Acknowledgements

1. 2004 Channel Migration Zone (CMZ) STUDY for theDuckabush, Dosewallips, Big Quilcene and Little Quilcene Rivers South Jefferson County by Jeanne E. Klawon

2. Acknowledgements • Patricia Olson & Jeff Stewart, State of Washington Department of Ecology • Dave Christensen & Josh Peters, Jefferson County Natural Resource Division • Dave Nelson, Bureau of Reclamation Pacific Northwest Region • Ted Labbe, Port Gamble S’klallam Tribe Natural Resources Department • Sue Perkins, Perkins Geosciences • Dan Levish, Bureau of Reclamation Technical Services Center

3. Why delineate CMZs? • To reduce risks to human development and infrastructure • To reduce risks to riparian habitat by protecting it from development Courtesy of Department of Ecology

4. Components of CMZ’s • The Historical Migration Zone (HMZ) • The collective area the channel occupied in the historical record • The Avulsion Hazard Zone (AHZ) • Avulsion: abrupt change in the course of a stream, whereby the stream abandons its old channel for a new one • The area not included in the HMZ that is at risk of avulsion over the timeline of the CMZ Courtesy of Department of Ecology; Rapp and Abbe (2003)

5. Middle Fork Nooksack River Courtesy of Department of Ecology

6. Components of CMZ’s (continued) • The Erosion Hazard Area (EHA) • The area not included in the HMZ or AHZ that is at risk of bank erosion from stream flow or landsliding over the timeline of the CMZ • The Erosion Setback (ES) • Area at risk of future bank erosion • The Geotechnical Setback (GS) • Banks that are at risk of mass wasting • The Disconnected Migration Area (DMA) • Portion of the CMZ where man-made structures physically eliminate channel migration Courtesy of Department of Ecology; Rapp and Abbe (2003)

7. Banks prone to landsliding (i.e., mass wasting) are part of CMZs Lower Elwha River Courtesy of Department of Ecology

8. The Final CMZ Delineation is the Cumulative Result of Historical Analysis and Field Observations: CMZ = HMZ + AHZ + EHA - DMA HMZ = Historical Migration Zone AHZ = Avulsion Hazard Zone EHA = Erosion Hazard Area (= ES + GS) ES = Erosion Setback from edge of HMZ or AHZ GS = Geotechnical Setback from edge of ES DMA = Disconnected Migration Area Courtesy of Department of Ecology

9. Courtesy of Department of Ecology

11. The Historical Migration Zone (HMZ)

13. The Avulsion Hazard Zone (AHZ) • Methods • Soils • Aerial photos and Lidar (surface morphology) • Height measurements above active channel • Vegetation • Description • Channelized surface • Young vegetation (alders) • Sandy and silty soils over gravelly substrate • Intermediate height above active channel

15. The Erosion Hazard Area (EHA) • EHA= ES + GS • ES = Erosion setback • GS = Geotechnical setback • Erosion Setback (ES) methods • Channel Migration measurements • Channel width measurements • Meander Amplitude measurements • Geotechnical Setback (GS) methods • Assumed 1:1 slope for setback along high bluffs prone to lateral erosion and slumping

19. Rivers studied during the 2004 CMZ Study: Little Quilcene River Big Quilcene River Dosewallips River Duckabush River

25. Channel migration measurement

40. CMZ Study Summary • HMZ: encompasses lateral extent of historical channels from ~1880 to 2000/2002 • AHZ: occupies low to intermediate height terraces with subdued channels that are prone to future channel avulsion; most extensive in deltaic areas • EHA: combines erosion setback (ES) and geotechnical setback (GS) • ES: defines width of area prone to lateral erosion; located on higher terraces with planar surfaces and mature vegetation (including large cedar stumps); width of ES determined by magnitude of historical channel changes and character of channel geometries from 1939 to 2000/2002 • GS: defined by 1:1 slope of high bluffs prone to lateral erosion or slumping

41. Defining the hazards • Channel migration zones (CMZ’s) • Levees and revetments • Other factors