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Service Description: The TWI is a physically based index or indicator of the effect of local topography on runoff flow direction and accumulation. The index is a function of both the slope and the upstream contributing area. The computation of TWI is performed using both geographic information systems (GIS) and Python, a programing software used to enhance computing capabilities. The indices help identify rainfall runoff patterns, areas of potential increased soil moisture, and ponding areas. Illinois State Water Survey generated the index to the Illinois counties of DuPage and Will (see report at http://hdl.handle.net/2142/98495), but has subsequently generated the index for most Illinois counties as high resolution DEMs derived from LiDAR have become available. The DEM used for this county was derived from LiDAR acquired between 2009 and 2018. While TWI is usually viewed in raster format, ISWS is distributing a version in polygon format for easier access and use.
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Spatial Reference:
102100
(3857)
Single Fused Map Cache: false
Initial Extent:
XMin: -1.0099729650497967E7
YMin: 4940841.429688792
XMax: -1.0099644983661966E7
YMax: 4940875.428715123
Spatial Reference: 102100
(3857)
Full Extent:
XMin: -1.018718415625043E7
YMin: 4434922.564837374
XMax: -9739923.2263
YMax: 5237435.286499999
Spatial Reference: 102100
(3857)
Units: esriMeters
Supported Image Format Types: PNG32,PNG24,PNG,JPG,DIB,TIFF,EMF,PS,PDF,GIF,SVG,SVGZ,BMP
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Comments: The TWI is a physically based index or indicator of the effect of local topography on runoff flow direction and accumulation. The index is a function of both the slope and the upstream contributing area. The computation of TWI is performed using both geographic information systems (GIS) and Python, a programing software used to enhance computing capabilities. The indices help identify rainfall runoff patterns, areas of potential increased soil moisture, and ponding areas. Illinois State Water Survey generated the index to the Illinois counties of DuPage and Will (see report at http://hdl.handle.net/2142/98495), but has subsequently generated the index for most Illinois counties as high resolution DEMs derived from LiDAR have become available. The DEM used for this county was derived from LiDAR acquired between 2009 and 2018. While TWI is usually viewed in raster format, ISWS is distributing a version in polygon format for easier access and use.
Subject: The topographic wetness index shows areas with increased accumulated runoff potential, and areas with low slope and large upslope contributing areas.
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Keywords: TWI
AntialiasingMode: None
TextAntialiasingMode: Force
Supports Dynamic Layers: true
MaxRecordCount: 1000
MaxImageHeight: 4096
MaxImageWidth: 4096
Supported Query Formats: JSON, geoJSON
Supports Query Data Elements:
Min Scale: 1000000
Max Scale: 500
Supports Datum Transformation: true
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