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Farm Flooding

HOW TO MANAGE FARM FLOODING

Floods can be a cause of severe difficulty to the farmer. Excess rainwater run-off can result in erosion and loss of valuable topsoil. Conversely sediment laden flood water can deposit valuable soils and nutrients as water levels drop. Floods can also cause severe losses through:

  • Death, or reduction in health of stock.
  • Damage to fencing and structures (e.g. sheds, bridges).
  • Temporary reduction in area for stock to graze.
  • Poor conditions for trafficking and/or cultivation (e.g. boggy) for stock and machinery.

The pathway that water takes when it reaches a stage of overflow is directly controlled by gravity. We can therefore always predict which way is the most efficient path that water will select but we sometimes have problems with predicting the quantity of that flow.

This is when we have problems and flooding and erosion occur.

Due to the unpredictable atmospheric nature, it is very likely that we will never be able to forecast weather with 100% accuracy due to a factor known as the chaos theory. In short what the chaos theory implies is that the mathematics required to accurately predict weather are so enormous that even by using a super computer one thousand times more powerful than today's technology to factor in all known variables by the time you had received an answer, the original conditions would have changed to such a large extent to warrant any accuracy to the result. We certainly can predict with a good deal of accuracy most weather conditions due to region and seasonal history but never the absolute maximum severity or exactly where it will strike.

Engineers of course don't sit around feeling beaten; they have in fact developed minimum safety guidelines for buildings and community infrastructure (such as roads and drainage systems) that are developed on statistical probability. In this manner 95 percent of the effects of a severe deluge would be dealt with almost immediately and only in very extreme circumstances are there going to be system foul ups. Weather, however, is not the only eventuality that can cause problems with water. How do we cope when the systems themselves malfunction or are involved in an accident?

The ability of a drainage system to cope with emergencies is often a very real reflection of the engineer who designed and planned it. A good system will always have safety devices built into the basic design. Cost may be a limiting factor in design but so too is poor design and, often with a little thought, big problems can be made manageable with careful, thought out, design processes.

Rainfall

Often rainfall causes problems because of a lack of consistency. In the case of too much rainfall (which may sometimes lead to soil saturation) suitable drainage is needed to disperse the excess. In terms of saturation, it is very important to understand the relationship and dynamics that may occur between water and soil to understand the management of drainage and irrigation processes.

Excess rain may either lay on the surface of the ground or it may water-log the root area of what’s being harvested. The water may enter the soil either by uncontrolled rainfall or irrigation practices, and the rate at which water enters the soil (Infiltration Rate) will depend on the texture of the soil (i.e. slower in clay and faster in sandy soils) as well as its “moisture status” (i.e. if the soil is already dry or moist at the time the water hits the soil). All this may help us understand and determine the importance of having a good draining base or installing sub-soil drains and decide the right type of drainage required.

Minimizing the Flood Risk 

There are some simple means by which flood damage can be minimised. These include:

  • Ensuring that any structures such as sheds, shelters, food (i.e hay and silage) are located, where possible, as high as possible above known natural flood plains.
  • Soil that has vegetative cover will always stand up to flood better than bare ground.

Overgrazing, or cultivating soil at times of the year when floods are likely will increases the potential for soil loss if flooding occurs.

  • If possible arrange fencing of low lying areas to include if possible a few areas where stock can retreat to as water rises, if needed.
  • Have a procedure for evacuating stock in case of flood, including: having suitable transport available (boats may be necessary in regularly flooded areas). Having a suitable place to take stock too, and temporary provision for food, shelter and water.
  • Regular monitoring of flood levels - don’t leave things too late to act.

UNDERSTAND MORE ABOUT FARM FLOODING

If you work on a farm or manage a farm, learn with ACS to improve your knowledge and skills - learn about soil management, irrigation and much more, we offer a great range of Agriculture Courses to choose from - see the links at the bottom of this page.

Do you want to know more? We will be pleased to help - phone us today on (UK) 01384 442752 / (International) +44 (0) 1384 442752 - or get in touch with our Agriculture specialists.

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