Unit 1, hydrology and fluvial geomorphology

Question 1

Outputs of the drainage basin

Answer 1

Transpiration, evaporation, river channel flow.

Question 2

Inputs of the drainage basin

Answer 2

Precipitation.

Question 3

Stores of the drainage basin

Answer 3

Interception, surface storage, soil moisture storage, groundwater storage, channel storage.

Question 4

Flows of the drainage basin

Answer 4

Overland flow, infiltration, percolation, throughflow, groundwater flow.

Question 5

Components of hydrographs

Answer 5

Discharge, rising limb, falling limb, peak discharge, lag time.

Question 6

Discharge definition

Answer 6

Amount of water passing every second.

Question 7

Rising limb definition.

Answer 7

The rapid increase in resulting from rainfall causing overland flow.

Question 8

Falling limb definition

Answer 8

When discharge decreases and the river’s level falls.

Question 9

Peak discharge definition

Answer 9

Time of the highest river channel level.

Question 10

Lag time definition

Answer 10

The amount of time between the peak amount of rainfall and the peak discharge in the river.

Question 11

Influences on hydrographs

Answer 11

Shape of the drainage basin, heavy storms, snowfall, vegetation, rock type, deforestation, afforestation, urbanisation, reservoirs, agriculture.

Question 12

How does climate and temperatures affect a storm hydrograph?

Answer 12

Hot, dry conditions and cold, freezing conditions result in hard ground, reducing infiltration and increasing surface runoff, this leads to a reduced lag time and peak discharge. High temperatures can also increase evapotranspiration, reducing the amount of water reaching the river channel and peak discharge.

Question 13

Drainage basin characteristics

Answer 13

Size, shape, slope, rock type, soil type, drainage density, rainfall type and rainfall intensity.

Question 14

Basin size

Answer 14

A large drainage basin will mean that water takes a long time to travel through tributaries or the ground to reach the channel.

Question 15

Basin Shape

Answer 15

Circular basins mean shorter lag times and higher peak discharges and elongated basins, longer lag times and lower peak discharges.

Question 16

Slope

Answer 16

A steeply-sided river valley means that gravity assists water in its descent towards the river channel, whereas gently sloping valleys tends to produce longer lag times and lower peak discharges.

Question 17

Rock type

Answer 17

Permeable rocks such as chalk and limestone infiltrate water so longer lag times and lower peak discharges, and impermeable rocks such as granite and clay allow water to continue to move so this results in shorter time lags and higher peak discharges.

Question 18

Soil type

Answer 18

Sandy soils have high rates of infiltration due to relatively large air spaces or voids between soil particles, whereas clay soils and silts have small pore spaces which allow very little throughflow.

Question 19

Drainage density

Answer 19

Basins with impermeable rocks and soils are those with a high drainage density, whereas basins with permeable ones are those with a low drainage density.

Question 20

Rainfall type

Answer 20

Snow intercepts water, long periods of rainfall leads to soil saturation and therefore overland flow and a basin with lots of vegetation will experience high rates of interception so therfore there would be a longer lag time and a lower peak discharge.

Question 21

Rainfall intensity

Answer 21

Heavy rainfall may exceed the infiltration capacity of the soil, leading to surface runoff and a rapid increase in discharge.

Question 22

Channel processes

Answer 22

Erosion, transportation and sedimentation.

Question 23

Erosion

Answer 23

Four ways:

• Abrasion - large pieces wear away the river banks and bed.
• Attrition - sediment particles knock against the bed or each other and break, becoming more rounded and smaller.
• Hydraulic action - the force of water erodes softer rock.
• Corrosion - acidic water erodes rock.

Question 24

Transportation

Answer 24

Four ways:

• Solution - minerals are dissolved and carried along.
• Suspension - fine, light material is carried along in the water.
• Saltation - small pebbles and stones are bounced along the river bed.
• Traction - large boulders and rocks are rolled along the river bed.

Question 25

Sedimentation

Answer 25

Rock fragments produced by the weathering of geological features.

Question 26

Channel types

Answer 26

Straight, meandering and braided.

Question 27

Meandering

Answer 27

Rivers flowing over gently sloping ground begin to curve back and forth across the landscape.

Question 28

Braided

Answer 28

A network of river channels separated by small, often temporary, islands.

Question 29

Landforms

Answer 29

Potholes, rapids, waterfalls, meanders, levees, flood plains and deltas.

Question 30

Potholes

Answer 30

Irregular hollow that is usually deeper than wide formed in the rocky bed.

Question 31

Rapids

Answer 31

Sections of a river where the river bed has a relatively steep gradient, causing an increase in water velocity and turbulence.

Question 32

Waterfalls

Answer 32

An area where water flows over a vertical drop in the course of a stream or river. They are created when the riverbed changes suddenly from hard rock to soft rock.

Question 33

Meanders

Answer 33

One of a series of regular sinuous curves in the channel of a river, They are formed as a river erodes the sediments comprising a bank and depositing this downstream.

Question 34

Leeves

Answer 34

An elongated naturally occurring ridge or artificially constructed fill or wall that regulates water levels.

Question 35

Flood plains

Answer 35

A flood plain is an area of flat land alongside a river. This area gets covered in water when the river floods.

Question 36

Deltas

Answer 36

Wetlands that form as rivers empty their water and sediment into another body of water, such as an ocean, lake, or another river. The three main types of deltas are the arcuate, the bird’s foot and the cuspate.

Question 37

Modifications to flows

Answer 37

Building dams to trap water from rivers, pumping water from the ground, and dredging for new sources of water.

Question 38

Dams

Answer 38

A structure built across a river or stream to hold back water.

Question 39

Causes of floods

Answer 39

Heavy rainfall, ocean waves coming on shore, melting snow and ice, dams or levees breaking.

Question 40

Impacts of floods

Answer 40

Loss of human life, damage to property, destruction of crops, loss of livestock, non-functioning of infrastructure facilities and deterioration of health condition owing to waterborne diseases.

Question 41

Forecasts

Answer 41

A process of estimating and predicting the magnitude, timing and duration of flooding based on known characteristics of a river basin, with the aim to prevent damages to human life, to properties, and to the environment.

Question 42

Warnings

Answer 42

You should do all the actions for a flood alert but also: move vehicles to higher ground if it’s safe to do so. move family and pets to safety.

Question 43

Hard engineering

Answer 43

Can involve raising the height of river banks by installing flood walls, bunds and levees which attempt to fix the river in place, stopping the natural process of the river overtopping and flowing onto the floodplain.

Question 44

Soft engineering

Answer 44

Natural processes along the river to reduce the effects of flooding. Soft engineering warnings include flood warnings, preparation, flood plain zoning, and simply doing nothing.