1. Meandering Stream

2. Floodplain Definitions Topographic: first flat surface found along the river above the bankfull channel; Geomorphic: landform composed of unconsolidated sediments transported and deposited by the related stream (created by the river and composed of alluvial materials); Hydrologic: surface subject to periodic flooding by the stream and exerts a role in the hydrologic characteristics of the drainage basin (example – 100- year floodplain).

3. Topographic Features Levees: Ridge that runs parallel to the river; due to enhanced deposition of sediment along the channel margins and a decrease in sediment size away from the channel; Splays: fan-shaped deposits associated with a breach in a levee; Splays are generally composed of coarser sediments than the levees; Oxbows and oxbow lakes: created by meander cutoffs; Slowly fill in with sediment; commonly fine- grained (clay plugs), but not always.

4. From reineck and Singh, 1980

6. 1:12,000 Overbank Flood Deposits (1997) Deposits are Contaminated with Hg

7. Overbank Flood Deposits

8. Primary Processes Involved In Floodplain Formation Lateral Migration: lateral movement of the channel across the floodplain; consists of erosion of outer bank and deposition on the point bar. Produces fining upward deposits of semi-uniform thickness.

9. Lateral Accretion of Floodplain Deposits by a Meandering Channel

10. Primary Processes Involved In Floodplain Formation Lateral Migration: lateral movement of the channel across the floodplain; consists of erosion of outer bank and deposition on the point bar. Produces fining upward deposits of semi-uniform thickness. Vertical Accretion: deposition of sediment over the top of the floodplain during flood events; Produces horizontally bedded layers with varying degrees of lateral continuity.

11. Vertical Accretion

12. Common Stratigraphic Facies Lateral accretion deposits: produced by lateral accretion. Vertical accretion deposits: produced by vertical accretion. Channel Fill Deposits: sediments deposited during aggradation of an active channel or a paleochannel (e.g., an oxbow); variety of types. Channel lag deposits: found at base of the channel; formed by extensive reworking of the materials (and winnowing of the fines) during floods; associated with the thalweg; Colluvium: material shed from the surrounding hillslopes under the influence of gravity with may be interbedded with alluvial sediments; commonly more angular and coarser grained than floodplain materials.

13. From reineck and Singh, 1980

15. From Leeder, 1982

16. Qa3

18. From Miller et al., 1998

20. From Macklin, 1996

22. 1:12,000 Overbank Flood Deposits (1997) Deposits are Contaminated with Hg

23. From Miller et al., 1999

24. Reservoir 0 1 1B 2 2B 3 4 5 6 7 7B 7C 7D 910 11 12 13 14 15 16 17 18 Gaging station Gaging Station Mineral Canyon Dayton Carson City Virginia City Table Mtn. Canyon (Brunswick) Fort Churchill 395 0 01234 12345 Miles Km 95 Six Mile Canyon Fan Gold Canyon S i x M i l e C a n y o n F o r k Carson City Carson River Watershed Boundary Carson Lake Carson Playa Stillwater Wildlife Refuge Lahontan Reservoir Lake Pyramid SIERRA NEVADA Nevada California F o r k E a s t T r u c k e e R. C a r s o n R. T r u c k e e R. W e s t F o r k C a r s o n R.. Lake Tahoe Lahontan