Rivers

rivers

HideShow resource information

Key Words

Base Flow = part of rivers discharge that is produced by groundwater seeping into the river bed

Channel Store = water stored in river store

Channel Flow = water flowing in a river

Evaporation = change of water from liquid to gas

Groundwater Flow = water flowing through rocks towards the river

Groundwater Store = water stored in permeable rocks below the surface of the ground

Infiltration = process where water enters soil

Interception = precipitation that is trapped and stored temporally on the vegetation

1 of 15

Overland Flow = movement of water over the surface of the ground to the river

Percolation = water draining through rocks

Precipitation = water and ice that falls from the clouds in the drainage basin

Runoff = total discharge from drainage basin

Soil Water Store = water stored in the soil

Stemflow = precipiation that runs down stems and tree trunks to the ground

Surface store = water lying on the ground

Throughfall = precipitation that drips through vegetation into the ground

2 of 15

Throughflow = water flowing through the soil

Transpiration = evaporation of moisture from vegetation into the atmosphere

Vegetation = water stored within plants and trees

Water Balance = shows the state of equillibrium in the drainage basin between the inputs, outputs and changes in storage

Storm Hydrograph = shows variations in the rivers discharge over a short period of times

River Discharge = volume of water passing through a point in the river and is measured in cumecs

Rising Limb = indicated highest flow in river and a rise in discharge

Recessional Limb = shows fall in discharge

3 of 15

Lag Time = time decay between max rainfall and and peak discharge

Rejuvenation = fall i the sea level relative to the level of the land or a rise of the land level relative to the level of the sea

Knickpoint = steepening of the long profile

Potential Energy = results of the weight of the water

Kinetic Energy = produced by gravity energy

Lateral = sideways

Abrasion = erosion of the bed by the bedloads

Corrosion = chemical reaction that dissolves the river bed

4 of 15

Hyrdaulic Action = sheer force of water onto the river bed, cracking the river

Attrition = erosion of other bed load

Capactiy = how much a river can carry

Competence = the diameter of the largest particle that a river can carry

Traction = movement of large bedload by rolling along the river

Saltation = movement of bedload by bouncing along the river

Suspension = smaller particles float in the water

Solution = chemical load that has been dissolved into the river

Bedload = material lying on the bed of the channel

5 of 15

Cross Profile = view of the valley from one side to the other

Discharge = cross sectional area times velocity

Hydraulic Radius = cross sectional area divided by wetter perimeter

Velocity = measured in m/s

Wetted Perimeter = length of channel along the cross profile that is in contact with the water

Braiding = occurs when a river is forced to divide into several channels

Delta = caused by depositions

Floodplain = the area onto which the river floods

Levee = build up of coarser sediment on the banks of a river

6 of 15

Meander = bend in the river due to erosion on the outside and deposition on the inside

Pothole = rounded hole in the river caused by abrasion

Rapid/Waterfall = break in the slope along the river profile

Knickpoint = break in the gradient marked by rapids/waterfalls

River Terraces = the remnants of the former floodplain, they create steps in the floodplain

Incised Meanders = deeply cut into the landscape and marked by cliff like banks on either side on the river

Flood Frequency = records past floods and predicts recurrence

Flood Magnitude = severe floods occur less frequently and their likelihood is estimated

7 of 15

Inputs: rain, snow, fog, sleet
Stores: puddles, lake, reservoirs
Throughputs: groundwater flow, river flow, infiltration, interception, surface runoff
Outputs: evaporation, transpiration, river mouth to sea

Drainage Basin is the catchment area from which a river system obtains its water and the Watershed in the imagionary line that determines one drainage basin from another.

Water surplus/ Water deficit

Potential Evapotranspiration is where the maximum amount of evaporation occurs.

Channel Catch = rain which falls directly into the river
Intensity = amount of rainfall in one hour

8 of 15

Temporary Factors Affecting River Discharge :

- climate, precipitation, time of year, type of precipitation and type of rainfall

Permanant Factors Affecting River Discharge:

Basin size and shape, slopes, altitude, drainage density, soil type, geology, river gradient

Depressions = low pressure systems, which from when a tropical air mass meets a polar air mass.

Isobars show strong winds
Warm Front occurs when warm air rises over cooler air
Cold Front occurs when warm air mass is undercut by a cold air mass

Climate is average and Weather is the day to day conditions

9 of 15

Deforestation will increase runoff as the precipitation is intercepted by forest trees which stops the moving water. However surface runoff is reduced as evaporation takes place and rainfall is intercepted by vegetation

Urbanisation - there is more urban development as people are developing their gardens and drive to concrete stopping interception which leads to flooding

Laminar flow is where water particles glide past each other smoothly creating a straight channel with shallow water

Turbulant flow is when water particles collide and change direction to create eddies and a high velocity

Deposition is the laying down of solid material in the form of sediment on the bed of a river, it occurs when the river enters a lake or sea, when there is a sudden increase in river loads, shallow water or a flooded river

10 of 15

Downstream variation in Rivers

erosion takes place downstream where the river is deeper and has more discharge, sediment load decrease upstream and increase downstream, grain size increases upstream due to attrition and decrease downstream due to abrasion, the channel gradient decreases in the upper course of the river, the channel width decreases upstream and increase downstream due to increase in discharge, river velocity and river discharge is smaller upstream due to less energy and less friction, the channel bed is rougher upstream, the higher the hydraulic radius the more efficient the river is.

As a river flows from the source to the mouth it is narrow and unever due to boulders in the upper course, in the middle course the river meanders and the channel become assymetric, in the lower course the river widens and deepends further into a braided channel.

Potholes are circular depressions in the river bed, pebbles that are trapped in the hollows are swirled around by the water through Abrasion.

11 of 15

Rapids are a series of short and fast falls of flowing water in an area of reistant and less resistant rock. Occur when the water becomes shallow and the rocks are exposed above the surface.

WATERFALLS!

Meanders are a sinuous bend in the river, erosion occurs on the outside of the river and deposition occurs on the inside of the river.

Oxbow Lakes are horse shoe shaped lakes seperated from an adjacent river. Erosion occurs on the outerbanks and depositoin occurs on the inner banks which causes the meander to become thinner

Levees occur in the middle and lower course of a river, when a river floods the velocity of the water falls as it overflows the bank along the side of channel

Floodplains are created as a result of erosion and deposition, it is relatively flat areas of land either side of the river.

12 of 15

Delta is a feature of deposition, located at the mouth of the river.

Knickpoint usually marked by rapids and they represent rejuvenation as it is a sudden break in the long profile of the river.

Waterfalls the river falls over a rock edge in a deep plunge pool, retreat of the waterfall causes the gorge to retreat and uncutting occurs of the weak rock leaving the resistant rock

River terraces are narrow flat pieces of ground that run parallel to the river on either side

Incised Meanders caused by rejuvenation, steep cliff like bank

Rejuvenation is an increase in the energy of a river caused by either a fall in base level or uplift of the land

13 of 15

Cumbria, 12 inches of rain fell in 24hrs highest ever recorded, met office predicted heavy rain, saturated ground, low temperatures, low evapotranspiration, cockermouth and workington.
12 flood warnings, 100 million pound worth of damage, schools closed, 18 bridges destroyed, north side bridge collapsed - death of PC Bill Barker, chemist and shops demolished.
5 helicopters, water boats, emergency shelter in cockermouth school, 90 mile round trip, 8ft deep water, 200 people stranded, 12 months to mix

Bangladesh, monsoon(heavy rain), tropical cyclone brought strong winds, no slopes for surface runoff, rivers eroded levees which collapsed, shallow river channels, deforestation reduced infiltration and interception, soil erosion reduced river capacity, rise in sea level, high death rate, water borne diseases, limited chance to migrate, damage to crops, livestock death, loss of land, homelessness, stress, famine, increased community spirit, 10,000 volunteers produce warning to help with evacuation, broadcasts over loud speakers, cyclone shelters built

14 of 15

Hard Engineering =
-
dams building, 3 gorges dam china, reduces risk of flooding as it holds back water
- channel straightening, river line Cumbria
- levee building, mississippi, increase capacity of river and reduce chance of flooding
- diversion spillway, jubilee river, diverts excess water creating a completely new river

Soft Engineering =
-
forecasts, met office pass warnings onto environmental agency
- warnings
- land use management on the flood plain, controlled flooding to lower level of water in the river
- wetland conservation, plants and trees in the river slow the erosion down
- river restoration, restores small parts of the river

15 of 15

Comments

No comments have yet been made

Similar Geography resources:

See all Geography resources »See all Rivers and fluvial processes resources »