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This layer represents the Channel Migration Zone along the Sandy River based on analysis designed by Rapp and Abbe, 2003. The Channel Migration Zone (CMZ)... |
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This layer represents the Channel Migration Zone along the Sandy River based on analysis designed by Rapp and Abbe, 2003. The Channel Migration Zone (CMZ)... |
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John T. English, Daniel E. Coe, and Robert D. Chappell |
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5000 |
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[] |
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<DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>Conventional flood hazard maps, like the FEMA Flood Insurance Rate Map (FIRM) series, examine only the hazard posed by standing floodwaters on a given floodplain. Damage from bank erosion as river channels naturally migrate may be far greater locally and may occur even in the absence of major flooding. To address this hazard, channel migration hazard maps were created to identify areas susceptible to future channel movement and erosion. Following the methodology of Rapp and Abbe (2003) and Abbe and others (2008), lidar-derived digital elevations models and serial aerial photography were examined to map the position of the channel over time. Localized erosion rates, potential avulsion sites, areas where erosion may be prevented, and areas where infrastructure is at risk from erosion were identified from these data. The resulting Channel Migration Zone and its subzones represent best estimates of the likely hazard projected 100 years into the future. The analysis area is mostly within the geologic floodplain of the river, with some exceptions where forecasted erosion boundaries intersect active landslides. In these locations, the Channel Migration Zone may include the landslide toe. The channel hazard maps should be used as a guide for local governments, land owners, and infrastructure managers to identify assets potentially at risk and to develop effective mitigation measures. For more information on methodologies, see DOGAMI OFR O-11-09, Channel Migration Hazard Maps, Coos County, Oregon.</SPAN></P><P><SPAN /></P></DIV></DIV></DIV> |
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<DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>This data depicts channel migration zones and associated hazards based on interpretation of serial aerial photography and lidar elevation data. Migration paths/zones and hazard areas were created using methods and protocols defined by Rapp and Abbe (2003). This data cannot serve as a substitute for site-specific investigations by qualified practitioners. Site-specific data may yield results that differ from those shown on this map. This product is for informational purposes and may not have been prepared for or be suitable for legal, engineering, or survey purposes. Users of this information should review or consult the primary data and information sources to ascertain the usability of the informationn.</SPAN></P><P><SPAN>This map is created from a subset of data from a Geographic Information System (GIS) database. Multnomah County makes no claims, representations, or warranties, express or implied, concerning the validity, reliability or accuracy of the GIS data and GIS data products furnished here, and each user of this data is responsible for determining its suitability for their intended purpose.</SPAN></P></DIV></DIV></DIV> |
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Lower Sandy River Channel Migration Zone (CMZ) |
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["United States","Oregon","Multnomah County","Department of Community Services","Land Use","CMZ","inlandWaters","Sandy River","Oregon","channel migration zone","geoscientificInformation"] |
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en-US |
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500000 |
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