This house sits on the top of a hill that is covered with loose soil and rocks. The new owners of this house have some concerns about their property. What problems could they have because of erosion?

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Now that you have discussed the possible problems that erosion creates, use the information in the following slides to find ways to save this house and the property around it from soil erosion.

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Soil Horizons Levees

Terracing

Coastlines and Erosion

Barriers to Erosion

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Soil Erosion and Conservation

Go outside to a park, a field, or in the woods and you will find soil. Look where you see plants and trees and, again, you will find soil. Soil doesn’t just appear over night. It’s a slow change process where rocks and minerals are slowly weathered and broken down into small pieces. These pieces are then mixed with organic materials like trees, leaves, branches, twigs, dead and decaying animals, and animal waste. This mixture provides us with a valuable resource that we depend on throughout our lives.

Introduction

HUMUS

TOPSOIL

SUBSOIL

PARTLY WEATHERED

ROCK

Humus is the top layer of soil made mainly of decayed plants, animals, and animal waste. The topsoil is generally loose and rich with minerals that plants need to thrive. The subsoil contains clays and some topsoil. Water typically washes some minerals down into the subsoil. Beneath the soil is a layer of rock that has been partially broken and weathered and, over time, layered over by soils and decaying plant and animal matter.

Soil

Look closely and examine the topsoil and subsoil layers. In this picture you can see how the roots from the vegetation are growing down into the soil. The vegetation acts like a glue and holds the soil together. If you pull a handful of grass from the ground, you’re sure to get a clump of soil to go with it. This is further proof that vegetation holds soil together preventing unwanted erosion.

Plants and Erosion

Crops are grown on this farm. Notice the river that flows through the farm land. What possible dangers could this river cause?

Crops

River

Levee

Subsoil

Side View

Top View

Levees 1

As heavy rains fall and flood creeks and streams, local rivers will flood. These rivers can not be controlled and may flood the surrounding farm land, putting crops and lives in danger.

Crops

River

Levee

Subsoil

Side View

Top View

River at Flood Stage

River at Flood Stage

Levees 2

In order to prevent further flood damage and dangers, a levee (like a wall) is constructed to protect the land and people near this river. These levees are built of rocks and soil that help control the river in times of flooding.

Crops

River

Levee

Subsoil

Side View

Top View

Levees 3

As the rain falls and the river floods, the levee provides protection. By containing the river, the levee protects both farm land and lives. These levees are built in places not only to protect farms, but also along flood plains like those on the Mississippi River and in cities like New Orleans.

Crops

River

Levee

Subsoil

Side View

Top View

River contained at flood stage

River contained at flood stage

Levees 4

Over many years humans have adapted to use the land and soil around them. This picture illustrates how terraces are used to create farm land and conserve soil. As rain falls, water collects on each terrace, or step, rather than flowing down hill by gravity. This soil conservation method prevents soil from being eroded and provides people with farmable land. The diagrams above show how the land had to be altered before it could be successfully used in farming.

BEFORE TERRACING AFTER TERRACING

Terracing

Here you can see how ocean waves pound against the rocky coast. Ocean currents create crashing waves that collide against the rock, breaking and weathering the rock bit by bit. As each piece of rock is broken, it is then washed out to sea where it rests on the ocean floor.

Coastal Erosion

Crashing ocean waves repeatedly hit the coastline causing rock and sediment to be broken and weathered, then washed out to sea. Here you can see the waves have come in, pounded against the land, and retreated back to the ocean.

Wave Erosion

Each time the wind blows grains of sand are pushed from one place to another. Initially this push only affects small areas, but over months or years, the sand piles up in other places such as deserts and beaches.

Rain and moving water have a great impact on the erosion of sand and broken rock, but wind also plays a major role in erosion. Here you can see how grains of sand have been moved about by only wind. Over time this sand may come in contact with a barrier and build to form a dune. Or the sand may be moved from place to place until it is eventually washed into a stream, river, or the ocean. This is an example of how the natural agent, wind, produces slow changes on the earth’s surface.

Wind Erosion

This fence was constructed along a beach to prevent the dunes from eroding. Dunes that lie near coastlines are used to protect the land from wave surges that could cause great damage to cities and towns near the coastline. Here you can see how a fence was constructed to help prevent wind from eroding the dune. If this fence was not in place, the dune would be subjected to both wind erosion and wave erosion.

PreventingBeach Erosion

Examine this image. Do you notice where water flows down this slope during heavy rains? Special barriers have been constructed to prevent soil erosion. As heavy rains pour and water begins to flow down hill, the barriers stop the soil from being carried away.

Barriers to Erosion

Here you can see how rocks and boulders have been placed on the sides of the stream to prevent further erosion. The rocks and boulders stabilize the soil and keep it in place during times of high water and flooding.

Riprap and Rivers

Riprap is stone that has been placed on slopes to control erosion. It is frequently used to control erosion on a slope. In the pictures below you can see where riprap has been placed. The picture on the left show how riprap is used to stabilize the land when laid in storm water drainage areas. The picture on the right illustrates how riprap was placed on a stream bank to prevent further soil erosion.

Riprap