2102 - Soil Drainage

Question 1

Symptoms of Poor Drainage

Answer 1

Water Table Fluctuates and generally will be higher in winter than summer. Survery sites in both dry periods and wet to determine the needs for drainage.

Wet Periods

• Surface Water
• Areas of soil that remain Boggy after heavy rain

Dry Periods

• Indicator Plants, Salix spp. Ranunculus spp. suggestive of poor drainage.
• Poor plant growth.

In the soil profile

• Gleyed Soil, where Oxygen is in short supply.
• Poor Root Development, not extensive and may be shallow and horizontal.

Question 2

Removing Excess Water methods

Answer 2

Drainage Systems - Surface or Sub-Surface, include piped or pipeless systems.

French Drain - Basic Pipeless drainage trench

Soakaway - Gravel filled pipe which excess water runs into. Proximity to buildings is regulated by local authorities.

Mole Ploughing - Drawn through the soil to make a sub surface channel for the water to flow through. Not suitable for all soils, or on a small scale.

Sub-Soiling - Breaking open Soil Surface Pan, allowing water through to the main water table.

Plant Selection - Right Plant Right place, Bog or Marginal plants. Carex pendula, Lobelia cardinalis

Question 3

Raised bed

Answer 3

Circumvent soggy sites, particularly if you would want to grow vegetables. Good for small scale alternative.

Question 4

French Drain

Answer 4

Channel dug with cambered walls, layered with Geo Textile to allow water access but stop soil erosion.
Filled with (shingle) 20mm gravel and covered with decorative gravel.

Question 5

Outfall

Answer 5

An exit point of a drainage system, eg. ditch/channel

storm drain, ditch or soakaway

Question 6

Soakaway

Answer 6

Gravel filled pipe which excess water runs into. Pipe drainage can be directed into a soakaway when there is no other Outfall available.

Question 7

Benefits of improving drainage

Answer 7

Improved microbial activity thus improved nutrient availability
Increased Oxygen access for plants and organisms. Thus healthier roots and plants.
Better anchorage for plants.
Roots will go deeper, so will be more resilient to drought.
Soil warms faster, prolonged growing season.
Less risk of disease

Question 8

Irrigation Methods

Answer 8

Watering Can
Hose
Sprinklers
Drip Lines

things to consider - Timing and Watering Depth