. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. a 1 & E. Figure 3. Percentage of each basin's total stream length that has been altered through channelization. Data were collected from 1981 to 1990 and cover only those streams that drain an area of 10 sq. mi. of the basin or more and; therefore, the data most likely underestimate the basin-wide percentage of channelized streams. Channelization data were collected from several sources: (1) an
. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. a 1 & E. Figure 3. Percentage of each basin's total stream length that has been altered through channelization. Data were collected from 1981 to 1990 and cover only those streams that drain an area of 10 sq. mi. of the basin or more and; therefore, the data most likely underestimate the basin-wide percentage of channelized streams. Channelization data were collected from several sources: (1) an Illinois Depart- ment of Conservation (IDOC) Division of Fisheries report titled "Channelized Streams and Ditches of Illinois," (2) county highway maps from the Illinois Department of Transportation (1D0T), (3) Agricultural Stabilization and Conservation Service (ASCS) aerial photogrtaphy slides, and (4) the most recent Geological Survey (USGS) topographic maps. The IDOC report listed the lengths of channelized stream segments per county but did not give the location. Channelized stream segments were located using county highway maps, ASCS aerial slides, and USGS topographic maps. Ground truth surveys in the Sangamon River basin were then carried out to verify the location accuracy of several of these stream segments. Figure 4. Percentage of stream length that is bordered by public land in each basin. To assess the extent of accessible public land holdings along Illinois' streams, the most recent county plat books and government agency publications about land holdings were used to identify owners, who were then contacted for more specific information about these sites. The Sangamon Basin was the first completed by the Illinois Streams Information System (ISIS). It was the testing ground for surveys used in the other basins. Included in the Sangamon Basin are areas such as privately owned golf courses, scouting camps, country clubs, utilities
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