Universal Soil Erosion Equation - ASU

1 Universal soil Erosion Equation Author: Laura Swantek Time: 50 minute class period Grade Level: 9-12. Background: soil is created by the weathering of rock and the decomposition of organic materials. Soils are classi- fied according to the amount of silt, sand or clay they contain. If the soil contains all three sediments, it is called loam and is modified by the word for the sediment of the highest concentration ( silty loam: loam with equal amounts of sand and clay but with more silt). soil forms very slowly and is necessary for sustain- ing life on earth. It is what our food is grown in! Erosion of this precious resource has been a problem since people first started farming during the Neolithic and continues to be a problem for farmers today.

2 Poor farm- ing decisions have already caused Erosion and desertification of million square miles of land. This has directly affected the food supply of 250 million people. Once land is cleared of trees and shrubs, it becomes more susceptible to Erosion , even if crops are planted in it. The Universal soil Erosion Equation can be used to determine how much Erosion by water will occur in specific areas. Using Erosion information from Neolithic and Bronze Age farming villages in Jordan, we can understand how scientists make sustainable farming deci- sions for the future. Objectives: 1- Students will be able to replace variables with numbers in a mathematical Equation and solve.

3 2- Students will be able to determine the rates of Erosion for different kinds of landscapes. 3- Students will be able to compare rates for different areas in order to determine which place would be the most sustainable to farm. 4- Students will understand how climate and the rate of Erosion influenced past farming decisions. 5- Students will understand that slowing the rate of Erosion through various methods will increase sustain- ability. 6- Students will be able to read slope, precipitation and soil maps generated with Geographic Information Systems (GIS) software and use the answers from the soil Erosion equations to locate sites on the map. Advanced Preparation: Print soil Erosion Equation worksheets Print soil , precipitation and slope maps Optional: print soil , precipitation and slope maps on transparencies that can be overlaid Materials: soil Erosion worksheets soil , precipitation and slope maps Medland Project introduction booklet Suggested Procedure: Introduction using the Medland Project booklet provided Read the introduction on the soil Erosion Equation worksheet together Students set up and solve equations and complete Erosion worksheet Students use the GIS generated maps of an area in Jordan to locate the two sites that were used for the equations Optional.

4 Using the transparencies and an overhead projector, show students how the GIS maps can be overlaid to give us a complete picture of the landscape Discuss soil Erosion and sustainability Mediterranean Landscape Dynamics Project Questions for Discussion How can events in the past help us make more sustainable decisions in the future? What can we do individually to make more sustainable decisions? Evaluation: Create a bar graph of the values for Cleared Flatland, Cleared Flatland using P factor, Cleared Hillside and Cleared Hillside using P factor in that order. Determine what happened to the numbers after a sustain- able farming method was used. Extensions: Students can change the values for some of the variables to see how they affect the rate of soil Erosion .

5 Is the government concerned about Erosion ? Find out what regulations have been implemented to control Erosion at Included at the end of the lesson is a Google Earth Snapshot of the part of Jordan the GIS maps repre- sent. This is the area within the red square. Using Google Earth software available free on the internet, students can use the latitude-longitude coordinates at the bottom of the snapshot to find this exact place by typing them into the find command. They can zoom in and see the real watershed the GIS maps show and how the slope map corresponds to what is actually on the ground. Resources: Dirt Poor, National Geographic article on the effects of soil Erosion on a population.

6 National soil Erosion Research Labo- ratory. Wikipedia article on sustainable agriculture. Arizona Standards Science Math Social Studies Inquiry Process Number Sense and Operations World History C3-PO1 C3-PO2 C1-PO7. History and Nature of Science Data Analysis, Probability and Discrete C9-PO4. C1-PO2 Mathematics C9-PO5. Science in Personal and Social C1-PO3 Geography Perspectives C1-PO8 C3-PO1. C1-PO1 Algebraic Representations C3-PO3. C1-PO3 C3-PO2 C4-PO6. C1-PO5 C4-PO7. C2-PO5 C5-PO3. C5-PO4. Mediterranean Landscape Dynamics Project Universal soil Erosion Equation Worksheet Beginning 10,000 years ago, during a period called the Neolithic, people started farming in Jordan.

7 Large groups of people lived together in lowland and hillside landscapes that they had cleared of trees and shrubs to create farmland. Around 8,000 years ago, the climate changed and more rain began to fall. People started living in much smaller groups (sometimes only 20 people) and farmed smaller areas because it was more sustainable. So, what happened that caused people to move to smaller villages? Later, during the Bronze Age, people adopted more sustainable farming techniques and lived in larger villages. We are going to use the Universal soil Erosion Equation to see if soil Erosion may have been a factor in the decisions made by early farmers about where to live.

8 After we determine Erosion rates, we are going to use maps to locate the archaeological sites that these numbers correspond to. soil Erosion Equation : A = KR(LS)C. A = Estimate of soil loss rate in tons/hectare/year K = soil erodibility factor R = Rainfall factor LS = Slope factor C = Crop management factor K Factor The K factor is based on the type of soil that is in the area you are investigating. soil can be composed of different types of sediment including sand, silt, and organic matter. These all erode at different rates. The soil in Jordan has more silt than sand so it is called silty loam and is composed of 2% organic matter. Because it is dry for most of the year, organic material takes longer to decompose, and it takes longer for soil to develop in this area.

9 soil Texture Organic Matter Content (%). 2 4. Fine Sand Very Fine Sand Loamy Sand Loamy Very Fine Sand Sandy Loam Very Fine Sandy Loam Silty Loam Clay Loam Silt Clay Loam Silty Clay Mediterranean Landscape Dynamics Project Universal soil Erosion Equation Worksheet R Factor Very Wet = 90, Moderately Wet = 60, Dry = 30. Jordan was dry during the beginning of the Neolithic, but around 6,000 it changed to a moderately wet cli- mate. These values represent the annual average rainfall. LS Factor When hillsides are steep, water and gravity force the soil down the slope faster. Slope Length (m) Degree of Slope LS- soil Loss Factor 250 200 150 125 2. 110 9 100 90 4. 60 4. 50 45 18 5.

10 C Factor Land that is cleared is more susceptible to soil Erosion than land that is forested. The values for how suscep- tible the land is to Erosion have been determined by scientists. For our area the values are: Forest = .005 (low susceptibility). Cleared Land = (high susceptibility). Mediterranean Landscape Dynamics Project Worksheet Land Type K R LS C P Factor (6) A=. KR(LS)C. (1a) For- ested Flat .42 .005 _____. Mediterranean Landscape Dynamics Project Land (1b) Cleared .42 _____. Flat Land (6) Cleared Flat Land Universal soil Erosion Equation with P. (3a) For- ested Hill- .42 .005 _____. side (3b) Cleared .42 _____. Hillside (6) Cleared Hillside with P. Universal soil Erosion Equation Worksheet For questions 1-7, determine what the rate of soil Erosion will be without factoring in sustainability measures for two different sites in Jordan.