GEOGRAPHIC INFORMATION

Channel Migration Zone of the Big Hole River, 2005

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Data Provider DTM Consulting, Inc.
Applied Geomorphology, Inc.
Date 2005
Content Type Downloadable Data
Abstract The Big Hole River Channel Migration Zone (CMZ) is a delineation of past, current, and anticipated zones of active bank erosion and channel movement. The Big Hole River CMZ is defined as the combined area that includes:- the active channel location approximately 50-60 years ago;- the 1995 channel location; and,- a buffer width applied to the 1995 channel boundaries based on measured historic migration rates.The result is a composite zone of historic channel locations, with variable buffer widths on the 1995 channel margins that reflect the relative lateral migration rates of individual river reaches.The historic and modern (1995) positions of the Big Hole River were determined through a GIS-based analysis of aerial photography. The primary historic photo set utilized in the historic channel assessment was from 1955. These photos were supplemented by 1942 and 1951 photos to fill a few gaps in coverage. All of the historic photographs were scanned and rectified into the project GIS. The modern channel was mapped using 1995 Digital Orthophoto Quads (DOQs), which are readily available for the entire project area.Channel banklines were digitized to record the normal high water channel boundaries. The 1942, 1955, and 1995 photos were digitized at a scale of 1:3,000; the 1951 photos were of lower quality, and were digitized at 1:5,000. The normal high water mark was typically identified by the transition from open bar area or water to woody riparian vegetation. Where woody riparian vegetation is not present in the river corridor, the boundaries were defined using supplemental indicators such as water lines, depositional bars and contrast changes in herbaceous vegetation.The following features were digitized as active channels:- Continuous primary channels that convey the majority of flow during low flow conditions;- Continuous side channels that constitute at least 1/3 of the main channel width;- Active chute channels that reflect active meander cutoff through a secondary channel across a meander core; and,- Oxbows (relict meander cutoffs) that maintain low flow continuity with the main channel.The resulting mosaic of historic channel locations forms the foundation for the CMZ delineation. Additionally, relic channels were digitized to help identify floodplain swales, abandoned channels, and flood conveyance channels.
Purpose Define the composite Channel Migration Zone for the Big Hole River.
Supplemental Information
The corridor delineations presented in this geodatabase are intended to provide a basic screening tool to help guide and support management decisions. The expanse of the project area requires that the results are broad-scale in nature, and therefore less precise than highly detailed site-specific analyses. The results are unequivocally not intended to replace or override site-specific assessments; conversely, they are intended to highlight areas that would warrant such assessments as necessary. The Montana State Library provides this product/service for informational purposes only. The Library did not produce it for, nor is it suitable for legal, engineering, or surveying purposes. Consumers of this information should review or consult the primary data and information sources to ascertain the viability of the information for their purposes. The Library provides these data in good faith but does not represent or warrant its accuracy, adequacy, or completeness. In no event shall the Library be liable for any incorrect results or analysis; any direct, indirect, special, or consequential damages to any party; or any lost profits arising out of or in connection with the use or the inability to use the data or the services provided. The Library makes these data and services available as a convenience to the public, and for no other purpose. The Library reserves the right to change or revise published data and/or services at any time.
Data Access https://msl.mt.gov/geoinfo/data/montana_channel_migration_zones/projects/big_hole_river
Distributor Montana State Library
PO Box 201800
 Helena, MT 59620-1800
Telephone: 406-444-5354
TDD/TTY: Montana Relay 711
Fax: 406-444-0266
Email: geoinfo@mt.gov
Distribution liability The Montana State Library provides this product/service for informational purposes only. The Library did not produce it for, nor is it suitable for legal, engineering, or surveying purposes. Consumers of this information should review or consult the primary data and information sources to ascertain the viability of the information for their purposes. The Library provides these data in good faith but does not represent or warrant its accuracy, adequacy, or completeness. In no event shall the Library be liable for any incorrect results or analysis; any direct, indirect, special, or consequential damages to any party; or any lost profits arising out of or in connection with the use or the inability to use the data or the services provided. The Library makes these data and services available as a convenience to the public, and for no other purpose. The Library reserves the right to change or revise published data and/or services at any time.
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Metadata date 11/18/2014

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