OBJECTIVES. Fluvial Geomorphology? STREAM CLASSIFICATION & RIVER ASSESSMENT

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1 STREAM CLASSIFICATION & RIVER ASSESSMENT Greg Babbit Graduate Research Assistant Dept. Forestry, Wildlife & Fisheries Seneca Creek, Monongahela National Forest, West Virginia OBJECTIVES Introduce basic concepts of river process, form & function Introduce some common geomorphic classification systems Rosgen classification system Discuss methods of morphological assessment Fluvial Geomorphology? Geomorphology - The study of landscapes and their evolution Fluvial Geomorphology The study of erosional and depositional processes from running water that forms the landscape The term "fluvial" was derived from the Latin word "fluvius"" meaning river. Fluvial geomorphology examines the processes that operate in river systems and the landforms which they ultimately create, or have created. - J.R. Miller 1

2 Streams transport water, sediment & energy Geographic Unit = Watershed Physical, Biological, and Chemical Stream channel shape, size, and pattern MAJOR REGIONAL FACTORS AFFECTING RIVER SYSTEM PROCESS, FORM & FUNCTION: Climate (Precipitation) Topography Geology Soils Vegetation Landuse DOMINANT PHYSICAL PROCESSES PHYSICAL PROCESSES HYDROLOGIC PROCESSES HYDRAULIC PROCESSES GEOMORPHIC PROCESSES 2

3 HYDROLOGIC PROCESSES Hydrologic Cycle Precipitation Interception Infiltration Runoff Percolation Evaporation WATER PATHWAYS HYDROGRAPH 3

4 TYPES OF WATER MOVEMENT 8 INTERRELATED HYDRAULIC VARIABLES Bankfull Width Bankfull Depth Velocity Bankfull Discharge Size of sediment Concentration of sediment Water surface slope Roughness of boundary STREAM SCALE (Lane, 1955; FISRWG, 1998) 4

5 STREAM CHANNEL STABILITY Ability of a stream over time, in the present climate, to effectively transport the flows and sediment from its watershed while neither aggrading or degrading and maintaining a stable dimension, pattern and profile. Rosgen (1996) For instance, during droughts there is an increase in change to the river due to climatic change, vegetative influence, high intensity convective thunder storms CONTINUITY EQUATION DISCHARGE (cfs) Q = V x A V = Velocity (ft/s) A = Cross-sectional Area (ft 2 ) V = related to slope, channel shape & boundary roughness CALCULATING DISCHARGE MANNING S EQUATION Q = 1.49 R 2/3 S 1/2 n R = Hydraulic Radius S = Water Surface Slope n = Manning s Roughness Coefficient 5

6 GEOMORPHIC PROCESSES 3 PRIMARY PROCESSES INVOLVED WITH FLOWING WATER: Erosion detachment of soil particles Sediment transport movement of eroded particles in flowing water Sediment deposition settling of eroded particles to the bottom of a waterbody or left behind in the stream bed as substrate or point bar (Schumm,, 1977) RIVER FORM OR MORPHOLOGICAL CONDITION Valley type Drainage Area Dimension (width & depth) Pattern (sinuosity) Profile (bedform( bedform) Channel materials Effective or Bankfull discharge discharge STREAM CORRIDOR CROSS SECTION 6

7 STREAM CORRIDOR LONGITUDINAL PLANFORM CROSS-SECTIONAL SECTIONAL PROFILE PLANFORM 7

8 EFFECTIVE DISCHARGE (Rosgen 1996) Fluvial geomorphologists refer to effective discharge as the stream flow that most efficiently moves sediment through a stream channel BANKFULL DISCHARGE Bankfull stage corresponds to the discharge at which channel maintenance is the most effective, that is, the discharge at which moving sediment, forming or removing bars, forming or changing bends and meanders, and generally doing work that results in the average morphological characteristics of channels. Dunne & Leopold The flow that fills the active channel and begins to spread onto the floodplain BANKFULL FLOW CONTINUED Represents the break between channel processes and floodplain processes Average bankfull discharge recurrence interval 1.5-years Assumed to equal the dominant discharge and effective discharge Bankfull stage is identified from geomorphic features in the field Bankfull discharge is the stream flow that is found to govern channel shape and form Effective discharge of sediment is highly correlated with bankfull discharge 8

9 BANKFULL EVENT East Fork Little Sandy River, E. Kentucky PINE CREEK STREAM CLASSIFICATION 9

10 STREAM CLASSIFICATON SYSTEMS Davis (1899) youthful, mature and old age stage of adjustment Strahler s (1957) Stream order Leopold & Wolman s s (1957) early work on natural alluvial channel patterns Schumm s (1977) Fluvial System Kellerhals et al. (1976) channel pattern, islands, bars, bedform & lateral activity Simon & Hupp (1986) channel evolution model in W. TN Montgomery & Buffington s s (1997) expansion in mountainous regions Rosgen (1994) classification of natural rivers STRAHLER S S STREAM ORDER (Strahler 1957; FISRWG 1998) SCHUMM S S FLUVIAL SYSTEM (Schumm 1977; FISRWG 1998) 10

11 CHANNEL EVOLUTION MODEL (CEM) (Simon 1989; FISRWG 1998) SIMON S S CHANNEL EVOLUTION STAGES (Simon 1989; FISRWG 1998) ROSGEN STREAM CLASSIFICATION Purpose: predict river behavior from morphological description Extrapolate relationships between different stream types Organize and stratify various empirical relations Provide a morphological stratification for companion inventories Provide a consistent frame of reference for communication 11

12 EXAMPLES OF VALLEY TYPE (Rosgen 1996) BROAD LEVEL OF STREAM TYPE DELINEATION (Rosgen 1996) ROSGEN STREAM TYPES (Rosgen 1996) 12

13 CROSS SECTION OF STREAM TYPES (Rosgen 1996) CLASSIFICATION KEY FOR NATURAL RIVERS (Rosgen 1996) FIELD SURVEYS Pedestrian survey Geomorphic surveys Cross sectional surveys Longitudinal profiles Modified Wolman pebble count 100 pebble count in riffle Pattern (Sinuosity) Reference the gage datum 13

14 METHODOLOGY Field assessed bankfull indicators Examine longitudinal profile Examine cross section Regional Curves Perform flood frequency analysis (recurrence interval) TYPICAL CROSS SECTION SURVEY 14

15 TYPICAL CROSS SECTION DIMENSION SURVEY (Rosgen 1996) BANKFULL REGIONAL CURVES A graphical method of illustrating a stream channel s s bankfull hydraulic geometry as a function of basin drainage area within a specific ecoregion and/or hydro-physiographic province Breakdown of regions provides a more accurate depiction of the basin variables affecting stream morphology SOUTHWESTERN APPALACHIANS OF TENNESSEE REGIONAL CURVES Q = (DA).75 Area = 32.48(DA).701 Width = 18.51(DA).444 Depth = 1.76(DA)

16 BANKFULL DISCHARGE VS DA Rock Creek Riffle Cross Section Ground Points Bankfull Indicators Water Surface Points Wbkf = 31.4 Dbkf = 3.2 Abkf = Elevation (ft) Horizontal Distance (ft) EXAMPLE LONG PRO 15 Rock Creek Longitudinal Profile CH WS 10 Elevation (ft) BKF P1 5 P2 P P4 Distance along stream (ft) 16

17 STREAM PATTERN (FISRWG) MEANDER GEOMETRY (Rosgen 1996) 17

18 RIVERMORPH STREAM CHANNEL CLASSIFICATION River Name: CLINCH RIVER Reach Name: Beaver Creek Trib <-- This is not a Reference Reach Drainage Area: 0.43 sq mi State: Tennessee County: Knox Latitude: 0 Longitude: 0 Survey Date: 04/20/05 Classification Data Valley Type: Type VIII Valley Slope: ft/ft Number of Channels: Single Width: 5.91 ft Mean Depth: 1.28 ft Flood-Prone Width: 303 ft Channel Materials D50: 7.18 mm Water Surface Slope: ft/ft Sinuosity: 1.14 Discharge: cfs Velocity: 4.16 fps Cross Sectional Area: 7.59 sq ft Entrenchment Ratio: Width to Depth Ratio: 4.62 Rosgen Stream Classification: STREAM SURVEY RIVER INVENTORY LEVELS (Rosgen 1996) 18

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