Soil Structural Degradation In England And Its Affects On Runoff And Flooding

Flooding soil run off Kemble Thames source

Field investigations between 2002 and 2011 identified soil structural degradation to be widespread in SW England with 38% of the 3243 surveyed sites having sufficiently degraded soil structure to produce observable features of enhanced surface-water runoff within the landscape. Soil under arable crops often had high or severe levels of structural degradation. Late-harvested crops such as maize had the most damaged soil where 75% of sites were found to have degraded structure generating enhanced surface-water runoff. Soil erosion in these crops was found at over one in five sites. A tendency for the establishment of winter cereals in late autumn in the South West also often resulted in damaged soil where degraded structure and enhanced surface-water runoff were found in three of every five cereal fields. Remedial actions to improve soil structure are either not being undertaken or are being unsuccessfully used. Brown Sands, Brown Earths and loamy Stagnogley Soils were the most frequently damaged soils. The intensive use of well-drained, high quality sandy and coarse loamy soils has led to soil structural damage resulting in enhanced surface-water runoff from fields that should naturally absorb winter rain. Surface water pollution, localised flooding and reduced winter recharge rates to  result from this damage. Chalk and limestone landscapes on the other hand show little evidence of serious soil structural degradation and <20% of fields in these landscapes generate enhanced runoff.




Water Movement In Soils

A good little video showing different aspects that affect how well a soil manages the water that falls on it,  will it run off or move down into the soil. Will it have a negative impact with run off and flooding or will it have a positive impact on plants and aquifers.

Altough only an introduction it touches on things such as soil compaction, drainage, leaching, capillary action in unsaturated soils, gravity as the dominant force that moves water downward in saturated soils. The soils texture and structure, platy, prismatic, columnar, granular, and blocky soils. Percolation rates and pore sizes etc


How To Really Stop Flooding


When soil is depleted of organic matter, water just runs off it. A rethink of farming practice is much more vital than dredging or barriers.

The Prince of Wales’s visit to the Somerset Levels has once more drawn attention to the dire circumstances faced by thousands of people because of floods. And as more extreme rain drenches the UK, calls for more flood defences and river dredging have predictably become louder. There is, however, another focus that has been hardly mentioned. It’s soil or, more specifically, the benefits we could gain by treating it better.

The way we use land has fundamentally altered the way that many of our soils work. Intensive cultivation and grazing cause massive soil loss, with sediments leaving fields to clog up watercourses. Machinery and animal hooves have also caused many soils to become compacted so that, instead of absorbing water, holding it and slowly letting it go, it runs off hard impermeable surfaces all at once.

Because of intensive farming reliant on inorganic fertilizers, there has also been a widespread reduction in the proportion of soils comprising decaying plant remains – the so-called organic matter. Soils depleted in this way hold less water than when they have a healthier proportion of once living material, thereby further altering their ability to ameliorate flood risk.

Continue reading “How To Really Stop Flooding”

Easter Islands Ancient Gardening Practices

A few short segments from a documentary about Easter Islands (Rapa Nui) and how it become to be deforested and baron. The ancient Rapanui people did abuse their environment but they were also developing sustainable practices—innovating, experimenting, trying to adapt to a risky environment. They are generally held responsible for cutting down 6,000,000 trees in 300 years (though that is disputed), for example they were also developing new technological and agricultural practices along the way—such as fertilization techniques to restore the health of the soil and rock gardens to protect the plants. “Societies don’t just go into a tailspin and self-destruct,” says Stevenson, an archaeologist at the Virginia Department of Historic Resources. “They can and do adapt, and they emerge in new ways. The key is to put more back into the system than is taken out.”

This section of the documentary caught my attention due to this being the first time hearing about “lithic mulching” which is basically putting down rocks to help prevent soil erosion by creating micro climates with rocks, this helped create shade and deterred weeds too. Also not mentioned here is how these volcanic rocks would have eroded down remineralising the soil as they went. Other gardening practices show them growing fruit in caves entrances for shade from elements and building “manavai” stoned circle walls to protect plants from salt winds etc”

This next clip shown above speaks about how the practices of the inhabitants of the island were sustainable. They go on to show a possible indication of water conservation showing gulleys, dams, pavements and what effectively looks to me as water retention, encouraging the water to soak in to stop runoff in heavy rains. Well that or maybe they are “water gardens” or some kind of ancient method of “plumbing” water. They also show how as well as cuttings down tree’s they planted them too.

Several interesting gardening practices some of which today we maybe could call experimentations in “permaculture”.

Original Name: Easter Island Mysteries of a Lost World
Detail: S01E01
Copyright: BBC4