Metadata for Channel Migration Zone of Lower Prickly Pear and Lower Tenmile Creeks, Montana, 2011 Metadata for Channel Migration Zone of Lower Prickly Pear and Lower Tenmile Creeks, Montana, 2011

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Identification Information:

Citation:

Originator: Applied Geomorphology
Originator: DTM Consulting, Inc.
Publication date: 01/14/2011
Title:: Channel Migration Zone of Lower Prickly Pear and Lower Tenmile Creeks, Montana, 2011
Online linkage: https://msl.mt.gov/geoinfo/data/montana_channel_migration_zones/projects/prickly_pear_and_lower_tenmile_creeks

Abstract:

This dataset was created to support Channel Migration Zone development for Prickly Pear and Tenmile Creeks in the Helena Valley of Montana.

The Prickly Pear/Tenmile Creeks CMZ is defined as the combined area that includes:
- Historic Migration Zone (HMZ): the area of historic channel occupation, usually defined by the available photographic record.
- Erosion Hazard Area (EHA): the area outside the HMZ susceptible to channel occupation due to channel migration or mass wasting.
- Avulsion Hazard Zone (AHZ): floodplain areas geomorphically susceptible to abrupt channel relocation.
- Restricted Migration Area (RMA): areas of CMZ isolated from the current river channel by constructed bank and floodplain protection features (also known as the Disconnected Migration Area, or DMA).

The historic and modern positions of Prickly Pear and Tenmile Creeks were determined through a GIS-based analysis of aerial photography. The resulting mosaic of historic channel locations forms the foundation for the CMZ delineation. Within the GIS, the digitized banklines were evaluated in terms of discernible channel shift since 1955. Where migration was identifiable, vectors were drawn in the GIS to record that change. At each site of bankline migration, three measurements were collected, and the vectors were attributed with reach, eroding site identification, and line length. These measurements were then summarized by site and by reach to determine appropriate reach-specific buffer widths to accommodate future shifts in channel location.

The reach-specific buffer was then applied to the 2008 banklines to define the Erosion Hazard Area. Potential avulsion pathways outside the HMZ and EHA were then added to the composite CMZ.

Purpose:

Complete Channel Migration Zone (CMZ) layer, including the 2008 channel, HMZ, erosion buffer and AHZ. This dataset was created to support Channel Migration Zone development for Prickly Pear and Tenmile Creeks in the Helena Valley of Montana..

Time period of content:

Calendar date: 01/14/2011
Currentness reference: publication date

Status:

Progress: Complete

Access constraints: None

Use constraints:

This dataset should be used in conjunction with the final Channel Migration Zone report dated January 14, 2011, also available from the Lewis and Clark County Office of Community Development and Planning.

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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