Author: Donna Conneely
As floods become more frequent and much more severe, novel ways of fighting them are cropping up all over the world. In some cases, the “new” flood control techniques may be in fact a return to ancient practices that have been lost in recent times. This may be the case with the recent enthusiasm for the introduction (or re-introduction) of farming practices that can help prevent or reduce flooding in the towns and cities located nearby.
Farmers rely heavily on water for their livelihood. Too much water or too little water — both of these scenarios can spell disaster for those who produce our food supply. Some flood control engineers are advocating for a natural approach to water and soil conservation that will, it is claimed, provide reliable water for the farmers and help protect nearby communities from flooding.
The new measures call for several methods of flood control. One idea is to encourage farmers to allow some designated part of their land to be given over to flooding in the event of major precipitation rather than blocking the water — which would in many cases mean directing floods toward population centers. In this case, a farmer might permit some flooding of some cropland in order to protect more developed land. A bonus of this practice is that the flooded land becomes more fertile, having the benefit of alluvial deposits. Of course, in allowing some land to be given over to flooding, the farmer loses the productivity of that land for some time, so most localities are arranging for financial compensation for farmers who participate.
Another method of flood reduction is called conservation tillage. This practice entails simply leaving the fields covered with the stalks, roots, and other debris from last year’s crops. Something as simple as this can make a huge difference in the amount of runoff during storms and can greatly reduce the soil erosion that comes with it. There are many other benefits; including increasing rich organic matter in the soil, improving water and air quality, attracting beneficial earthworm colonies, and even providing sustenance and shelter for wildlife.
But the most important reward of conservation tillage is that it helps to hold water on the land. The stalks of the harvested crops, if left in place, provide shade on the land, preventing much of the evaporation that would occur on completely denuded fields. In addition, the stalks act as tiny dams during heavy rains, slowing the water long enough for it to soak into the ground rather than just running off the land. Wind erosion is also greatly decreased in these fields, and much less dust (and topsoil) flies off with the winds.
While all of these other benefits of conservation tillage may be of great value to farmers, food consumers, and earthworms; when it comes to preventing floods in nearby towns, the most important benefit of conservation tillage is the great reduction of “soil sealing”. Soil sealing is the result of raindrops hitting bare soil, a process that compacts the soil and makes it impermeable to water infiltration. Soil that has been compacted and sealed by hard rains will not easily absorb water, and the water will run off in the same way it runs off asphalt. Fields that are covered with stalks and old root systems will not suffer this compaction, and the water will be slowed down enough to sink into the permeable soil.
As climate change, harmful human activity, and rising sea levels all contribute to an increase in floods and major storms, we will need to change our practices on many levels to reduce the resulting destruction and damage. Conservation tillage is likely to become one of the many useful techniques borrowed from the past that will help ensure a better future.