geo
·Corrasion – Wearing away of the river bed and banks by the load hitting against them.
·Attrition – Wearing down of the load as the rocks and pebbles hit the river bed and each other.
·Hydraulic Action – Breaking away of river bed and banks by the sheer force of the water getting into small cracks.
·Chemical Action (Corrosion) – Water dissolves minerals from the rocks and washes them away.
·Traction – Quite large stones can be rolled or dragged along the river bed by the force of the water.
·Saltation – Small stones which the water cannot lift bounce off each other and are carried forward by the water above the river bed for short distances.
·Suspension – If particles are small enough the river can lift them and carry them long distances.
·Solution – When the river dissolves minerals from the rocks they are carried in the water itself.
·Loss of Speed – When the river slows down on the inside of bends or when it meets deeper water, like a lake, it loses energy and cannot carry so much, so drops some of its load.
·Load – All the materials moved by the river by traction, saltation, suspension and in solution.
·Alluvium – The sands, silts and mud left by the river in its valley. This often forms a fertile soil.
·Estuary – The wide mouth of the river where it meets the sea.
·Delta – A river mouth clogged by deposits where the stream breaks up into smaller and smaller branches before reaching the open sea.
The river is meandering across the valley
The river is eroding laterally (from side to side)
The river erodes the outside of the bends and deposits on the inside so its course is changing
This erosion narrows the neck of the meander
Often during a flood, the river will cut through the neck
The river continues in the new bed and the meander is abandoned
New deposition seals off the ends and the cut-off becomes an ox-bow lake
The characteristics of the source to the mouth including discharge, depth, velocity, width, bedload size and roundness, and the gradient. Velocity increases with the distance downstream. There’s less contact between bed and bank thus reducing energy lost to friction and erosion occurs, which increases channel depth, width (cross-section area) and wetted perimeter as there’s more water added. The discharge increases as velocity and cross-section area increases. As the distance downstream increases, the bedload quantity will increase as the velocity increases, the river has more energy and is thus capable of carrying more load. Bedload size decreases and becomes rounder as the distance downstream increases because higher velocity gives greater erosion. The gradient decreases as the river flows and the width and depth increases. Gravity and river meander also causes the water travel downhill and not following a straight path.
1.16m
2.250cm
3.positive correlation, as depth increases, velocity increases due to less contact between bed and bank thus reducing energy lost to friction and erosion occurs. There are two anomalies: 11m and 17m due to the high lake level, which more water is added into the river.
4.Positive correlation, as the velocity increases, bedload size increases due to the increase in velocity, the river flows faster, which give more power for erosion and this transports away and pick up bigger rocks. The anomalies are the same for a)
5.Cross-sectional area (width x depth) multiply by mean velocity (m/sec). Discharge is shown as cumecs
A river has its own source, which is usually an upland area where a river starts, and its own mouth which where a river flows into a sea or lake. River’s attributions change from upstream (source) and downstream (mouth). As the river flows towards the mouth, the slopes become less steep. Eventually the river will flow over flat land as it approaches the sea. The characteristics of the source to the mouth including discharge, depth, velocity, width, bedload size and roundness, and the gradient. As more water joins the river from the tributaries and the surrounding drainage basin, there is more energy, which causes more erosion. This causes increase in velocity and cross-sectional area. Discharge will increase as a result of water entering the river via surface runoff, overland flow, through flow and groundwater flow. The velocity increases as more water is added into the river through tributaries, following deeper and wider channel due to more erosion energy and friction, therefore, water flows faster and increase the velocity. Shape of the channel also refers to its cross section (width x depth). The wetted perimeter is the extent to which water is in contact with its channel.
The greater the wetted perimeter, the greater the friction between the water and the banks and the bed of the channel and this will slower the flow of the river. (the narrow channel will have faster flow of river compared to wider channel will flow slowly) Also, as the gradient increases with distance downstream, steep gradient has fast velocity, gentle gradient has slow velocity, all of this are due to the force of gravitational force and river changes from eroding vertically at the source, to laterally further downstream, pulling the speed of the river flowing. Stone size decreases downstream and the stones get rounder and smoother as rivers erode the rocks progressively as the stones are transported downstream. The processes of river erosion operate here. Load quantity is also variable, capacity is a measure of the total amount of load that a river can carry, whilst the competence is the biggest size of load the river can transport. These characteristics can change due human interference, such as water extraction, farmland, fish farming and local river management.