Section C - River Landscape Flashcards
What are the inputs and outputs in a Hydrological Cycle?
Inputs- Precipitation
Outputs- Evaporation, Transpiration, River Flow to the Sea
What are the flows in a Hydrological Cycle?
Flows- Infiltration, Percolation, Through Flow, Groundwater Flow, Surface Runoff
What are the stores in a Hydrological Cycle?
Stores- Interception, Surface Storage, Soil Moisture, Ground Water
Name and explain the 4 types of river erosion processes.
Hydraulic Action- The force of the river water colliding with rocks breaks rock particles away from the river channel.
Abrasion- Eroded rocks picked up by the river scrape and rub against the channel, wearing it away. Most erosion happens by abrasion.
Attrition- Eroded rocks picked up by the river crash into each other and break into smaller fragments. Their edges also get rounded as they rub together. The further material travels, the more it is eroded - attrition causes particle size to decrease from a river’s source to its mouth.
Solution- River water dissolves some types of rock, e.g. chalk and limestone.
Name and explain the 4 types of river transportation processes.
Traction- Large particles like boulders are pushed along the river bed by the force of the water.
Saltation- Pebble sized particles are bounced along the river bed by the force of the water.
Suspension- Small particles like silts and clay are carried along by the water.
Solution- Soluble materials (e.g. limestone) dissolve in the water and are carried along.
What are the two upper course features?
Waterfall/Gorge and V-shaped Valleys/Interlocking Spurs
Explain how waterfalls and gorges are formed.
Waterfall / Gorge- Waterfalls form where a river flows over an area of hard rock followed by an area of soft rock and since soft rock erodes quicker it creates a plunge pool. As the waterfall retreats, this leaves back a gorge.
Explain how V-shaped Valleys and Interlocking Spurs formed
V-shaped Valleys / Interlocking Spurs- In the upper course of a river most of the erosion is vertically downwards, this creates steep v-shaped valleys. The river lacks the energy to erode laterally, so it winds around the high hillsides.
What are the two middle course features?
Meanders and Ox-bow lake
Explain how Meanders are formed
Meanders-Rivers develop large bends called meanders in their middle and lower courses, in areas where the channel has both shallow and deep sections.
Explain how Ox-bow lakes are formed
Ox-bow Lakes- Erosion causes the outside bends to get closer until it forms a small piece of land left called a neck then the river breaks through the land during a flood and flows along the shortest course causing deposition to eventually cut off the meander forming an ox-bow lake like the ones in River Calder
What are the three lower course features?
Levees, Floodplain, Estuaries
Explain how Levees are formed.
Levees- are natural embankments found along a channel edge where heavy material is deposited during a flood on the edges and this process repeats until forming Levees
Explain how floodplains are formed
Floodplains- are wide flat areas of land that flood
Explain how estuaries are formed
Estuaries- found at the river mouth where the river meets the sea. At high tides, silt and sand are carried onto the valley floors and at low tides, it reveals the mudflats
River Jubilee Case Study- Location?
The Jubilee River is a relief channel for the River Thames in southeast England. The relief channel runs through Berkshire and Buckinghamshire, flowing roughly parallel to the River Thames.
River Jubilee Case Study- Purpose?
This area of the Thames flood plain is low-lying and prone to flooding. The impermeable surfaces of the built-up areas have historically resulted in flooding following high rainfall events. Given the high-value property in this area, the EA decided to increase the level of flood protection.
River Jubilee Case Study- Explain this strategy of the flood relief channel.
The Jubilee River was created to take overflow water from the River Thames in times of high discharge following heavy rainfall.
River Jubilee Case Study- Economic Benefits and Issues
The weirs in the river were damaged after 1 year and had to be repaired for £680,000. At a projected cost of £330 million, the Jubilee River was one of four flood-relief channels planned for the lower course of the Thames. However, the EA ran short of funds. If further engineering is to alleviate flooding downstream, local councils and businesses will have to make up a £110 million shortfall. Is this fair, when Windsor and Eton residents did not have to pay? Until a solution is found, small businesses such as shops stand to lose money, as they cannot open when their premises are flooded. Insurance costs are high.
River Jubilee Case Study- Environmental Benefits and Issues
In 2014, there was extensive flooding immediately downstream from where the flood-relief channel rejoined the Thames. The built environment suffered from flooded roads and buildings. Fields were inundated and habitats were disturbed. The concrete weirs are rather ugly, especially under normal flow conditions, when more concrete is exposed. Ongoing repair work has made the matter worse, such as at Manor Farm Weir. There is also the problem of algae collecting behind the weirs. This disrupts the natural ecosystem.
River Jubilee Case Study- Social Benefits and Issues
3000 Wealthy houses protected. The Thames at Old Windsor now suffers from a much higher discharge due to the merging of the two channels just upstream. 2014 flood showed this.
What are the 4 Hard Engineering and the 4 Soft Engineering methods in River Management?
Hard- Dams and Reserviour, Channel Straightening, Embankments, Flood-relief channels
Soft- Flood Warnings and Preparations, Flood plain Zoning, Planting Trees, River Restoration.
Explain Dams and Reserviour and mention the Benefits and Disadvantages
What is it- Dams are barriers built usually in the upper course. A reservoir is an artificial lake behind the dam
Benefits- Reserviours store water, control water flow and prevent floods downstream. Also used for hydroelectric power HEP
Disadvantage- Is Expensive and reservoirs can flood existing settlements. Materials are deposited in reservoirs so farmland downstream can become less fertile.
Explain Channel Straightening and mention the Benefits and Disadvantages
What is it- Meanders are removed to build straighter channels
Benefits- Water leaves more quickly rather than building up so flood risk is lower
Disadvantage- Flooding may happen downstream and fast-moving water increases erosion downstream
