rivers COPY Flashcards
precipitation
Moisture falling from clouds as rain, snow, or hail.
Interception
Vegetation prevents water from reaching the ground
Surface Runoff
Water flowing over the surface of the land into rivers
Infiltration
Water absorbed into the soil from the ground.
Transpiration
Water lost through the leaves of plants.
Upper Course of a River
Near the source, the river flows over a steep gradient from the hill/mountains. This gives the river a lot of energy, so it will erode the riverbed vertically to form narrow valleys
Lower Course of a River
Near the river’s mouth, the river widens further and
becomes flatter. Material transported is deposited
physical causes of flooding
Long periods of rain causes soil to become saturated leading to runoff.
Steep-sided valleys channel water to flow quickly into rivers causing greater discharge.
Impermeable rocks cause surface runoff to increase river discharge.
human causes of flooding
Tarmac and concrete are impermeable. This prevents
infiltration & causes surface runoff.
Formation of a Waterfall
1) River flows over alternative types of rocks.
2) River erodes soft rock faster creating a step.
3) Further hydraulic action and abrasion form a plunge
pool beneath.
4) Hard rock above is undercut leaving cap rock which
collapses providing more material for erosion.
5) Waterfall retreats leaving steep-sided gorge.
Formation of Floodplains and levees
The river channels get shallower during low flow conditions, causing deposition on the river bed.
This means that the river cannot hold as much water as before as the river bed has risen.
During a flood, sediment is deposited on the river banks; depositing coarser (heavier) sediment nearer to the river and finer sediment further away.
River Discharge
River discharge is the volume of water that flows in a river.
Hydrographs that discharge at a certain point in a river changes over time in relation to rainfall
Peak discharge
the discharge in a period of time
. Lag time
the delay between peak rainfall and peak discharge
. Rising limb
the increase in river discharge.
Falling limb
the decrease in river discharge to normal level
Factors affecting hydrographs
Basin size – small flashy *Drainage density - high = flashy
rock type - impermeable = flashy *Land Use urbanisation = flashy *Relief - steep = flashy
Soil moisture – saturated = flashy * Rainfall Intensity –
high = flashy .
opposite characteristics & precipitation = SUBDUED
The River Tees location and background
Located in the North of England and flows 137km from the Pennines to the North Sea at Red Car.
Geomorphic Processes Upper
– Features include V-Shaped valleys, rapids, and waterfalls.
High force Waterfall located close to Forest-in Teesdale drops 21m
and is made from harder Whinstone and softer limestone rocks.
Gradually a gorge has been formed.
geomorphic processes middle
– Features include meanders and ox-bow lakes. The
meander near Yarm encloses the town.
geomorphic processes lower
– Greater lateral erosion creates features such as floodplains & levees near Darlington. Mudflats at the river’s estuary.
Middle Course of a River
Here the gradient gets gentler, so the water has less energy and moves more slowly.
The river will begin to erode laterally making the river wider.
Soft Engineering
Soft engineering involves adapting to natural hazards and working with nature to limit the damage. For example, planting trees to limit flood risk.
Hard Engineering
Building structures to deal with natural hazards, such as dams to prevent flooding