Riparian Environments

The Hydrological Cycle
The Hydrological Cycle is a closed system, where water is continuously cycled between the oceans, the land, and the atmosphere in a series of processes known as the global hydrological cycle.

Water moves through the hydrological cycle via a series of flows or transfers. Water is also stored within the system, for example, in a lake.

Below is a diagram to show the hydrological cycle:


**Student Quiz Round**
Can you match the components to their meanings?

1) _______: water soaking into the soil from the surface.
2) _______: water moving within rocks below the ground.
3) _______: water moving downhill through the soil layers. It will generally move slowly, but flow may concentrate along the lines of roots or soil weaknesses and form natural pipes; the flow in these will be much faster.
4) _______: water deposited on the ground as a liquid or as a solid, for example rain, hail, snow, or even fog.
5) _______: water moving downhill with rivers.
6) _______: water moving across the surface of the ground. This my happen when the rain cannot soak quickly enough into the ground, for example whre there are tarmac surfaces or hard-baked soil, or even during heavy rainfall. Saturated overland flow is more common and occurs when the soil is saturated and infilration cannot take place.
7) _______: the combined processes of evaporaton and transpiration that result in the loss of water from the leaf. Transpiration is the loss of water through tiny holes called stomata in the leaf surface. In practice it is very difficult to calculate the two amounts seperately, so they are often grouped together.
8) _______: plants trap some of the precipitation so it may not immediately pass to the ground. Some may drip to the ground as throughfall; some may flow down the stem as stemflow. Alternatively, the precipitation may evaporate directly off the leaf and never reach the ground.
9) _______: water moving from the surface layers of soil into deeper layers of soil and rock.
10) ______: water changing from its liquid form to a gas (water vapour) and returning to the atmosphere.

**Channel Flow, Evaporation, Evapotranspiration, Groundwater Flow, Infiltration, Interception, Overland/Surface Flow, Percolation, Precipitation, Throughflow**

The drainage basin as part of the hydrological system


A drainage basin is an area of the land's surface from which a river receives its supply of water. The edge of a drainage system can be marked by an imaginary line called the watershed. The watershed is usually marked by areas of higher land.











Drainage Basin System
Unlike the hydrological system, the drainage basin works as an open system requiring inputs from outside in order to function. Below is a diagram of the drainage basin system:

Drainage basins have many different characteristics that influence how quickly or slowly the main river within them responds to a period of intense rainfall. More information is explained in the following section about storm hydrographs.

Storm Hydrographs
The dischatrge of a river at any point can be plotted on a hydrograph. A storm, or flood, hydrograph shows the river's response to a single rainfall event. An annual hydrograph indicates the yearly pattern of flow. Both types of hydrograph are useful tools as they allow us to study drainage basin processes and river channel response.

The main features of a storm hydrograph can be viewed in the figure below:


http://www.s-cool.co.uk/alevel/geography/river-profiles/storm-hydrographs-and-river-discharge.html#reading-the-hydrograph

Coasts: Transport and Deposition

Transport and deposition
Waves approaching at right angles to the coast move material up the beach if the waves are constructive. Constructive waves have a long wavelength but low height. Destructive waves are closer together and higher. As they plunge on the beach they comb down material and flatten the beach gradient.

Waves breaking on a beach at an oblique angle move sand and shingle by the process of longshore drift. The breaking wave (the swash) moves material up the beach at an angle whilst returning water (backwash) moves the material back at right angles to the beach. The net effect is a longshore movement.

Offshore, the build up of water against the coastline creates a current parallel to the shore. Whilst it can only move sand-sized sediments, it is capable of moving tens of thousands of tonnes of sand per year.

Coastal Processes and Landforms

Erosion at the coast
This section will go into greater depth about the processes affecting coastal environments, and what landforms occur because of it. First, I'll look at erosion at the coast.

Erosion can be seen in action on cliff coastlines. It is most rapid on soft rock coastlines. The processes responsible for cliff erosion can be classified into two types:

*Those active at base of cliff (cliff-foot or marine processes, including hydraulic action, corrasion and attrition

*Those active on the cliff face (sub-aerial processes, involving the action of weathering

The patterns of erosion are influenced by a wide range of factors including:

*rock type- its resistance to wave action, its resistance to sub-aerial processes (landslides, gulleying), and its solubility.

*rock structure- the way the rock is divided by joints, bedding planes, and faults. Erosion takes place in joints, cracks and bedding planes.

*beach character- a wide beach may be protective and halt erosion even on weak cliffs. The size of the beach may vary with the seasons. The beach may shrink if erosion and sediment supply is reduced 'updrift' by sea walls or groynes. Offshore dredging may remove beach material from the coast zone.

Hydraulic Action
This is the action of breaking waves on cliffs. A storm may throw hundreds of tonnes of water against a cliff face with every breaker. The shock of the impact can loosen rocks and air trapped in joints and faults can blast the rock with extreme pressure.


Corrasion
This is the process by which pebbles and sand forced against cliffs succeed in wearing away new rock. Corrasion (sometimes referred to as abrasion) produces wave-cut notches under cliffs and, eventually, wave-cut platforms. For corrasion to continue, attrition must be effective.

Attrition
This is the process by which erosion continues to operate by grinding down cliff fall material. After hydraulic action and corrasion have eroded cliffs,the eroded material lies at the base of the cliff, forming a protective armour which is often too large for the sea to move. By grinding smaller particles against these large block, the size is eventually reduced until the sea can move them away.


Solution can also cause coastal erosion as acids in the water dissolve rock particles and minerals.

Coastal Environments: An Introduction

Coasts- an introduction.
The coast is that unique, valuable, and often threatened area where the sea meets the land. The coastline is an ever-changing boundary zone between the habitable terrestrial environment and the inhospitable marine environment. Coasts are valued in many ways as they are:

*premium economic sites for industry and marine trade

*rich and diverse habitats and ecosystems

*highly valued sites of tourism and recreation

*a natural form of coastal protection (wide, gently sloping beaches)

*sites of dense residential development

There is considerable competition for land and sea resources by various groups, often resulting in severe conflicts. Coasts form geomorphologically active landscapes, undergoing constant change.

Coastal Systems
It is important to realise that coasts are dynamic and places of constant change. The changes are the result of four independent controlling influences, and they are listed below:

*Global tectonics- can operate over a very long period of time

*Relative land-sea changes- can operate over a very long period of time

*Intervention by humans (short-term of rapid impact)- i.e. sea defences, port development, recreation, industrial or residential development.

*Natural processes of coastal erosion and deposition- accretion.

It is the latter that will be mentioned first in this blog.

Short-term natural processes
This section will focus on the short-term natural processs, and explore how waves, tides, winds and mass movement processes can change the form of coasts. This section will be broken down into a further three sub-sections.

What are the energy and sediment inputs into the coastal system?

Source of coastal sediment- The narrow zone between high and low water (the littoral zone) is a place where energy and sediment concentrate. The energy sources include wind, waves, and tidal currents. The sediments on the coast include sand, shingle and clay. Under natural conditions, there is always a balance between the energy levels and the sediment movements so that erosion taking place in one location is balanced by deposition taking place somewhere else.

Rivers bring sediment from the land to the coast. Usually fine grained silts, clays and sands. This can result in salt-marshes and deltas. Erosion of cliffs by the sea produces large amounts of material for beach building. Usually coarse sand and shingle is produced. The sea is an important source of sediments. Huge volumes of sand and clay were deposited here in the ice age. Tides and waves may bring these shorewards to build offshore bars or add to beaches.

Sources of coastal energy
There are three main energy sources at work in the coastal zone: the wind, waves and currents.

The Wind- The wind can be very effective at moving sand inland to produce sand dunes, particularly on beaches with shallow, offshore gradients and a large supply of sandy sediment. These often produce important ecosystems, such as Oxwich Bay in South Wales, and the Studland dunes of Dorset.

A picture to show dunes that have been formed at Saunton Sands, North Devon.

Waves
The power of waves depends on the wave height. A smallincrease in wave height produces a large increase in wave energy. The wave height depends on the speed of the wind, and the length of time the wind has been blowing over the sea. This depends on the distance- or fetch. In Britain, the maximum fetch is west and south-west over the Atlantic.

Tidal Currents
Incoming (flood) and outgoing (ebb) tidal current can move fine-grained sand and silts. Tidal currents are most powerful where the tide range is high and the coastline is a funnel shape.

An Introduction

Hello!

My name is Christian Capell, and this year I have completed a BSc Degree in Geography and Planning at the University of Birmingham. In September, I will start my PGCE in Secondary Geography at the University of Leicester. In preparation for this, I have created a blogspot to demonstrate development in my subject knowledge. As I have particularly focused on Human Geography in my Degree, I feel it is necessary to focus on Physical Geography. From now until the start of the PGCE, this blog will blossom into a site of useful resources and information relating to Geography. I hope you enjoy visiting my blog!