Rivers

• Erosion: the process that wears away the river bed and banks
• Transportation: It carries and transports the rock
• Deposition: Then they drop or deposit it
• Types of erosion: abrasion, attrition, hydraulic action, solution
• Abrasion: wearing away of the bed and banks by the load of a river, when waves pick up rocks and other material and throw it onto a coastline, causing parts of the cliff to dislodge
• Attrition: wearing away of rock, usually causing small and rounded pebbles
• Hydraulic action: when air gets trapped in cracks and gets compressed, the power of breaking waves causes it to erode
• Solution: when weak acid in the water dissolves minerals in the rocks
• Traction: Larger rocks are picked up and rolled along the riverbed 
• Saltation: Smaller stones are picked up and bounced along the riverbed
• Types of transportation: Traction, saltation, suspension, solutions
• Suspension: lighter sediment is suspended and transported along the river 
• Solution: Weak acid dissolved minerals in the rocks
• Weathering: to wear away or change the appearence or texture of something by long exposure
• Bradshaw model

  
• V-shaped valley (upstream): this is downwards erosion and weathering that makes the river bed deeper. It is usually caused by hydraulic action and occurs in the upper course of the river, causing steep-sided v-shaped valleys.
• Gorge (upstream): a deep, narrow valley with steep sides, usually formed by a river or stream cutting through hard rock.
• Waterfall formation (upstream):

  The softer rock erodes faster than harder rock. The is done by hydraulic action and abrasion. These processes cause the softer rock to be worn away and removed quicker than the harder rock, so an overhang of hard rock is formed. Because it's unsupported the overhang will collapse. A plunge pool forms at the base of the waterfall due to the erosion of the collapsed material and the hydraulic action of the river flow. Harsh water in the plunge pool causes undercutting. The process repeats, and the waterfall retreats upstream. Over time, this can form a gorge.

  
• Drainage basin: the area of land that is drained by a river and its tributaries. The dividing line between drainage baisins is called the watershed

  
• Interlocking spurs (upstream): In the upper course of the river the channel starts to meander, because the river doesn't have much power here to erode so it will wind it's way around hard rock. This happens upstream
• Meanders (middlestream): Meanders are formed in the middle course of a river. As the river gains more velocity, the water is pushed to the outside of the river causing more erosion on the outside bend, which forms a steep river cliff. This happens through hydraulic action and abrasion. Water on the inside of the bend of the river has a lower velocity because there is more friction. Therefore, the water starts to deposit eroded materials, creating a slip off slope.
• Ox-bow lakes (middlestream): With distance downstream the size of the meanders increase. The erosion on outside bends can eventually lead to the formation of a meander neck. At a time of the flood, where the water is at high energy, the river may cut through the neck of the meander forming a straighter course for the water. The flow of water at entry and exit from the meander will be slower, leading to deposition. The meander becomes cut off from the main river channel, forming an ox-bow lake.

   

  
• Floodplains and Levees (lowstream): Floodplains are flat expanses of land either side of the river. The migration of meanders leads to the formation of the floodplain. High discharge may cause the river to overflow the banks. Increased friction reduces velocity and material is deposited across the floodplain gradually increasing the floodplain height. The heaviest material is deposited first nearest to the river channel forming natural embankments called levees.
• Distributaries: rivers that leave the main channel and don't return to it
• Eyots/aits: Small islands formed by deposition, near mouth of river
• Deltas (lowstream): Deltas are formed at river mouths. Rivers carry a lot of sediment, when the river flows into a calm sea, it slows down, making it drop it's sediment. This deposited sediment builds up over years creating a delta, the river is forced to split up and the smaller rivers made by deltas are called distributaries
• Pothole: circular hole formed in rocky bed by abrasion and circular currents
• Watershed: the area of high land forming the edge of a drainage basin
• Tributary: A stream or river which joins another larger one
• Confluence: The point which two rivers meet
• Through flow


  Water flows through soil towards rivers and lakes after it sneaks into soil (infiltration)
• Overland flow


  Rainfall flows over the ground towards rivers and lakes, this is the main cause of flash floods
• Groundwater flow

  Some water seeps into the rock below soil and flows very slowly in cracks and pores
• Condensation


  When water vapor cools down again, tiny water droplets form and become visible as clouds
• Evaporation


  Water returns to the atmosphere in a vapor form once it is heated by sunlight
• Precipitation


  Tiny water droplets collide and grow and fall to the ground as rain or snow
• Transpiration


  Water is lost through small holes in the plant and evaporation from trees
• Infiltration


  Water moves from the surface downwards into the soil
• Discharge: the amount of water flowing in a river

  Discharge: cross sectional area x river velocity
• Hard engineering: methods of river management that are expensive, effective and impactful on environment