• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Hydrology and Fluvial geomorphology. (Q&A)

Extracts from this document...

Introduction

HYDROLOGY AND FLUVIAL GEOMORPHOLOGY Q: "Human activity, climate and landscape all affect a rivers regime". Discuss with reference to rivers from around the world. Suggested Answer The river regime is the expected seasonal pattern of discharge at a given point, over a year. The discharge is the amount of water flowing in the river channel. It is calculated by multiplying the cross-sectional area by the mean velocity (speed). A river's regime is based on average monthly discharge figures. These are collected over at least 20 years to try to eliminate minor year-to-year variations. There are several factors which will affect the river's regime, including rainfall, temperature, human use of the land and the landscape. For a better answer it is suggested that each of the factors has to be explained with examples using named rivers how each one may affect the regime of the river. Factors affect the regime Human activity means 'how people use the river and the surrounding land'. For example, if vast amounts of water are taken out of the river by industry, this may affect the regime as it will artificially decrease the amount of water in the river (although most industries do return the 'used' water to the river channel). In a similar way, if large amounts of water are used for agricultural irrigation, or water is removed from the river and directed somewhere else, the amount of water flowing past the measuring point will decrease. It also needs to consider the possible impact on a river of increased urbanisation i.e. increased surface run-off and the water reaching the river more rapidly. Climate can be divided into temperature and rainfall, as both of these will affect the river's regime. The river regime may be linked to the pattern of rainfall, for example, there is a higher river discharge when there is more rainfall and vice versa. On the other hand, if most of the precipitation falls as snow and is held in storage over the winter months, the discharge will be lower then and will increase dramatically during spring when the snow thaws. ...read more.

Middle

These factors will all affect the field capacity of the soil and so the amount of surface water it can absorb. The quantity of water already present in the pore spaces before a rainstorm will directly affect the ability of the soil to absorb more from the surface. This antecedent moisture (water which is already present) will therefore influence overland flow rates. If the soil is already saturated with water, overland flow will be rapid and greater in volume than if there is plenty of capacity available in the soil store. The timing of the last rainfall to take place, its intensity and amount will be important factors in determining the capacity for storing new inputs. The percolation rate will depend on the nature of the soil store and also directly on the permeability of underlying rock which is present. Therefore, when these soil and groundwater stores are full, or saturated, then water is transferred into the river channel, partly by overland flow. Some of the water input into the system is also transferred horizontally along the soil profile by throughflow into river channels. Finally, some water flows slowly at depth underground by groundwater flow (sometimes called baseflow). Smaller soil and groundwater stores will lead to increased overland flow rates overall because the ground will become saturated more quickly. Q: How does the amount and location of water change in a hydrological cycle? Suggested Answer The hydrological, or water cycle is a model used to explain the movement of water on the planet. The hydrological cycle is extremely complicated and the relationships between some parts of it are still poorly understood, although it is becoming clear that there are serious implications to humans' interference with its workings. The hydrological cycle is a closed system, which means that the total amount of water in the global system stays the same, or is conserved, overall. The total amount of water in the Earth's hydrological cycle can only be estimated: the US Geological Survey suggested the total water volume to be around 1,384,000km3. ...read more.

Conclusion

In a highland area, the channel tends to be rough in shape with rocks sticking out of the river bed. The load is angular and often consists of larger boulders and rocks. These all mean there in an increased wetted perimeter. This leads to greater friction. A lowland river, however, will have a wider channel and a much smaller load, meaning a reduction in friction, leading to an increase in the river's efficiency. Q: What are factors can be used to assess the flood risk in the global hydrological cycle? Suggested Answer The following are some of the factors, which you can expand on and give examples of: Rainfall and other precipitation Obviously the more rain the higher the flood risk, but the extent of the risk depends on what happens to the rainfall as below. Rate of runoff This is affected by angle of slope, soil and vegetation cover. Infiltration rate If most of the rainfall infiltrates into soil and permeable rock, this slows runoff into rivers. If infiltration is reduced by covering land with buildings, concrete and tarmac, water is rushed off into drains and reaches rivers quickly, causing flooding. Interception Vegetation, particularly trees, trap some rainfall as leaves get wet . If vegetation is removed, there is less interception, more runoff and more flooding. Evaporation During warmer seasons, evaporation (& transpiration) removes water before it can cause flooding. In cold seasons, with less evaporation (& transpiration), more water reaches rivers. Transpiration Vegetation, particularly trees, take up large amounts of rainfall through roots and give it off as transpiration. If vegetation is removed, there is less transpiration, more runoff and more flooding. Snow melting causes flooding if it happens quickly with a sudden rise in temperature. Silting of river channels makes drainage less efficient and can cause them to flood. Global warming causes a rise in sea level leading to flooding by sea and stopping the drainage of water from rainfall. It can increase rainfall and flooding in some areas of the world. The biggest risk of flooding is caused by combinations of the above factors. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Hydrology & Fluvial Geomorphology section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Hydrology & Fluvial Geomorphology essays

  1. Explain how human activity can modify the hydrological cycle.

    A lot of water reaches the river in a short time so the rising limb is steep, and the lag time is shorter so peak discharge is therefore higher, see Figure 2 Glaciers and ice caps melting may be due to global warming which is an indirect affect on the hydrological cycle by humans.

  2. An investigation into changes in channel parameters down the river Horner

    So I think that the river is wider and shallower at site three due to a change from vertical to lateral erosion and due to a possible harder rock type. This is the same explanation for why the pebble size is so great at site 3.

  1. 'How does the risk of flooding vary along the course of the River Eea?'

    At site two a lot has been done to reduce the risk of flooding, the farmers here are trying to protect their farmland so the river channel has been almost completely man made. Depending on the factors of flooding that you choose to look at, the risk of flooding will vary greatly.

  2. My hypotheses are:The character of the course of the River Bollin will change along ...

    When the water reaches a meander, the flow is faster on the outside of the bend, where it is slower, despoliation occurs, this forms beaches on the inside of the bend.

  1. How does the Efficiency and Cross-Sectional Area of a River Change Down Stream?

    By looking at the cross-sectional area I can see how large the river becomes further down stream; however in some areas like at site 4, there is a sudden change. This could be due to human impact changing the river shape.

  2. How does Loughton Brook change as it moves downstream?

    Again they show dramatic change in depth and shape of the cross section as we move downstream. This again shows the increase of the efficiency of the river. These 5 graphs can be related to the graphs of the Width so that as the width increases as we move further downstream.

  1. Geography investigation - The River Skirfare located in the Littondale region in the Yorkshire ...

    This is true for all the locations in the river (except 'Middle') and the average velocity also. The Middle reading shows that Halton Gill has the larger velocity though. This is most likely an anomaly, especially as the other locations would seem to support the theory that Arncliffe has a greater velocity than Halton Gill does.

  2. Investigating the river Caerfanell

    and place the pin of the pole on top the rock pointing up straight. - The person marked at 0m should then place the clinometer two-thirds up the pole at the colour change and aim at the exact same point on the other pole.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work