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RIVER SYSTEMS AND LANDFORMS (1)
RIVER DRAINAGE BASINS
AND RIVER BEHAVIOUR
1. Introduction
2. Rivers and drainage basins
3. River discharge
4. The river basin system
5. Hydrographs and floods
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Am
azon
Con
go
Yan
gtze
Orin
oco
La Pla
ta-P
aran
a
Gan
ges-
Bra
hmap
utra
Yen
isey
Mississ
ippi
Lena
St. Law
renc
eN
ile
Riv
er d
isch
arge
(m3/s
)
World’s largest rivers by discharge. Source: Christopherson, 2012, p. 401.
Human impacts on the global water system.
Source: Vörösmarty et al., 2004, Humans transforming the global water system, Eos 85, 48.
WHAT IS A RIVER?
A river is a body of water
flowing downslope in a
physically distinct channel.
Formation of river channels from sheetflow, rills
and gulleys. See also Christopherson, 2012, p. 402.
Development of rills in a slope above McIntyres
Bluffs, shore of Lake Ontario. Source: SUNY Oswego Geology Dept., photo by Sharon Gabel.
Rills in a farm field.
Rills in Capitol Reef
National Park.
Gulleys and rills can eventually erode topsoil
significantly; river channels may eventually form.
Source: Geography Dept., Union College, Schenectady NY.
Drainage basins, rills and gulleys. Source: Christopherson, 2012, p.402.
Source: US Army Corps of Engineers.
Drainage basins scale.
Source: Christopherson, 2012, p.402.
Drainage basins and continental divides.
Source: Christopherson, 2012, p. 403.
Closed basins:
internal drainage
and exotic streams.
Source: Salt Lake Tribune.
The Colorado River
drainage basin.
Source: Dettinger, 1995.
The Colorado River
drainage basin.
Source: Christopherson, 2012, p. 449.
The Colorado River
delta, September 8 2000.
Source: NASA’s Visible Earth.
DRAINAGE DENSITY
Total length of stream channels (km)
Total area drained by channels (km2)
High drainage density
Low drainage density
DRAINAGE DENSITY
Total length of stream channels (km)
Total area drained by channels (km2)
Depends on:
• erodibility of surface
• erosiveness of flow
Very high drainage density in Badlands
National Park, South Dakota.
Source: photo by Drew Milsom, Physics Department, University of Arizona.
Drainage patterns. Source: Christopherson, 2012, p.406.
Dendritic Trellis Radial Parallel
Drainage patterns. Source: Christopherson, 2012, p.406.
Dendritic Trellis Radial Parallel
An example
of radial
drainage:
Mt. Rainier,
Washington.
Source: Mt. Rainier
National Park.
Radial drainage
on Mt. Rainier,
WA. Source: GoogleEarth
An example of trellis drainage:
the Shenandoah River basin.
Source: Virginia Department of Game and Inland Fisheries.
An example of trellis drainage: the Shenandoah
River basin. Source: Virginia Department of Game and Inland Fisheries.
RIVER DISCHARGE
Q = w d v
Discharge Width depth
velocity
Also expressed as Q = a v
Cross-sectional area
(width times depth) Zone of fastest flow
Measuring discharge in a straight section of river.
Channel shape
affects river
velocity: 1941
flood of the
San Juan
River near
Bluff, UT.
Source: Christopherson,
2012, p. 408.
Channel shape
affects river
velocity: 1941
flood of the
San Juan
River near
Bluff, UT.
Source: Christopherson,
2012, p. 408.
THE RIVER BASIN SYSTEM
Overland flow
(surface runoff) Soil
Bedrock
Groundwater flow
Through flow
Precipitation
Interception
Capitol Reef National Park, 2009.
Dry waterfall in
Capitol Reef National
Park, 2009.
The same waterfall 24
hours earlier.
Str
eam
dis
char
ge
and p
reci
pit
atio
n
Time Precipitation event
Hydrographs showing the effects of urbanization. Source: Christopherson, 2012, p. 428.