Views of a River

1
Views of a River
Cross-Sectional View (Dimension)
Plan View (Pattern)
Longitudinal View (Profile)
2
Cross-Sectional View
3
Bankfull ElevationandBankfull Discharge

• In stable channels, bankfull identifies
  breakpoint where active channel ends and
  floodplain begins.
• Bankfull has been equated to dominant discharge
  and effective discharge (Knighton, 1998 Leopold
  1994).
• The return interval is about 1.5 years or 67
  chance per year (Leopold et al., 1964)

4
Bankfull Indicators

• Only bankfull can be identified in the field.
• May be quite difficult to identify, but very
  important
• May or may not be top of bank, depending on
  whether or not the channel is incised.

5
Bankfull Indicators

• Indicators include
• Top of bank where flood plain begins
• Back of point bar
• Upper break of bank slope
• Change in vegetation
• Bench
• Change in particle size distribution (coarse to
  fine)
• Upper scour line (Secondary)
• Staining of rocks (Secondary)
• Verify with multiple indicators downstream

6
Bankfull Indicators
7
Bankfull Indicators
8
Cross-Sectional View

• Dimension
• Bankfull Width
• Flood Prone Width
• Bankfull Depth
• W/D Ratio
• Cross-sectional Area
• Entrenchment

9
Cross-Sectional View

• Width/Depth Ratio
• Dimension and shape of
• Bankfull channel

10
Entrenchment Ratio Flow Width _at_ 2X Bank-Full
StageBank-Full Width
11
Cross-Sectional View

• Entrenchment Ratio
• Relationship of river to valley
• Entrenched (1.0 1.4)
• Moderately Entrenched (1.41 2.2)
• Slightly Entrenched (gt 2.2)

12
Regional Curves
13
? MeanderWavelength
Radius of Curvature
Belt Width
P Sinuosity River Distance (Measured along
Thalweg) / Straight-Line Distance
14
Sinuosity (P)

• 1.0 - 1.2 Low
• 1.2 - 1.5 Moderate
• 1.5 High

Measured Along Thalweg
15
Meandering Stream, Sinuosity gt3
http//www.geosurv.gov.nf.ca/education/features/ge
omorph.html
Photo Geolgical Survey of Newfoundland Labrador
Ox-Bow Lakes
Abandoned Meanders
16
Longitudinal View

• Profile
• Water Surface Slope

A
A
B
B
17
Rosgen Classification System

• Who uses it?
• EPA
• States
• USDA (NRCS)
• USACOE
• Why do they use it?
• Quantifiable
• Becoming widespread
• Usable by various disciplines
• Allows prediction of rivers behavior from
  appearance
• Packaged for engineering applications

18
Rosgen Stream Classification Criteria

• Single Channel vs. Multiple Channels
• Entrenchment Ratio
• Width/Depth Ratio
• Sinuosity
• Slope
• Bedload Texture

19
Rosgen Stream Classification, Fig
5-3http//www.r6.fws.gov/pfw/images/Class2.gif
20
Stream types gradient, cross-section, plan view
(from Applied River Morphology, Dave Rosgen and
Hilton Lee Silvey, Wildland Hydrology, Pagosa
Springs, Colorado, 1996.)
21
Stream Types

• A Type Stream
• High gradient
• Entrenched
• Low Sinuousity
• Step Pools Common
• Colluvial Deposition
• Large Sediments Dominate Bed

22
Stream Types

• B Type Stream
• Moderate gradient
• Moderately entrenched
• Riffle/rapid dominated
• Infrequently spaced pools
• Colluvial deposition/ residual soils

23
Stream Types

• C Type Stream
• Low gradient
• Slightly entrenched
• Meandering
• Point bar
• Well developed floodplains
• Riffle Pool
• Alluvial soils

24
Stream Types

• E Type Stream
• Low gradient
• Slightly entrenched
• Well developed floodplain
• Meandering- highly sinuous
• Riffle pool
• Low W/D
• Efficient and stable
• Alluvial soils

25
(No Transcript)