Topic 1 Hydrology, River Processes and Hazards Vocabulary

Complete glossary of hydrological and river process terms for A Level Geography.

abrasion

When the load of a river rubs against the riverbed and riverbanks, wearing them down over time.

afforestation

Planting trees in an area that has not recently had tree cover.

agricultural

Relating to farming.

antecedent moisture

The existing level of moisture in soil before precipitation occurs.

baseflow

The very slow movement of water through permeable rock towards a river channel.

bedrock

The solid rock beneath surface materials such as soil and sand.

bluffs

Steep cliffs along the side of a river, which form as the river erodes the lower part of the river bank and the upper part of the river bank then breaks off.

cavitation

A type of erosion where the force of a river traps an air bubble in a small crack in a rock on the riverbed or riverbanks and implodes under the pressure, weakening the rock.

chalk

A soft sedimentary rock, which is a form of limestone.

clay

A soft mineral, which forms soils and many sedimentary rocks.

condensation

The process of water vapour in the atmosphere cooling and changing into liquid water.

corrasion

A type of erosion where the load of a river rubs against and wears down the riverbed and riverbanks over time.

dam

An artificial structure across a river which controls the flow of water.

deforestation

Cutting down trees and clearing an area of forest.

deposition

The process of a river losing energy and dropping the load it has been carrying.

discharge

The volume of river water flowing past a given point at a given time.

drainage basin

An area of land that is drained by a single river and its tributaries.

drainage density

The total length of the channels in a drainage basin divided by the total area of the drainage basin.

duration

In a hydrograph, the amount of time that precipitation lasts.

erosion

The process of material being removed from a riverbed and riverbanks.

evapotransipration

The process of water moving back into the atmosphere by evaporation and transpiration.

falling limb

A part of a hydrograph showing when the discharge of a river decreases and the river level falls.

floodplain

A flat area of land found beside rivers in the middle and lower course.

flood forecast

A prediction of the occurrence, magnitude and duration of a flood.

gauging station

A site on a river where a hydrologist measures the discharge of the river.

gorge

A narrow valley that forms when a waterfall retreats upstream.

granite

A hard igneous rock, formed when melted rock under the Earth's surface cooled and solidified.

groundwater

The water stored in soil or permeable rock under the Earth's surface.

groundwater flow

The very slow movement of water through permeable rock towards a river channel.

hard engineering

Flood management techniques that work against nature.

helicoidal

A river flow pattern, where the water moves in a corkscrew-like motion.

hydraulic action

When the force of moving water removes rocks and sediment from the riverbed/ seabed and riverbanks.

hydrograph

A combined bar and line graph, which shows how a river responds to a period of rainfall.

infiltration

The process of surface water moving into the soil.

inputs

The processes which move water into a drainage basin.

intensity

The strength of a period of rainfall.

interception

The process of vegetation preventing precipitation from reaching the ground.

irrigation

The process of artificially supplying water for crops.

(recurrence) interval

The estimation of the amount of time between flood events of a particular magnitude.

lag time

In a hydrograph, the amount of time between peak rainfall and peak discharge.

laminar

A river flow pattern, where the water moves in smooth and parallel lines.

(river) landforms

The physical features a river creates through the processes of erosion, transportation and deposition.

levee

Higher areas of land found beside a river.

limestone

A soft sedimentary rock, which is made of calcium carbonate.

load

The material that a river transports.

meander

A bend in a river, usually found in the lower or middle courses.

outputs

The processes which move water out of a drainage basin.

overland flow

The movement of water which has entered the drainage basin, such as precipitation, over the ground towards rivers.

oxbow lake

An isolated section of water that is left behind when a meander bend becomes cut off.

percolation

The downward movement of water from the soil into permeable rocks.

permeability

The ability of a rock or soil to allow liquid through it.

point bars

A gently sloping mound of sand, gravel and rocks found in the inside of a river meander, which forms as the river loses energy and deposits material.

porosity

The quality of a rock or soil having tiny holes which allow water to pass through it.

precipitation

Water falling from the air onto the land, for example, rain, snow, and hail.

riffle-pool sequence

Alternating areas of deep, slow-moving water (pools) and shallow, fast moving water (riffles) on a riverbed.

rising limb

A part of a hydrograph showing when the discharge of a river increases and the river level rises.

river straightening

The process of removing meanders from river channels to allow water to move more quickly downstream and reduce the chance of flooding.

riverbank

The land on the edges of a river, which marks the sides of the river channel.

saltation

When small pebbles and stones appear to bounce along the riverbed/seabed.

sandstone

A soft sedimentary rock, composed of sand and other small sediments.

silt

Granular sand, clay and soil that a river carries and deposits.

(diversion) spillway

An artificial channel which a river can flow into when its discharge rises.

soft engineering

Flood management techniques that work alongside nature.

stemflow

The movement of water which has entered the drainage basin, such as precipitation, through the stems of plants into the ground.

suspension

When fine sediment particles, such as silt and clay, are carried along by the river/ sea.

thalweg

The line of fastest flow in a river.

throughfall

The movement of water which has entered the drainage basin, such as precipitation, and drips from the plant canopy into the ground.

throughflow

The lateral movement of water through soil.

traction

When large boulders and rocks are pushed, dragged, or rolled along the riverbed/ seabed by the force of flowing water.

transfers

The processes which move water within the drainage basin.

transpiration

The process of water moving back into the atmosphere as plants lose water through their stomata.

turbulent

A river flow pattern, where the water moves in a swirling, chaotic motion around objects such as rocks.

urbanisation

An increase in the proportion of people living in towns and cities.

velocity

The speed of the water in a river, in a given direction.

water table

The boundary between the soil surface and the underground rocks which are permanently saturated with water.

waterfall

Water flowing over a ledge of harder rock.

wetland

An area of land where water covers and saturates the soil.