Flooding happens when heavy rainfalls and the ground is unable to drain the water fast enough. Most plants can withstand flooding which doesn’t last for long (unless it is a severe torrential flood that washes away everything in its path), but prolonged flooding can cause great damage to crops. In many areas, floods are happening more often, or with greater severity. It is important that crops are protected from flooding, particularly in areas that are vulnerable to flooding.
There are many things we can do to help water drain from the soil and to reduce damage to crops:
Planting trees in upland areas and keeping the soil covered
Planting trees in upland areas reduces run-off times.
When the soil is not covered by vegetation, mulch, or crop residues, it will be more exposed to the impact of rainfall.
When the soil is protected by mulch, adjacent trees and shrubs, or cover crops (these are usually leguminous crops such as pigeon peas, lablab, velvet beans), the water flow is slowed down, so the water has more time to infiltrate into the ground rather than run off the land, washing away high nutrient soil with it.
Build dikes to protect crops from floods
Dikes are barriers or walls built to protect the land from water damage.
They can be built using soil, stones, rocks, sandbags, or wood.
Properly built, dikes can protect crops from flooding.
A dike can slow water flow (for example, if made of stone) or divert water (in the case of clay or concrete dikes), or direct water flows to specific crops or other locations such as an irrigation channel.
Dikes will also help to prevent the loss of topsoil when there is heavy rainfall. If using soil to make dikes, it needs to be high clay content sub-soil, preferably on top of a stone base.
Clay soil should be compacted thoroughly to ensure that water does not breakthrough.
Sand bags or wire netting could be used to reinforce the dike, giving it more strength.
Grass could be planted on the dike to slow down erosion.
Plant flood-tolerant varieties of crops
Plant crops that are tolerant to flooding.
Most root vegetables are naturally flooding tolerant, and varieties of crops such as wheat and rice are being developed to be more resistant to floods.
Improve the drainage of land before planting crops that do not grow well with too much water
Crops can be grown in raised beds, on ridges, or on mounds to improve drainage. Ridges help to drain excess water, keeping it away from the plants.
Excess water can be drained if there is somewhere for it to go, or a storage pond could be dug at the lowest part of the garden/farm to store surplus water and allow it to soak into the subsoil slowly.
The pond should be filled with stones or gravel to prevent mosquito breeding. Ridges can be made using oxen- or donkey-drawn ridges or using hand hoes.
The distance between ridges varies from crop to crop and is also affected by the soil type. As an example, ridges can be made 60cm apart for planting maize. The depth can be up to 30cm but again will depend on the soil type and slope.