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Land Assessment

 

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Chapter 5 - Results & Analysis

1999 Land Use & Land Cover Accuracy Assessment  |  1984 & 1999 Land Use & Land Cover Statistics  |  Quantitative Change Detection & Analysis  |  Land Assessment

Land Assessment

An assessment of the suitability or potential sustainability of the land on which land use and land cover change has taken place is an important consideration. The conversion of forests to pasture can potentially have adverse affects upon the landscape. Important components such as natural vegetative cover, slope, and the properties of soil help to maintain the balance of the landscape. These variables can be negatively impacted as a result of land use change. The land suitability assessment was determined by cross-tabulation of three parameters: slope, erodibility, and land productivity. The analysis of these three parameters in terms of the total amount of cleared forest in Carroll County is presented in the following three tables. (Tables 5.9, 5.10, 5.11) Table 5.9 compares slope and erodibility classifications for areas of cleared forest.

Table 5.9  Slope & Erodibility Classifications for Areas of Cleared Forest in Carroll County, Arkansas 1984 – 1999

Slope Categories

Nearly Level to Gently Sloping: 0 – 6 Degrees

Moderately to Steeply Sloping: 7 – 14 Degrees

Excessive Slope: > 14 Degrees

Table 5.10  Slope & Prime Farmland Classifications for Areas of Cleared Forest in Carroll County, Arkansas 1984 - 1999

Slope Categories

Nearly Level to Gently Sloping: 0 – 6 Degrees

Moderately to Steeply Sloping: 7 – 14 Degrees

Excessive Slope: > 14 Degrees

Table 5.11  Prime Farmland & Erodibility Classifications for Areas of Cleared Forest in Carroll County, Arkansas 1984 - 1999

Table 5.10 compares slope and prime farmland classifications for areas of cleared forest and Table 5.11 compares prime farmland and erodibility classifications for areas of cleared forest. It should be noted that the total amount of area considered in each of these comparisons (cross-tabulations) is not consistent. This is a result of the county boundaries between Carroll County and Benton County, to the west, having changed twice within the period of study and all the data utilized in this land assessment has not been updated to reflect this change. Specifically, the erodibility and the prime farmland.

classifications obtained from the SSURGO data do not reflect this boundary change. However, this difference in area is minimal, to within three one-hundredths of a square mile, and not considered to be significant with respect to the total area of cleared forest. Essentially, 0.03 of a square mile, 8.67 acres, of the 12.43 square miles is not analyzed in the land assessment.

Additionally, each data layer comprised in the land assessment has been mapped separately on the basis of the areas of cleared forest in Carroll County. These maps allow for further visual analysis of each of these three important variables incorporated in the land assessment: slope, erodibility, and land productivity. Map Foldout 5.5 portrays the slope classifications of the areas of cleared forest, Map Foldout 5.6 portrays the erodibility classifications of the areas of cleared forest, and Map Foldout 5.7 portrays the prime farmland classifications of the areas of cleared forest in Carroll County.

By analyzing the previous three tables (Tables 5.8, 5.9, & 5.10), an important statistic of note is the erodibility of the areas of cleared forest. Approximately 85 percent (85.4%) of the cleared forest area is classified as highly erodible, 10.61 square miles. In addition, when factoring the slope of these areas, 5.13 square miles of forest, 48.35% of the highly erodible land or 41.27% of the total cleared forest, was cleared on moderately to steeply sloping hillsides of 7 to 14 degrees. Furthermore, 0.70 of a square mile of forest, (447.59 acres) or 6.60% of the highly erodible land or 5.63% of the total cleared forest, was cleared on hillsides with an excessive slope greater than 14 degrees. The remaining 4.78 square miles of forest, 45.05% of the highly erodible land or 38.46% of the total cleared forest, was cleared on nearly level to gently sloping hillsides of 0 to 6 degrees.

Map Foldout 5.5

Map Foldout 5.6

Map Foldout 5.7

To complete the erodibility assessment, 14.6% of the cleared forests in Carroll County, 1.57 square miles (12.63%) of the cleared forest was classified as being potentially highly erodible and only 0.23 square miles, 145.64 acres or 1.85%, was classified as being not highly erodible.

It comes as no surprise that 99.03% or 12.31 square miles of the cleared forest and resulting new pasture in Carroll County was not classified as prime farmland. Throughout much of Carroll County and northwest Arkansas, most pasture is utilized for cattle grazing and hay production. It should be noted that the definition of prime farmland includes hay as a cultivated field crop. In addition, all the land classified as highly erodible, was also classified as not prime farmland, 10.61 square miles or 85.4% of the total cleared forest. Of the remaining 1.71 square miles of not prime farmland, 1.55 square miles was classified as potentially highly erodible and only 0.16 square miles (102.28 acres) was classified as not highly erodible. Only 0.09 square miles (58.03 acres), or 0.72% of the total area of cleared forest in Carroll County was classified as prime farmland.

Based upon this assessment, the clearing of forested areas on highly erodible soils and on slopes that range from moderate to excessive for the conversion to pastures, on land which has been classified as not prime farmland by the USDA, National Soil Survey Center, is occurring in Carroll County, Arkansas.