Glossary for Water on the Land Flashcards
Source
Where a river begins
Mouth
Where a river enters the sea (may be an estuary or a delta)
Tributaries
Smaller riers that join a larger river channel
Confluence
Where a tributary joins a larger river channel
Drainage basin
The area of land drained by a single river system
Watershed
The edge of the drainage basin (usually a high ridge of land)
Long profile
The entire length of the river from source to mouth
Cross profile
A cut-through or cross-section of the river at any one point. In the upper course the cross profile is a steep side v shaped valley, with a small narrow river. In the middle course it is less steep sided, with a wider floodplain and a wider river channel. In the lower course the cross profile is a very flat floodplain with a very wide river channel.
Discharge
The volume of water being carried in the river channel (measure in cumecs - m3/s
Erosion
The breakdown of rock and sediment by moving forces
Vertical erosion
The downward erosion of the river channel caused by the downward pull of gravity on the river water. This occurs in the upper course and creates a steep sided cross profile.
Lateral erosion
The sideways erosion of the river channel. This occurs in the middle and lower course and creates a very wide, flat cross profile.
Abraision
The river’s flow throws sand and sediment against the river bed and banks
Hydraulic action
The river’s flow erodes the bed and banks
Attrition
Particles carried in the river rub against each other and are worn down
Corrosion
The action of acids and salts in the river water corroding the bed and banks
Transportation
The movement of sediment from one place to another
Traction
The rolling of larger boulders on the river bed
Saltation
The bouncing of smaller boulders on the river bed
Suspension
When sediment is carried in the body of water
Solution
When sediment is dissolved in the water
Deposition
The dumping of the sediment load carried in the waves. Encouraged by a reduction in flow, a fall in discharge or an obstruction in flow.
Bedload
The sediment that is too large to be carried in the water and is found on the river bed (moved by traction and saltation at times of high flow).
Angular bedload
The bedload that is still very jagged - has not been smoothed via erosion (found in the upper course).
Suspended load
The sediment that is carried in the water (moved by suspension and solution).
Landforms of erosion
Landforms created by the erosive power of the river (eg V shaped valleys, interlocking spurs, waterfalls, gorges). Usually found in the upper course of the river.
V shaped valley
Vertical erosion in the supper course creates these steep sided, narrow valleys. The river cuts down, and weathering and mass movement work on the valley sides. Over time steep sides form.
Interlocking spurs
Areas of hard, resistant rock that the river flows around - found in the upper course (not to be confused with meanders which are found in the flat lower course).
Waterfall
A steep drop in the river’s course. Formed where a band of resistant rock overlays a band of less resistant rock. The softer rock is eroded by more, causing the undercutting of the harder rock. Abrasion and hydraulic power create a plunge pool, which over time undermines the harder rock. The hard cap rock eventually collapses and the waterfalls retreats back forming a gorge.
Gorge
A retreating waterfall creates a steep sided gorge - a extremely steep sided cutting.
Landforms of erosion and deposition
Landforms created by erosion and deposition (e.g. meanders and oxbow lakes). Usually found in the middle to lower course of the river.
Meander
Bends in the river’s course. On the outside of the meander bend the water is deeper and the current flows faster (higher velocity). The force of the water erodes and creates a river cliff. On the inside of the bend the water is shallower and flows slower, which encourages deposition. Sediment is deposited which creates a slip-off slope. An underwater current spirals down the river and carries the eroded material from the river cliff to the slip-off slope (known as helicodial flow).
River cliff
A steep cliff, found on the outside of a meander and created by erosion (abrasion and hyraulic power).