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Table 7.2 Historical aerial photography
Wetland name
County
Years collected
Green acres
Clay
1938, 1968, 1993
Moses hill
Phelps
1938, 1968, 1993
Straight water
Seward
1938, 1965, 1993
of two other types of imagery: IKONOS satellite imagery and historical aerial
photography, respectively.
IKONOS, a commercial satellite operated by GeoEye, provides imagery having
high spatial resolution (approximately 1 m), comparable to much aerial photog-
raphy ( http://www.geoeye.com ). IKONOS imagery was available for 49 of the
87 targeted RWB wetland basins. Pan-sharpened images that combine the spatial
detail of the IKONOS panchromatic channel with the spectral information of the
4 m multi-spectral sensor were obtained, mosaicked where required, clipped to the
basin boundaries and converted to GeoTIFF format. The GeoTIFF files were then
compressed using MrSID software using a 3:1 compression ratio.
Aerial photography has been collected over most of the U.S since about the mid-
1930s. Historical photos provide valuable archival records of land use, land cover
and land management. However, most are available only in paper format. In this
project, for demonstration purposes, three dates of historical aerial photography
were obtained for three wetland basins within the RWB study area (Table 7.2 ).
Paper prints of the photography were acquired from the Conservation and Survey
Division archives at the University of Nebraska-Lincoln. The black and white
photographs were scanned at 500 dpi, rectified using Digital Orthophoto Quarter
Quadrangles, mosaicked and clipped to the wetland basin boundaries.
7.4 Modeling Potential Soil Erosion
Assemblage of a suite of key geospatial datasets, including demonstration of the
value of remote sensing, were important achievements for the RWBJV. The partners
recognized that these datasets can serve many needs in wetlands management, but a
special interest was expressed in developing GIS-based models to aid in supporting
management decisions and planning. In the RWB region, a particular concern is
soil erosion because of the potential impacts of siltation on remaining wetlands.
RWBJV staff need to be able to identify areas where soil erosion threatens wetlands,
and prioritize time and funds to target the most endangered basins for rehabilitation
and/or protection.
The Universal Soil Loss Equation (USLE), developed by Wischmeier and Smith
( 1965 ), has been widely used to estimate potential soil erosion. In this project, an
updated implementation of the USLE, the Revised Universal Soil Loss Equation
(RUSLE) was used to assess soil erosion for both individual wetland basins and for
 
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