River landscapes

Why are rivers important?

• Supply and agriculture

• Biodiversity and ecossytems

• transportation and tourism

• Cultural heritage

River emerge

the interaction of flowing water and a boundary (soil, rock, or ice) that can evolve in response to flow.

River main jobs

Moving water and Moving sediment

River move water 

River move sediments

How are rivers organized?

Into networks to funnel water through the landscape.

Drainage basin (or catchment, or watershed)

All of the area that contributes water to a downstream point.
Synthesizes the effects of local topography and geology. 

Drainage density 

reflects the efficiency with which water moves through a landscape. 

Low drainage density 

Medium drainage density 

High drainage density 

Drainage density equation

total stream lenth / drainage area

High drainage density are found where?

with little vegetation or very impermeable rocks and/or soils because infiltration and evaporation are low. All precipitation must move as surface water.

As drainage area increases— 

so does the total volume of water or discharge, that the river must transport. 

The shape of a river at a cross section— 

reflects discharge 

Cross section

elevation profile of a water from bank to bank (perpendicular to flow)

DIscharge (L³/T)

volumetric flux of water through a cross section

Velocity (L/T)

how fast the water is moving

Depth (L)

from water surface to bed

Width (L)

bank-to-bank distance

Discharge equation 

Velocity x Depth x Width

Modes of sediment transport

• Bedload 

• Suspended load 

• Dissolved load 

Source 

Where sediments is created and eroded 

Transport 

sediment moves through 

Sink

where sediment is deposited

Weathering

the decomposition of rock into mobile sediment

Erosion

the movement of rock fragments (to rivers)

Source areas

• generally steep mountain regions

• Active tectonic uplift creating steep terrain 

• Course particles (cobbles and boulders) 

• Highest erosion rates because of rapid uplift 

Bedrock rivers 

backs and beds are made of solid rock 

Abrasion-dominated systems

Plucking-dominated systems