Rivers
Opportunities presented by a river
| 2.2 Rivers | |
| Candidates should be able to:Explain the main hydrological characteristics and processes which operate in rivers and drainage basins Demonstrate an understanding of the work of a river in eroding, transporting and depositing Describe and explain the formation of the landforms associated with these processes Demonstrate an understanding that rivers present hazards and offer opportunities for people Explain what can be done to manage the impacts of river flooding | Further GuidanceCharacteristics of rivers (including width, depth, speed of flow, discharge) and drainage basins (including watershed, tributary, confluence) Processes which operate in a drainage basin (including interception, infiltration, throughflow, groundwater flow, evaporation, overland flow) Forms of river valleys-long profile and shape in cross-section, waterfalls, potholes, meanders, oxbow lakes, deltas, levées and flood plains Causes of hazards (including flooding and river erosion) Opportunities of living on a flood plain or a delta or near a river |
| Case Study required for 2.2The opportunities presented by a river or rivers, the associated hazards and their management | |
What opportunities do rivers present?
- Irrigation for agriculture
- Transportation
- Drinking water
- Can have a potential for hydroelectric power from dams
- Flat land in the flood plain for living and making roads/railways etc…
- Making a living as a fisherman or a supervisor for river activities like canoeing, kayaking, canyoning, white water rafting…
Characteristics of rivers in the upper course:
Gradients are steep and the river channels are narrow. The main erosion present in the upper course of the river is vertical erosion and features of this are steep valley sides, gorges and waterfalls.
Transportation
| Type of Transportation | What is it? |
| Solution | Minerals are dissolved in the water and carried along in solution. This typically occurs in areas where the underlying bedrock is limestone or chalk. |
| Suspension | Fine, light material such as alluvium is carried along in the water. This is known as suspended load. The load bounces in line with the rise and fall in the velocity of the river. |
| Saltation | Small pebbles and stones are bounced along the river bed. |
| Traction | Large boulders and rocks are rolled along the river bed. The load carried this way is called bed load. |
Erosion
| Type of Erosion | What is it? |
| Abrasion | When boulders or stones wear away the river banks and beds. It is responsible for vertical erosion and lateral erosion. |
| Attrition | When sediment particles knock against the bed or each other and break, becoming more rounded and smaller as you move down the river. |
| Hydraulic action | When water is pushed into river banks and forced into small cracks in the bedrock and this keeps on happening which makes the crack bigger. |
| Solution | When the acidic water dissolves rock such as chalk or limestone. |
Case Study: Opportunities Provided by Rivers in Tokyo
The Tamagawa river runs from the west to the east into Tokyo bay.
The Sumida river runs from the north to the south into the Tokyo bay.
Direct Opportunities:
Water for irrigation /farming (e.g. rice on Kanto plain)
Water used in industry
Water used for domestic (household use) e.g. Tokyo
Leisure and tourism – especially in Tokyo
Indirect Opportunities:
Provides flat floodplain for building
Fertile floodplain for farming
Flat straight transport route for roads and railways
Hydrological cycle
Key terms: (Erosion)
Hydraulic action – force and impact of water removing material from bed and banks of a river
Solution – rocks dissolved in the presence of water (e.g. limestone)
Attrition – when material wears away the bed and banks
Abrasion – effect of load grinding away bed and banks of river like a sandpaper
Key terms: (Transport)
Suspension – very light materials carried near the surface
Solution – minerals dissolved and carried in solution
Saltation – small pebbles and stones bounced along the riverbed
Traction – heavy boulders and rocks rolled along the riverbed
Lower course features (1)
Oxbow lakes:
Meanders:
Lower course features (2)
Deltas:
Flood plains:
Hazards & management
Hazards:
- Flooding leading to loss of housing
- Loss and diversion of transport routes
- Loss of social, environmental and economic amenities (facilities)
- Stress, injury and death
Management:
- Store of sandbags for emergency use
- A system of sirens and warnings and evacuation procedures
- Temporary, moveable metal barriers that can be put up quickly
Case study: (2019 Tamagawa flood)
| How is Tokyo protected from flooding? | Hard Engineering (try and give specific located examples) | Soft Engineering (try and give specific located examples) |
| 1 | Underground tunnels in Saitama linked to several major rivers. (Build underground as areas above ground are all used for housing etc.) The tunnels fill up during times of flood preventing less water joining the Arakawa and then pump water back into the Edo river after the flood levels have dropped. | Flood plains around Tama river allow for some flooding |
| 2 | Large embankments by flood plains | Afforestation in the upper reaches of the river e.g. Ara river in Saitama |
| 3 | Rivers lined with concrete to manage the flow | Flood water storage spaces are incorporated into building designs |
| 4 | An ‘extra’ river was built onto the Arakawa to divert rivers away from central Tokyo. | |
| 5 | Permeable’ pavements in Tokyo. |
| Evaluation of flood protection in Tokyo | Benefits((give specific detail where possible) | Problems (give specific detail where possible) |
| 1 | Flood tunnels very effective (risk of flooding reduced since completion) | Very expensive and doesn’t protect everywhere. |
| 2 | Increase in typhoons from global warming so ‘strong’ measures needed and the flood tunnels have worked. | Too much hard engineering – not sustainable. |
| 3 | Flood plains create recreational spaces. | Problem of flooding still exists – has Tokyo done enough? |
| 4 | People can cycle along embankments and there are often areas for doing Hanami | Concrete lining of rivers increases the chance of flooding downstream. |
| 5 | Hard engineering disturbs natural habitats/wildlife |
Still got a question? Leave a comment
Leave a comment