Lesson 6: Fundamental Concept of Drainage

Question 2

The methods used for land drainage

Answer 2

surface drainage and subsurface drainage

Question 3

land surfaces are reshaped as necessary to eliminate ponding and establish slopes sufficient to induce gravitational flow overland and through channels to an outlet. Surface drainage may be divided into works which

Answer 3

surface drainage

Question 4

Ditches and buried drains are installed within the soil profile to collect and convey excess ground water to a gravity or pumped outlet. The drop in pressure resulting from discharge induces the flow of excess ground water through the soil into the drains.

Answer 4

subsurface drainage

Question 5

Are used to prevent entry upon the land when ground water moves laterally. Drains are oriented approximately at right angles to the direction of ground-water flow.

Answer 5

Interceptor drains

Question 6

Used when land surfaces are nearly flat, flow velocities low, or interception of ground water ineffective. Drains are commonly (but not necessarily always) oriented approximately parallel with the direction of ground-water flow

Answer 6

Relief drains

Question 7

Design criteria are developed in two general ways:

Answer 7

from empirical data collected through evaluation of existing drainage systems, and (b) from a theoretical analysis of the problem, applying known physical laws and testing the theory through evaluation of existing drainage systems.

Question 8

Describes the process of removal of that water which has infiltrated into the soil in excess of the amount that can be held by capillary forces against the force of gravity.

Answer 8

Subsurface drainage

Answer 9

Basin-type free-water table

Answer 10

Water table over an artesian aquifer

Answer 11

Perched-water table

Answer 12

Lateral ground-water flow problems