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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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.