RiversRivers

What is a River? Simply put, a river is a channel that carries water. But a river is much more than that- it is part of a system. A river is a system of tributaries that drain an area of land into a main channel. A river carries water from its source in the highlands to its mouth at a lake, sea, or ocean.

A river is all about energy. If a river is moving fast (due to gravity) and has a lot of water – it has great energy. With great energy comes erosion and the transport of the eroded material. With a loss of energy comes deposition.

EnergyEnergy Features due to erosion or deposition depending on speed. Low energy/low speed = deposition High energy/high speed = erosion

Stages of River Development A: Youthful/Upper Stage B: Mature/Middle Stage C: Old/Low Stage

Stages of River Development YouthfulOld AgeMature

Stages of River Development

A: Youthful Stage Steep, fast, straight, vertical erosion V-Shaped valleys Waterfalls, rapids

B: Mature Stage Less steep, slower, horizontal erosion Valley becoming flat River begins to meander

C: Old Age Stage Flat, slow meandering, depositional Wide flood plain Ox-bow lakes begin to form

Drainage Basins Area in which all raindrops eventually drain into the same river system, ocean, or lake (catchment, watershed) Which Drainage Basin does Sioux Lookout belong to? Canada’s Drainage Basins

Drainage Basins Tributaries: smaller rivers that drain into larger rivers. Interfluves: pieces of higher land between tributaries. Divide: higher ground between drainage basins.

Drainage Patterns There are 5 Drainage Patterns: –Dendritic –Trellis –Radial –Rectangular –Deranged

Drainage Patterns

Dendritic Drainage Pattern Flow across level land, merging with other rivers Resemble branching tree

Trellis and Rectangular Ground is made of folded bedrock, rivers may follow a straighter course along the softer bedrock, with hard rock on either side. Often in mountainous areas. Trellis: one main trunk Rectangular: square pattern

Rectangular Trellis

Radial Pattern Landforms influenced by volcanoes and cone-shaped hills. Streams radiate outward in all directions from central zone

Deranged Pattern No distinct pattern noted Often lakes are found throughout Glaciation has torn the landscape leaving this deranged pattern Common in NW Ontario!

LEVEES Form on floodplains when rivers flood. Water quickly loses its velocity as it spreads out from the channel and deposition occurs Heavier sediments tend to settle out immediately close to the channel and an area of slightly higher ground is built up on both sides of the river Because of levees, the river channel is often built up higher than the floodplains, which is then very susceptible to flooding Geomorphological Features

Below is a picture of Wilket Creek in Toronto. It flooded during a violent storm in What you see is the sediment that the river was carrying when it flooded. Note that the sides have heavy material and the interior is very sandy. The River could not carry the heavier rocks.

Natural levees have been built up by man for flood control.

Meanders and levees, Red River flood, Manitoba,

FLOODPLAINS  Valley area through which a river flows in the mature (old age) stage Built by river depositing material on the insides of the bends as it meanders and when finer materials are deposited on the valley floor when the river floods. Finer materials traditionally added nutrient value to the soil and thus helped to make floodplains very fertile areas, supporting large populations Unfortunately, large floods also usually meant a loss of life as well. A few floodplains support a large portion of the world’s population: Hwang Ho, Yangtze, Indus, Ganges and the Nile.

A Landsat 5 image taken Sept shows a section of the Missouri River. The oblique perspective of this image is looking upstream. This image has been color enhanced and modified to show an exaggerated topographic relief. Bare soil and plowed land appears red, vegetation appears green, and water is dark blue. A flat river flood plain can be seen in the center of the image. Because of the season, most of the farmland located on the rich and fertile soils of the floodplain is plowed and devoid of vegetation.

Meander:Meander: back and forth sweep of a river in old age. As a river reaches its mature stage its ability to erode diminishes and whenever it does erode material it will quickly deposit that material. As it erodes material from one bank (on the outside - Pool) it deposits material on the other bank (the inside - Riffle) and river begins to bend or meander.

Example of a Pool and Riffle from the Don River

Oxbow lakes:Oxbow lakes: an area of poor drainage that occurs when a meander is cut off from the main river channel, forming a lake.

Delta:Delta: depositional feature found at the mouth of a river. River’s water reaches mouth of river and the sediment is carried settles.

This is the mouth of the Humber River (flowing into Lake Ontario). Notice the width of the river and the flow is very slow.

This is near the mouth of the Humber river. Notice under the bridge the ‘Bulrushes’. This area is also called the Humber Marsh. The river has slowed down and has deposited some silt or dirt, allowing the vegetation to grow.

Estuary:Estuary: the flooded mouth of a river valley. If there is an ocean involved we get a mixture of fresh and salt water.