Higher Hydrosphere

This occurs where the river looses the surplus energy it requires to transport material and it is deposited.&nbsp;This can occur due to: •Rivers reach a sea or loch •Rivers overflow their banks •On the inside of a river bend •Flood water subsiding or drought •Sudden decrease in gradient (plunge pool) When this happens the river will deposit the heaviest material first and transport lighter material (load) further.&nbsp;In this way the load is sorted by weight.

Study Diagram For the River Valency at Boscastle on 16 August 2004: (a) describe the changes in discharge level and (b) suggest reasons why these changes may have occurred. 10

Describe the movement of water within a drainage system. 6

The river is meandering across the valley, in the lower course (1). The river is transporting material by suspension and therefore eroding laterally (1). The river flows faster on the outside bends (1) and creates an incised meander (1). Continual erosion narrows the neck of the meander (1). Often during a flood the river will cut through the neck (1) and take the shorter course (1). The river continues on its straighter path and the meander is abandoned (1).

Fastest flow now in centre of river and deposition occurs on the bank cutting off meander (1). Meander is blocked off creating an ox-bow lake, this will eventually dry up (1)

The amount of surface streams in the river basin.&nbsp;Density is highest on impermeable rocks &amp; clays, therefore a shorter and higher lag time.

HYDROSPHERE Higher Geography

b) Explanations may include: 1. Basin Size: it may be a small catchment area meaning less travel time to the main channel (1 mark) 2. Relief: the catchment area may be steep leading to rapid overland flow to the channel (1 mark) 3. Stream Density there may be a high number of tributaries transporting water to the channel quickly (1 mark) 4. Land Use this rain may have been intercepted by vegetation (1 mark) the water may also have infiltrated and be stored in the soil (1 mark) the river rises because soil storage has been exceeded (1 mark) 5. Rock Type the river may rise because of impermeable surfaces leading to rapid surface run-off (2 marks)

Rainfall in a small basin will reach the main river channel more rapidly, Lag time will be shorter.

1. Formation of erosional and depositional features in river landscapes: — V shaped valley — waterfall — meander — oxbow lake 2. Hydrological cycle within a drainage basin 3.&nbsp;Interpretation of hydrographs

Harder rock is overlying softer rock (1), allowing differential erosion takes places (1). The softer rock is more easily eroded (1) this causes undercutting and an overhang of harder rock (1), eventually there is nothing to support the harder rock which collapses (1) due to gravity into the plunge pool(1). This process is repeated causing the waterfall to gradually retreat upstream (1).&nbsp;

<a href="https://www.twigscotland.com/film/waterfalls-and-gorges-1777/">https://www.twigscotland.com/film/waterfalls-and-gorges-1777/</a> 3.08 minutes

Feature 3. Meander

Impermeable rocks (e.g. Granite) do not allow water to pass through and so increase overland flow.&nbsp; Permeable rocks allow water to pass through so reduce overland flow.

Valleys in the upper course are steep sided (1). The river transports its load by Traction when stones are rolled along the riverbed (1), and by Saltation when pebbles are bounced along the riverbed (1) in this way the river is eroded downwards or vertically (1). The sides of the valley are affected by the rain and gravity causing more material to fall into the river (1). The valley bottom is usually narrow and filled mainly by the channel (1).

<a href="https://www.bbc.co.uk/bitesize/clips/zw8pyrd">https://www.bbc.co.uk/bitesize/clips/zw8pyrd</a> 0.40 minutes

Explain the formation of an ox-bow lake. You may wish to use an annotated diagram or diagrams. 10

Physical &amp; Human factors affecting Hydrographs

There are several factors that can affect how the hydrograph looks. Obviously, the amount and duration of the rainfall is the biggest factor but there are 5 other things we need to consider.

Feature 4. Ox-Bow Lake

3.&nbsp;Interpretation of Hydrographs

Hydraulic action which is when air is compressed into the riverbank (1) causing materials to be dislodged (1) Abrasion when the force of the water (1) throws bedload against the banks causing erosion (1) Attrition when rocks &amp; boulders collide and break up (1) these smaller pieces can aid with abrasion (1).

Solution when the river water dissolves minerals from the rocks (1) and washes them away (1).&nbsp;

<a href="https://timeforgeography.co.uk/videos_list/rivers/river-erosion-processes/">https://timeforgeography.co.uk/videos_list/rivers/river-erosion-processes/</a> 6.08 minutes

Explain the formation of a waterfall. You may wish to use an annotated diagram or diagrams. 8

River Basin / River Catchment

<a href="https://www.bbc.co.uk/bitesize/clips/z4n9wmn">https://www.bbc.co.uk/bitesize/clips/z4n9wmn</a> 1.09 minutes

Steep slopes of the basin and valley sides will allow water to get to the channel quicker, so a shorter lag time.

Traction&nbsp;- quite large stones can be rolled or dragged along the riverbed by the force of the water. Saltation&nbsp;- small stones which the water cannot lift, bounce off each other and are carried forward for short distances by the water above the riverbed. Suspension&nbsp;- 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.

<a href="https://timeforgeography.co.uk/videos_list/rivers/river-transport-processes/">https://timeforgeography.co.uk/videos_list/rivers/river-transport-processes/</a> 4.49 minutes

a) Descriptions may include: there is a lag time of five hours (1 mark) there is a slow rise in discharge until 09:00 (1 mark) there is a steep rising limb (1 mark) leading to a peak discharge of 100 cumecs at 18:00 (1 mark) the rising limb becomes less steep briefly between 13:00 and 15:00 (1 mark) there is a steep recession limb from 18:00 until 22:00. (1 mark) b) Explanations linked to rainfall may include: this is caused by the initial rainfall which began at 07:00 (1 mark) the steep recession limb is due to there being no further rain after 15:00. (1 mark)

Vegetation reduces and slows the overland flow due to interception from branches and roots. Less during the winter when deciduous trees have shed their leaves. Trees reduce and slow more water than grassland or crops. &nbsp; Urbanisation can increase and speed up overland flow due to tarmac streets, gutters and drains.

1. Formation of erosional and depositional features in river landscapes:

A typical river process can be split into 3 sections, Upper, Middle &amp; Lower courses. As the river flows downstream much of the energy is used up overcoming friction from the riverbed &amp; banks. Energy comes from the volume &amp; velocity (speed) of the river.&nbsp;

Physical Factors affecting The Drainage Basin

Storage &amp;Transfer Interception – Water held by vegetation Surface Storage – Water held on the surface of the ground Overland flow – Water flows away by streams and rivers or overland by sheet wash due to heavy rain, due to gravity. Infiltration – Water flows down into the soil Soil Storage – Water is held in the soil, how much water can infiltrate and by stored by the soil depends on how porous the soil is.&nbsp;Large pores within the soil allow water to flow through it easily, e.g. Sand.&nbsp;Smaller pores within the soil allow less easy infiltration leading to more surface storage, e.g. clay. Through Flow – Water flows away through the soil, due to gravity. Percolation – Water flows down into the rocks, how much water can percolate will depend on the type of rock and how permeable it is. Impermeable rock leads to more soil storage. Groundwater Storage – Water held in rock which makes up the water table. Groundwater Flow – Water flows away very slowly to rivers and streams.

Riffles and pools lead to changes in speed and depths in the river channel (1) River flows fastest on the outside bend (1) increasing the erosive power (1) River flows slowest on the inside bend leading to deposition (1)

Helicoidal flow moves materials across the river channel. (1) This leads to river cliffs and beaches developing (1) Meanders migrate downstream as erosion continues. (1)

<a href="https://www.twigscotland.com/film/meanders-and-oxbow-lakes-1778/">https://www.twigscotland.com/film/meanders-and-oxbow-lakes-1778/</a> 3.28 minutes

Inputs Precipitation –The type, intensity, duration, frequency &amp; amount of precipitation. Outputs Evapotranspiration – Amount and type of vegetation and surface storage (ponds / lakes etc)&nbsp; Drainage Basin – Amount of streams / burns and rivers in the system.&nbsp;

Features: 1.V-Shaped Valley 2.Waterfall

2. Hydrological cycle within a drainage basin

<a href="https://www.twigscotland.com/film/how-are-rivers-formed-1121/ ">https://www.twigscotland.com/film/how-are-rivers-formed-1121/</a> 3.11 minutes

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