. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. FLOWING WATERS. Figure 2. Illinois drainage basins. Riparian Land Cover Streamside riparian buffer strips are an integral part of rivers and streams. They stabilize banks, reduce erosional input, filter agricultural runoff, and protect streams from excessive nutrient loading. Prior to human settlement, the vegetation along Illinois' streams was predominantly forest. With the onset of large-scale agr
. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. FLOWING WATERS. Figure 2. Illinois drainage basins. Riparian Land Cover Streamside riparian buffer strips are an integral part of rivers and streams. They stabilize banks, reduce erosional input, filter agricultural runoff, and protect streams from excessive nutrient loading. Prior to human settlement, the vegetation along Illinois' streams was predominantly forest. With the onset of large-scale agriculture has come a shift in this vegeta- tive cover. Though forested areas and areas of mixed woody and herbaceous vegetation still dominate, the amount of area covered by grasses and cultivated crop fields has increased. Table 1 shows the percentage of cover of various types within 82 ft (25 m) of rivers and streams that drain 10 square miles or more within Illinois. The sources for the land cover (vegetation) information were aerial photographs taken for the Agricultural Stabilization and Conservation Service. After the photographs were interpreted, the findings were entered into the Illinois Streams Information System database. For stream banks within Illinois, eight types of land cover were determined: forested areas (> 45% canopy), areas of mixed vegetation (< 45% canopy), grassy areas (noncultivated), agricultural areas, urban or developed areas, disturbed or barren areas, reser- voirs, and other water areas. For the present report, forested areas and areas of mixed vegetation, grassy areas (noncultivated) and agricultural areas, and reservoirs and other water areas were combined to form a total of five coverage types (Table 1). There are large differences among the 10 drainage basins in the percentages of forest/mixed and agricul- ture/grass buffer strips (Table 1). In the heavily forested southern portion of the state, 81 % of the buffer strip area has forest/mix
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