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

Flooding, one of the most disastrous natural hazards.

Extracts from this document...

Introduction

Geog Summer Assignment- Essay Question 2 Stella Kwok (7) Flooding is one of the most disastrous natural hazards. Take Huang He Basin in China as example, originally, intense rainfall in summer is one of the main causes of flood. With rapid urbanization and population growth, the built environment and the socio-economic characteristics is getting more important in contributing to flood hazards. To minimize the impact of flooding, take Huang He Basin in China as example, some preventive measures, such as flood control projects, are carried out. Flooding refers to the inundation by water of any land area not normally covered with water owing to a relatively rapid change of the water level. It often happens in the lower course of Huang He Basin. Firstly, physical environment is one of the main factors leading to flooding. Meteorologically, snowmelt in the upper course in spring causes sudden increase in discharge and blocking of ice-floes in river channels. In summer, the rainfall is concentrated in July and August, being highly variable. ...read more.

Middle

Runoff increases as a result of deforestation. This causes rapid concentration of discharge, reaching flood stage and peak discharge. Landslides are common, which dam river channels and block channel flow, causing the river to overflow its banks. Besides, the Huang He has dissected the loess plateau region in the middle course. Therefore it carries heavy sediment load to the lower course and flood plain. Hence there is heavy silting and deposition in the lower course and flood plain in river channels, raising the river channel floor and so water level along river banks during flood, hence building up leeves which may breach under great stress on the surrounding floodplain. Together with the perception of people in the region, who are ignorant of the likelihood of floods and their disastrous consequences and are prepared to take a calculated risk that the protective measures will save them from most floods. Yet the risks of flooding are under-estimated. Harmful effects could be disastrous. ...read more.

Conclusion

Area of arable land is increased because cultivation can be extended into marginal lands. Despite the economic benefits, some ecological problems are always resulted from the projects. To begin with, flood control and silt retention result in loss of annual addition of nutrients to the flood plains, so the nutrient status of soil is lowered. Secondly, sediments trapped behind dams cause silting of reservoirs, the aquatic ecosystems are upset. Thirdly, with increasing productivity, the use of fertilizer is widespread, thus causing stream pollution. Moreover, excess irrigation water raise the ground water table, causing water-logging and salinization of soil, this leads to changes in soil and in habitats. Not only are this, increase of irrigated fields causes increase in evaporation and relative humidity, microclimate is then changed. All in all, flooding can badly affect both the ecology and the economy of a country. Preventive and flood control measures can by no means be neglected. However, it seems that people are still more economic-conscious and at the same time ignoring the effects imposed on the ecological balance through the projects. ...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. 'How does the risk of flooding vary along the course of the River Eea?'

    The gradient of the river here is 9?. The velocity, width and depth are in the following table: Width (m) Depth (cm) Velocity (flow rate in seconds) 0 5 0.25 10 40 0.50 22 12 0.75 23 14 1.00 5 Average Velocity 22 Here is the channel profile for site 1: The wetted area for this site is 0.14m?.

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

    Radius; 15,750cm =20 792cm Arncliffe; The table below is taken from the graph, 'Distance between River Skirfare Surface to Riverbed at Arncliffe'. (Graph 1. b) Arncliffe Distance Surface to Riverbed 1250 59 200 30 1300 51 250 60 1350 42 300 57 1400 40 350 59 1450 41 400 69

  1. To what extent the flood alleviation scheme has had on the environment and people ...

    Human activity means that there is a lot more surface run off, due to the impermeable concrete and tarmac ground laid when urban areas are built up. This means that infiltration is reduced while surface run off is increased. Deforestation is also common in urban areas, so not only is

  2. The Causes Of Rainfall

    This process is demonstrated in the diagram below. The diagram shown above is the process of adiabatic cooling in the condensation process. For condensation to occur the air must be saturated (cooled to dew point). Dew point is the certain temperature to which air must be cooled in order to reach saturation.

  1. Investigation of the distribution and abundance off reshwater invertebrates in the Tillingbourne River at ...

    We may not have been able to catch all of them because they are extremely fast swimmers and there were 152 more shrimps found at the edge than at the middle.

  2. Do the Characteristics of a river change downstream?

    There should be more precipitation in general. The average annual rainfall in the Wharfe catchment area varies from 1835mm on Fountains Fell to 590mm at Cawood. There are no prominent instances of land use either side of the stream although most of the land is used for either sheep and goat grazing or simply footpaths used by walkers and hikers.

  1. Letter to the World Bank - What are the causes and effects of flooding ...

    River blocked means their channels are made shallower by the deposition of silt. The river has been damned in India. This has reduced flow in the dry season and increased deposition. The silt now blocks the river channels. High tides and storms this happened at the same time as the flood, which made it a lot worse.

  2. Should drainage basins be managed or natural? Discuss with use of examples from both ...

    There had to be some kind of management to keep order over who was using what water. In the 1920s an agreement between the 7 states was developed, it allowed any state to build a dam and use the water as long as it didn't take water away from a dam lower downstream.

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