Rivers, floods and management 14

Read carefully the definitions below and choose the correct one.

Avulsions are the sudden change in the course of a river leading to a section of abandoned channel, a section of new channel, and a segment of higher land (part of the floodplain) between them.

Alluvial channels form in sediment that has been, and is being, transported by flowing water.They are very diverse owing to the variability in the predominant grain size of the alluvium, which ranges from clay to boulders

Meandering channels wander snake-like across a floodplain. The dividing line between straight and meandering is arbitrarily defined by a sinuosity of 1.5, calculated by dividing the channel length by the valley length.

Rivers, floods and management 15

Read the definition below carefully and write down the missing term.

___________ is a measure of how frequently streams occur on the land surface. It reflects a balance between erosive forces and the resistance of the ground surface, and is therefore related closely to climate, lithology, and vegetation. _____________can range from less than 5 km/km2 when slopes are gentle, rainfall low, and bedrock permeable (e.g. sandstones), to much larger values of more than 500 km/km2 in upland areas where rocks are impermeable, slopes are steep, and rainfall totals are high. Climate is important in basins of very high ____________ in some semi-arid environments that seem to result from the prevalence of surface runoff and the relative ease with which new channels are created.

Drainage density is a measure of how frequently streams occur on the land surface. It reflects a balance between erosive forces and the resistance of the ground surface, and is therefore related closely to climate, lithology, and vegetation. Drainage densities can range from less than 5 km/km2 when slopes are gentle, rainfall low, and bedrock permeable (e.g. sandstones), to much larger values of more than 500 km/km2 in upland areas where rocks are impermeable, slopes are steep, and rainfall totals are high. Climate is important in basins of very high drainage densities in some semi-arid environments that seem to result from the prevalence of surface runoff and the relative ease with which new channels are created.

Karst landscapes and processes 1

Match the figure below to the type of doline

Solution dolines start where solution is concentrated around a favourable point such as joint intersections. The solution lowers the bedrock surface, this way eating out a small depression.

Rivers, floods and management 1

Write down the missed process of the hydrological cycle: Interception, Infiltration, Precipitation

Water lost from vegetation via both evaporation and transpiration.

Rivers, floods and management 2

Choose the right definition of the term "Throughflow"

Water flows through the hydrological cycle in various ways:

Throughflow: where water moves downwards through layers of soil.

Channel flow: downhill movement of water in rivers.

Groundwater flow: Lateral movement of water from the water table.

Rivers, floods and managment 3

The water balance can be shown using the formula: P=Q+E +/- S

Write down, what is "Q" in that formula?

precipitation (P) = streamflow (Q) + evapotranspiration (E) +/- changes in storage (S)

Rivers, floods and managment 4

Choose the main processes of transportation of material in a river:

Transportation of material in a river begins when friction is overcome. Material that has been loosened by erosion may be then transported along the river. There are four main processes of transportation. These are:

  1. suspension / suspended load;
  2. solution / solution load;
  3. saltation; and
  4. traction.
Rivers, floods and managment 5

Choose the right type of energy that drives the hydrological cycle

Solar power
Rivers, floods and management 6

In which kind of graph could be studied the water balance of particular location?

A water budget reflects the relationship between input and output of water through a region. The water balance graph shows precipitation and potential evapotranspiration both as line graphs. Thus we have a direct comparison of supply of water and the natural demand for water. It is possible to identify the periods when there is plenty of precipitation and when there is not enough.

Rivers, floods and management 7

Choose  true or false: Urbanisation and deforestation have simular effect on storm hydrograph?

A hydrograph or storm hydrograph is a type of graph that shows how a rivers' discharge responds to a period of precipitation. Discharge is measured in one point (using the units cumecs), but precipitation is measured over the whole drainage basin. On the hydrograph, precipitation is shown using a bar graph and discharge is shown using a line graph.

Deforestation and Reforestation: If a drainage basin has been deforested, then there will be less interception. Precipitation will fall directly on the ground. This will increase the speed that the ground becomes saturated and also increase surface run-off. This will reduce the response time and lag time. If any area is forested or been reforested then there will be more interception, root uptake and transpiration. These three factors will reduce the peak discharge as well as slowing the lag time.

Urbanisation: Settlement building can have varying effects. Urban areas usually result in deforestation and an increase in impermeable surfaces. This can increase surface run-off and reduce lag time and increase peak discharge. Urbanisation can, however, increase interception with the large number of buildings - this will slow the lag time. Artificial drains may control the flow of water or increase the flow of water into rivers.
 

Rivers, floods and management 8

Write down to which type of river process does belong hydralic action?

Hydraulic action

The pressure of water breaks away rock particles from the river bed and banks. The force of the water hits river banks, and then pushes water into cracks. Air becomes compressed, pressure increases and the riverbank may, in time collapse. Where velocity is high  e.g. the outer bend of meaner, hydraulic action can remove material from the banks which may lead to undercutting and and river bank collapse. Near waterfalls and and rapids, the force may be strong enough to work on lines of weakness in joints and bedding planes until they are eroded.

Rivers, floods and management 9

Name the basin in the botton of a waterfall

Rivers, floods and management 10

Choose the type of enviroment/location in which do braided channels occur

Braided channels occurs in rivers with high slope when, threshold level of sediment load or slope is reached, any slope over this threshold creates a braided stream. This occurs due to rapid evaporation and infiltration after period of heavy rainfall, it can lead to deposition of sediment load. Braiding is caused by fluctuations in discharge levels, low river velocity and also by the stream or river losing.Capacity- optimum load which can be carried.Competence- the maximum size or weight of the load which can be carried.Braided streams occur in areas where the transported load contains ahigh amount of coarse material such as sands and stones

Occurs in glacial outwash plain and semi-arid areas.

Rivers, floods and management 11

Choose 3 landforms that occur due rejuvanation:

Rejuvenation occurs when the river’s base level falls (i.e. when sea level falls). This can be a consequence of either a fall in the amount of sea water or the land rising. Both are the result of the comings and goings of ice ages. The effect on rivers is to produce features called “knick points” (which can be seen as waterfalls and rapids), river terraces and incised meanders.

Rivers, floods and management 12

Choose 3 economic impacts of flooding

Impacts of flooding:

  1. loss of standing crops.
  2. drinking water will be difficult to get.
  3. electricity supply will be cut off.
  4. loss of life.
  5. loss of live stocks.
  6. loss of wild life.
  7. moving from place to place will be very difficult.
  8. government has to make arrangement for shelter and food for large population
  9. to restart normal life government has to give monetary and material aid.
  10. because of heavy flooding cultivation and farming of land requires lot of efforts and money..
  11. houses will be damaged ,
  12. schooling and education of children will be affected.
  13. road transport will be cut off.
  14. because of stagnant water, mosquitoes will increase,and disease will spread quickly.
Rivers, floods and management 13

Choose 3 landforms of deposition

Cave, bay and cliff are examples of landforms of erosion