Rivers - pg 69-74 in resource binder

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What is the hydrologic cycle?

The continuous movement of water from sea to land and back to sea, and from water to water vapour and back to water.

What is transpiration?

The process by which vegetation returns moisture to the atmosphere.

What are the three possible outcomes when precipitation reaches the ground?

(i) It may evaporate, having no effect on gradation; (ii) If the ground is porous, it may soak in and weather rock by solution; (iii) If the ground is impervious, it may drain off as runoff and help form a stream or river.

What can happen if porous rock lies on top of impervious rock?

The porous layer can become saturated with groundwater, which may flow out as a spring.

What is a spring?

A natural source of water that flows out of the ground, often forming the source of a stream.

What determines a river’s ability to carry weathered materials?

Its velocity and volume.

What three processes of the cycle of gradation does a river involve?

Weathering, transportation, and deposition.

Define a river or stream.

A flow of water that has been channelled and follows a definite course.

What is the head or source of a river?

The place where it first appears as a surface stream; the highest point of a stream.

What is the mouth of a river?

The point where the river ends, either by entering a sea, a lake, or joining another river.

What is a river system?

A main stream and its tributaries.

What is a drainage basin?

The land drained by one river system.

What is a watershed or divide?

The height of land separating two drainage basins.

What is a river valley?

The elongated depression in which a river flows.

What is the bed of a river?

The part of the valley actually covered by the river.

What are river banks?

The higher areas on either side of the river bed.

What are levees?

Extra high banks created by deposition.

What are dikes?

Man-made levees.

What does downstream mean?

Towards the river’s mouth.

What is corrasion?

The erosive action that occurs as particles in the river wear away surfaces they pass over.

What is solution (erosional transport)?

Sediment dissolved in the river.

What is suspension?

Materials not dissolved but carried in the middle of the river.

What is saltation?

Materials rolling along the river bottom.

What are the three stages of river development?

Young (upper course), mature (middle course), and old (lower course).

What are the characteristics of a young river?

Steep gradient, medium discharge, medium velocity, vertical erosion, and features like waterfalls, gorges, and rapids.

What are the human uses of a young river?

Tourism, drinking water, and hydroelectric power.

What are the characteristics of a mature river?

Medium gradient, high velocity, heavy sediment load, lateral erosion, V-shaped valleys, and flood plains.

What are the human uses of a mature river?

Farming, housing, transport, fishing, and hydroelectric power.

What are the characteristics of an old river?

Low gradient, high discharge, slow velocity, wide flood plains, meanders, yazoo streams, large levees, oxbow lakes, and deltas.

What are the human uses of an old river?

Farming, housing, and transport.

What does discharge mean?

The volume of water flowing in a river.

What is a gorge?

A deep, narrow valley through which a stream flows.

What is a yazoo stream?

A tributary that meanders oddly on a flood plain, eventually breaking through levees to join the main river.

What is an oxbow lake?

The cut-off portion of a meander, indicating poor drainage; marshes or swamps are often nearby.

What is meant by river complexity?

Every river is a complex system seeking balance among variables such as discharge, sediment load, and velocity.

What happens upstream of a hydro dam?

Discharge increases (formation of lake), sediment is trapped, erosion and transport decrease, channel width/depth increase, velocity and gradient decrease.

What happens downstream of a dam?

Discharge may decrease or stay the same; sediment load decreases; less erosive power and lower velocity.

How does clearcutting affect a river?

Increases runoff, sediment load, velocity, and erosion; channel roughness may increase near the clearcut.

What are some advantages of dams?

Flood control, irrigation, hydroelectricity, water storage, and recreation (boating, fishing, swimming).

What are some disadvantages of dams?

Destruction of habitats, drying wetlands, sediment buildup clogging turbines, reduced downstream nutrients, and potential earthquakes.

What is dendritic drainage?

A drainage pattern where streams form a branching, leaf-vein pattern on rock of uniform hardness.

What is trellis drainage?

A pattern where main streams flow in valleys with tributaries joining at right angles, resembling a garden trellis.

What is radial drainage?

A pattern where streams flow outward from a central high point such as a volcanic cone or dome.