Key Vocab

• Relief

  Height, shape, and steepness of the land
• Hydraulic Action

  The force of the water hitting the river bed and banks. This is most effective when there are large quantities of fast moving water.
• Abrasion

  When the load carried by the river repeatedly hits the bed or banks, dislodging particles into the flow of the river.
• Attrition

  When stones carried by the river knock against each other, gradually making them smaller, smoother, and rounder.
• Solution (erosion)

  When the river flows over limestone/ chalk, the rock is slowly dissolved, as it is soluble in mildly acidic river water.
• Solution (transportation)

  Minerals are dissolved in the water due to chemical change.
• Traction

  Large boulders and rocks are rolled along the river bed.
• Saltation

  Small pebbles and stones are bounced along the river bed.
• Suspension

  Small sediment held in the river.
• Meander

  A bend in a river, mainly found in the middle course of a river and in lowland area.
• Thalweg

  The fastest flow of the water.
• River velocity

  How fast the river is flowing

  The speed of the river water
• River discharge

  Volume of water flowing through a river channel
• River capacity

  Maximum value of water a river can carry
• Slope gradient

  How step the land is. The speed of water flow increases as the slope gradient becomes steeper.
• Rock permeability

  How easy it is for water to get into cracks and pass through rocks due to precipitation. The more porous a rock is, the more permeable it is.
• Evaporation

  Process of water becoming vapour. It moves from the earth's surface to the atmosphere.
• Saturation

  Ground exceeding water capacity.
• Infiltration

  The movement of water down through the soil. This takes a long time.
• Transpiration

  Loss of water vapour through plants.
• Interception

  Precipitation that doesn't reach the soil, but is instead intercepted by leaves, branches, or trees.
• Groundwater flow

  The movement of water along soil and rock.
• Throughflow

  The movement of water along soil.
• Perculation

  Movement of water down through rocks.
• Flooding

  Where land which is not usually underwater becomes inundated (overwhelmed),so the channel can no longer hold the amount of water flowing in it as it has exceeded river capacity, os the water over tops the banks and floods over the land onto the flood plains. They usually occur ter long periods of rain, which are often in winter months, or in torrential storms in summer, leading to flash floods.
• Levee

  Naturally raised river beds, fund on both sides or either side of a river channel that is prone to flooding.
• Flood plain

  Wide, flat area on marshy land on either side of a river in the middle and lower course.
• Estuary

  Found at the mouth of the river, where the river meets the sea. The water is tidal, and floods over the banks of the river carrying silt and sand on the valley floor. As the tde reaches its highest point, the river water is moving slowly as the velocity decreases, so the sediment is deposited. The process repeats over time, with more mud build up, forming mud flats, which when left exposed, lead to the formation of salt marshes.