Rivers

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Rivers

rivers.pdf
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Water Cyle

Complete the water cycle diagram and worksheet

Water Cycle Worksheet
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The Drainage Basin as a system

How does the water cycle work?

Energy from the Sun heats the surface of the Earth.
Water is evaporated from oceans, rivers, lakes, etc.
The warm, moist air rises because it is less dense.
Condensation occurs when water vapour is turned back into water droplets as it cools down. Clouds are formed.
Precipitation occurs as water droplets get bigger and heavier they begin to fall as rain, snow and sleet, etc.

When the precipitation reaches the surface, some falls directly into the sea but other water falls on land:

Some water is intercepted by vegetation. Some water may then slowly reach the ground. Some will evaporate from the surface of leaves or be taken up by the plant roots, and some of this water will eventually return to the air as vapour through the process of transpiration. This slows down or prevents some water flowing back to the river.
Some water flows across the surface of the ground – surface run-off. This happens when the surface doesn’t allow water to penetrate. Surface run-off is more likely to occur if the ground is saturated with water or when the rock is impermeable. This water moves quickly to the river.
Some water infiltrates into the soil. This through flow moves more slowly back to the river than surface run-off.
Some water percolates deeper into the ground and is slowly transferred back to the river or sea.

Stores and transfers
The major stores of water are the ocean, ice caps, land and the atmosphere. The movement of water between these stores is called transfers.

Define the key words for the drainage basin system.

Print and complete the above diagram

Drainage Basin

Drainage basin diagram

Define the key words on the drainage basin diagram

River Processes

The River processes are the same as we looked at in the Unit of Coasts. You have already learnt this so all you need to do is remind yourself of the forms of Erosion and Transportation that you have looked at.

IGCSE COASTS

The four types of erosion

Long River profile

Long River Profile

River Features along the river profile

geographyalltheway.com - IB Geography - The Bradshaw Model from geographyalltheway.com

Waterfalls

Waterfall diagram

Formation of a waterfall:

The soft rock erodes more quickly, undercutting the hard rock.
The hard rock is left overhanging and because it isn’t supported, it eventually collapses.
The fallen rocks crash into the plunge pool. They swirl around, causing more erosion.
Over time, this process is repeated and the waterfall moves upstream.
A steep-sided gorge is formed as the waterfall retreats.

V-Shaped Valleys & Interlocking Spurs

V shaped valleys and interlocking spurs from Steven Heath

V-Shaped valley diagram

When a river is near its source, it often develops a V-shaped valley as the river erodes down (this is called vertical erosion). At the same time, weathering breaks up material on the valley slopes. Weathered material from the valley sides gets deposited in the river. This material is carried by the river and erodes the riverbed through abrasion.

Meanders and Oxbow Lakes

Meander: is a bend in the river. Meanders usually occur in the middle or lower course, and are formed by erosion and deposition.

Meander Animations

Meander Animation Link

Meander cross section

As the river erodes laterally, to the right side then the left side, it forms large bends, and then horseshoe-like loops called meanders.
The formation of meanders is due to both deposition and erosion and meanders gradually migrate downstream.
The force of the water erodes and undercuts the river bank on the outsideof the bend where water flow has most energy due to decreased friction.
On the inside of the bend, where the river flow is slower, material isdeposited, as there is more friction.
Over time the horseshoe become tighter, until the ends become very close together. As the river breaks through, eg during a flood when the river has a higher discharge and more energy, and the ends join, the loop is cut-off from the main channel. The cut-off loop is called an oxbow lake.

Floodplains

Watch the following animation and explain: What are floodplain and how do they form?

Levees

Levee diagram

River Deltas

Print and complete the River Delta Worksheet

River Deltas Worksheet
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Why do people live near rivers?

Benefits
Floodplains are dynamic natural systems. The natural processes of periodic flooding, accompanied by erosion and deposition, bring changes to the topography, soils, vegetation, and physical features (such as meanders, braided channels and oxbow lakes) within these areas over time.

Floodplains provide a wide range of benefits to the ecosystem and community that include:

Flood storage and erosion control–offer a broad area for streams and rivers to spread out and accommodate temporary storage of flood water, reducing flood peaks and erosion potential
Water quality maintenance – reducing sediment loads, filtering nutrients and impurities, and moderating water temperature
Groundwater recharge
Biological productivity – providing fertile soils with high rate of plant growth and diversity, richer agricultural harvests, and healthier forests
Habitat for a variety of fish and wildlife, including rare and endangered species
Recreational opportunities – providing areas for active and passive activities, supporting the economic base
Open space

Causes of Floods

What causes a flood? from Steven Heath

Storm Hydrograph
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Create a brief Video using a hand drawn model explaining:
What a storm Hydro-graph is and how it works.
What factors, Physical and Human cause flooding.

Factors that Cause Flooding

River Management Strategies

Using the following three websites create a table listing, describing and explaining the possible management strategies for rivers and their floodplains. Separate them into Hard and Soft Engineering strategies.

River Flood Case STudy

Case Study: Mississippi River

Describe the location of the Mississippi River.
Outline the benefits and opportunities of living near the river - what activities happen near on around the Mississippi?
What happened in he 2011 river flood?
How is the Mississippi river being managed?