ensure water quality. Uses culverts, catch basins, and guardrails.
6. Building and Foundation Drainage: Protects buildings and foundations from water damage using footing drains, sump pumps, and gutter systems. Essential for maintaining structural integrity.

Question 3

Name and explain Construction Techniques Used in Drainage Systems

Answer 3

Name and explain Construction Techniques Used in Drainage Systems,
1) Excavation and Grading:
◌ Remove soil to create trenches.
◌ Grade terrain for proper water flow.
2) Pipe Laying and Trenching:
◌ Place pipes in trenches with proper alignment.
◌ Backfill trenches with soil or aggregate.
3) Channel and Culvert Construction:
◌ Build concrete or masonry channels.
◌ Install culverts to convey water under obstacles.
4) Storm water Management Facility Construction:
5) Tunnelling and Pipe Jacking:
6) Open-Cut and Cut-and-Cover Methods:
◌ Excavate trenches and cover them with slabs.
◌ Used for shallow systems like gutters.
7) Micro-Tunneling and Horizontal Directional Drilling (HDD):
◌ Use remote-controlled machines for small pipes.
◌ Drill and enlarge holes for pipe installation.
8) Erosion Control Measures:
◌ Use riprap, gabions, or geotextiles to prevent erosion.
◌ Protect channels and slopes from erosion.
9) Concrete and Masonry Construction:.
10) Green Infrastructure Installation:

Question 4

Best practices Construction Techniques Used in Drainage Systems

Answer 4

◌ Follow local regulations and standards.
◌ Conduct thorough site analysis and design.
◌ Use durable and sustainable materials.
◌ Implement erosion control measures.
◌ Regularly inspect and maintain systems.

Question 5

The arrangement of drainage system is governed by:

Answer 5

i. The internal layout of connections
ii. External pipe position
iii. Relationship between buildings.
iv. Location of public pipes.
v. Topography of the area.

Question 6

Gravity drainage design considerations

Answer 6

i. Pipe sizes
ii. Gradients
iii. Depth at which pipe is placed
iv. Geological considerations
v. Seepage

Question 7

Explain Sewage

Answer 7

Refers to waste matter from domestic or industrial areas that are carried in sewers or drainsVelocity of sewage affected by size of particles to convey and specific weight of particle.

Question 8

Explain Manholes

Answer 8

Shafts with removable covers that lead to sewers or drains through which a person can access. Often called inspection chambers.

Question 9

Where are Manholes Located at

Answer 9

Where are Manholes Located at:
 Changes in direction and gradient
 Junctions
 Head of each sewer
 Intervals not exceeding 100 m

Question 10

Name the Two Main Aspects of surface drainage

Answer 10

1. Hydrological Study: Focuses on the volume of water arriving at a ditch or culvert.
2. Hydraulic Design: the design of facility to handle the water.

Question 11

Runoff Coefficient (P): Proportion of water reaching a point after soakage and evaporation influenced by

Answer 11

o Soil infiltration
o The nature and extent of vegetation
o Length and steepness of slope
o Catchment size and shape
o Atmospheric temperature

Question 12

Channels

Answer 12

May be man-made or natural

Question 13

Advantages of Channels

Answer 13

Low construction cost
Large discharge
Useful for storage and recreational purposes

Question 14

Disadvantages of Channels

Answer 14

The space that is occupied
Require regular maintenance
Can be misused by people.

Question 15

Culvert

Answer 15

A conduit that conveys water through an embankment. May be precast reinforced units