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Riparian Streams - Berks County: Pennsylvania

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Description:
This is a county wide analysis of Berks County waterways to determine riparian buffer values given a 50 ft., 50% canopy coverage requirement. The analysis was done by first overlaying the stream shapefile on the orthophotos. Next a 50 ft. buffer shapefile was derived from the streamlines and added. Using the newly created buffer shapefile as a guide, visual analysis was done for entire shapefile. The canopy coverage percentage was interpeted by Heritage Conservancy and buffer shapefile was used to define the 50 ft. distance requirement. At a scale of 1:2,000, the streamlines were attributed with one of three riparian values (full, half, none). - Full Value: both banks of the stream contain 50% or greater canopy coverage for 50 ft from the stream. - Half Value: only one bank of the stream contains 50% or greater canopy coverage. - None Value: neither stream bank contains 50% or greater canopy coverage. The threshold for determining whether or not a shoreline segment or a stream centerline segment should be used for the analysis was if the waterway was wider than 100 ft for a linear distance of approximately 400 ft. If a waterway was wider than 100 ft. for a linear distance of approximately 400 ft., shorelines would be used rather than stream centerlines. Having the threshold include a 400 ft linear distance requirement made many ponds be represented by a centerline rather than a shoreline. In cases were the original data contained two shorelines to represent a stream that was not greater than 100 ft wide, a new centerline was created by Heritage Conservancy by using the orthophotos and the shorelines as guides. Ponds that were delineated to represent headwaters were not included in this analysis. Analysis and editing would begin at the tributary originating from the pond, but the pond itself would not be given a riparian value. Edits to the shape of the streamline were done when they were visually obvious. The point of this analysis was not to delineate new stream lines, but rather to give existing streamlines riparian buffer attributes. The large majority of the segments are identical to the original Berks County Planning Commission streamlines. Stream and shorelines were cut into segments based on the riparian attribute value. Ten sites were chosen for on-site verification and they were visited in July 2007. Source Data: Streamlines - The streamlines were obtained from the Berks County Planning Commission in draft form for the analysis. 2004 Orthophotos - The orthophotos were provided by the Berks County Planning Commission. The following is the metadata for the orthophotos: 'An orthoimage is remotely sensed image data in which displacement of features in the image caused by terrain relief and sensor orientation have been mathematically removed. Orthoimagery combines the image characteristics of a photograph with the geometric qualities of a map. For this dataset, the natural color orthoimages were produced at 1-foot pixel resolution. Each orthoimage provides imagery for a 10,000 by 10,000 feet block on the ground. The projected coordinate system is Pennsylvania State Plane with a NAD83 datum. There is no image overlap been adjacent files. The ortho image filenames were derived from the northwest corner of each ortho tile using the first four digits of the northing and easting coordinates referenced to the Pennsylvania State Plane coordinate system, followed by the State designator 'PA', and the State Plane zone designator 'S'. This dataset consists of 10000' x 10000' uncompressed natural color (24-bit) GeoTIFF files with ESRI world files and MrSid compression format at a pixel resolution of 1'. Digital orthophotography combines the image characteristics of a photograph with the geometric qualities of a map. Digital orthophotography is a process which converts aerial photography from an original photo negative to a digital product that has been positionally corrected for camera lens distortion, vertical displacement and variations in aircraft altitude and orientation. The imagery was captured at a negative scale of 1:19200 for the purpose of producing orthophotos.'
Collection:
Pennsylvania Spatial Data Access (PASDA)
Place:
Pennsylvania, United States
Subjects:
Hydrology and Inland Waters
Year:
2007
Contributed by:
Penn State
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