3. How do we control flooding? Hard engineering projects are ones that involve the construction of artificial structures that, through a combination of science, technology and a bit of brute force, prevent a river from flooding. Soft engineering projects are the opposite. These projects use natural resources and local people’s knowledge of the river to reduce the risk posed by a flood. Often they are more sustainable

4. Hard Engineering Floods can be controlled in many ways: 1.Dams – control, store + release water 2.Straighten river – allows speed of river to increase 3.Build barriers – such as concrete embankments or Levees 4.Divert the river– pump water into stores or diversion channels/spillways 5.Widen + deepen river – so the channel can carry more water

10. What do you have to consider before building river defences? How often the river floods How much each method would cost Who would benefit from building defences? How bad is the flooding Who would lose out from defences? Are they good for the environment?

11. Cost Benefit Analysis What is the magnitude/frequency of the flood? Population in danger? Major communications (roads) in danger? Cost of damage (predicted) Cost to defend (multiple options considered)

12. Type of defenceCost 1=low 10=high Appearance 1=natural 10=ugly Environment friendliness 1=good for env 10 = bad for env Effectiveness 1 = very effect 10 = not effect Total score Higher the score worse the defence type Build concrete flood walls to hold rising waters Build a dam tohold flood waters back Straighten river so water moves along it quicker Buildearth embankments to stop river flooding Widen and Deepen river so that it can carry more water Plant more trees that slow down water reaching the river Stop people building on floodplains where flooding is worst

13. Aswan High Dam Was it worth it? A case study of water storage and transfer in Egypt (an L.D.C.) Acknowledgement to : The Geography Portal site

14. Location Aswan is about 600 kms south of Cairo the capital of Egypt. Where is… The delta The flood plain The desert areas Libya Sudan?

15. Facts The Aswan High Dam is 3600 metres long and 111 metres high. The Soviet Union helped the Egyptian government to build the dam. The Aswan High Dam has 12 turbines which generate over 10 billion kilowatts of electricity every year. Construction started on the dam in 1960 and it was completed in 1971. 30 000 Egyptian people worked day and night to build the Aswan High Dam. Lake Nasser was created behind the Aswan High Dam. It is the largest artificial lake in the World (560 kms in length). It is named after Gamal Abdul Nasser, the former President of Egypt.

16. The Aswan High Dam Project in Egypt, which was completed in 1970. The dam is built on the River Nile and provides: Hydro-Electric Power (HEP) Irrigation water for surrounding farmland Water supply to the population Flood control. i.e. A MULTIPURPOSE SCHEME

17. The Advantages of the Aswan Dam There are many advantages of the Aswan Dam. These are shown on the spider diagram below :

18. Helping Egypt to develop: The formation of the Lake Nasser reservoir creates HEP opportunities and controls flooding. This helps Egypt to develop in two ways. Firstly it provides the electricity needed for people and industry to increase their quality of life and to stop the flooding which ruins so many livelihoods and claims lives.quality of life

19. Electricity for homes and industry: HEP is used to generate electricity that is taken to homes and industries by pylons. Aluminium and copper smelting industry

20. Flood control: Control of flooding is carried out by the dam. By keeping so much water back in Lake Nasser, the River Nile rarely floods the surrounding farmland any more.

21. New farmland created: The act of keeping back the water from the River Nile has lowered its level, effectively creating new farmland by the river sides. This is also less prone to flooding.

22. Irrigation water for nearby farmland: Development of irrigation channels from Lake Nasser, takes water from the reservoir to the nearby desert to make farmland for watering crops. The electricity pumps the water there.

23. Fish stocks in Lake Nasser: Fish live in the lake and can be fished more easily by those fishermen who used to fish in the River Nile. This should improve their livelihoods and fish stocks can be replaced more easily. Also creates tourism via ‘game fishing’.

24. The Disadvantages of the Aswan Dam There are many disadvantages caused by the Aswan Dam. These are shown on the spider diagram below:

25. High set-up costs of building the dam: Egypt had to borrow a great deal of money to set this dam up from the Russians. Egypt will be repaying the loans back for a very long time and so it is doubtful whether this will help Egypt to develop at all

26. Irrigated farmland suffers from salination: When water evaporates in these hot areas, it brings salts to the soil surface. This is called salinisation and it is not good for the soils or the crops. If too much salt rises to the surface, it can kill the plants and reduce yields.

27. Water-borne diseases increase: As the water in both the reservoir and irrigation channels is contained and in a lot of places static, this promotes the build up of water snails which carry the disease bilharzia. Many other diseases also increase as they are not 'flushed away' by the flow of the River Nile.

28. Land lost from flooding of Lake Nasser: Although there were some land gains from the building of the dam, there were much more losses behind the dam where the land was flooded to make the reservoir of Lake Nasser. Many people were moved and made homeless as well as losing their farmland. The temples of Abu Simnel had to be moved.

29. Evaporation from Lake Nasser is very high: This is an extremely hot area of the world. Evaporation from Lake Nasser is very high as a consequence and this means a lot of water is lost.

30. Silt builds up in Lake Nasser: Silt, that would normally make its way down river gets trapped behind the dam, lowering the level of the reservoir. In addition, this silt would have made its way onto farmland and onto the Nile Delta and this is now causing farmland to become less fertile and the Nile Delta to stop growing. Also, Cairo brick makers are suffering as they no longer have enough silt deposits to make their bricks from. Mud brick village

31. Natural flooding / silt is lost: Flooding is an important natural event which enables silt to be placed on farmland, making it more fertile. Without this flooding, the farmland in front of the dam is becoming less fertile. Yields of crops will drop and eventually people may lose money or starve. In addition, those who do not have the luxury of an irrigation channel, will suffer from a lack of water entirely.

32. Channel Straightening In a simple form, the river has its meanders removed to give a straighter course. In most cases, this process will be done at the same time as channelisation where the new course is lined with concrete

33. This increases its hydraulic efficiency and allows a larger discharge to be contained within the channel. This wil hlep prevent flooding. The channel can be made straighter, through the use of artificial cut-offs. The channel can be realligned to artificially increase the long profile gradient so that there is an increase in velocity and flood waters can be removed more quickly, which speeds up the flow and also aid navigation.

34. This process not only speeds up the flow of water away from the area, but reduced erosion so ensures more of the capacity of for water instead of sediment. The downside to this is the loss of the natural looking river. It also causes water to arrive more quickly further downstream which increases flood risk and erosion in this location.

35. Kissimmee River - Florida 1960’s Result was devastation to wildlife 2014 – Destroying the straight route

36. Mississippi Late 1800’s Several floods since then proved that this method alone was not always effective

37. Levees Artificial levées are, well, artificial versions of their natural counterparts. They act as embankments, essentially extending the channel’s height and increasing its bankfull discharge. Unlike natural levées, artificial levées are significantly larger and are generally constructed out of a material like concrete or compacted earth that is resistant to erosion. The main advantage of an artificial levée is that it allows the floodplain to be built on. This is their downfall though as they encourage the development of the floodplain which can increase the risk of flooding. Furthermore, if they did fail, like the embankments along the Mississippi did in 1927, the damage from the flood would be far worse than if the embankments didn’t exist.

38. What are the purposes of artificial levees? The main purpose is to prevent flooding of the river into the adjoining land. What are the characteristics of artificial levees? They are built on a cleared, level surface using piled earth. They are broad at the base, triangular shaped with a level top on which sandbags are placed. Their surface must be protected from erosion to ensure the levees are maintained, thus vegetation such as ‘Bermuda grass’ is planted in order to bind the piled earth together. Artificial levees

39. Existing artificial levees Examples of existing artificial levees include along the Mississippi river and Sacramento rivers in the USA, as well as the Danube and Loire in Europe. The artificial levee along the banks of the Danube, Germany.

40. Mississippi, USA It is the one of the largest levee systems in the world. The levees are 3,500 miles long, extending 1,000 miles along the Mississippi river. They measure 24 feet in height with some as much as 50 feet.

41. What are the causes? The breaking of levees High rainfall causing higher peak flows. High winds which cause the ocean or river to swell, causing it to crash over the levee. What are the characteristics of a broken levee? When the water has ‘overtopped’, or risen above the crest of the levee. Levees may also suffer a fracture A broken levee in New Orleans, USA

42. A broken artificial levee on the Mississippi river, USA A broken natural levee in New Orleans, USA Both natural and artificial levees can be broken by natural force.

43. 1993 Mississippi The flood of 1993 saw a huge debate about whether the levees had been a waste of money. Huge flooding occurred and the levees had been the main flood prevention method of investment

44. The engineering corps felt that the levees had done the job they were designed for in that they were built to a budget based on risk analysis. The 1993 flood was seen as an exceptional event that the levees had not been designed to cope with. Had they been built higher (at far greater cost) they would have worked. Others argued that many levees broke before the water reached the top suggesting poor maintainance, design or construction

45. Discuss Should they have built the levees higher?

46. Diversion Channels (Spillway) http://www.youtube.co m/watch?v=4bzAE9O qvyMhttp://www.youtube.co m/watch?v=4bzAE9O qvyM Diversion channels involve digging out a channel to assist water away from flooding a settlement. They are often combined with pumps or retention areas that act like mini reservoirs to hold back some water

47. Big Sioux River – South Dakota 25km spillway to protect the city of Sioux Falls

48. Jubilee River (Diversion) 2002 £80m Developed new wetlands so improved the environment and has also improved recreation in the area. Where does the soil go?

49. Dredging, widening and deepening Boscastle Increases capacity Often needs to be done in tandem with future dredging due to deposition (although channelisation can assist)

50. Homework Read and notes on p53-56 (add to class notes where applicable) Do the research task on p56 to hand in

51. Look at the approaches to flood prevention and complete the sentences below I think the cheapest project is…..because… however, I think… is the most expensive project because….. The best project for wildlife is…… as/because… whereas the project which is best for the river’s appearance is…. because…

52. BANGLADESH MANAGING THE FLOOD SHORT TERM Bangladesh Government Distributed money and 400 tonnes of rice Relief supplies of fresh water, water purification tablets and sanitation services provided Aid Agencies Provided Boats to rescue people Supplied medicines Supplied clean drinking water Set up a medical treatment centre Distributed fodder for livestock Distributed food and plastic sheeting Planned a rehabilitation programme to repair and construct housing and provide sanitation Other Governments Gave aid including wheat, money, medicines, water tablets, house repair, sanitation and rehabilitation for farming and fishing

53. BANGLADESH MANAGING THE FLOOD LONG TERM In 1989 the Bangladesh government working with several international agencies and the world bank produced a FLOOD ACTION PLAN (FAP): SHELTERS AND WARNING SYSTEMS Built 5000 flood shelters in high risk areas Improve flood forecasting system using satellite and computer technology Prepare flood disaster management plans which provide early warning and clear, effective instructions as to what people should do before, during and after a flood DAMS Building 7 new dams to control river flow and to hold back the monsoon rainwater in reservoirs The water would be used for irrigation and generating electricity

54. BANGLADESH MANAGING THE FLOOD LONG TERM cont… Flood Control 12-15 floodwater storage basins to hold floodwater diverted from main rivers Divide the land into compartments and control water flow through a system of channels by sluice gates and water pumps In the dry season water can be moved to farming areas requiring irrigation Embankments Complete and strengthen the embankments along all the main river channels to a height of up to 7 metres More than 7500km of embankments are already in place but repairs, heightening and new building would cost over $6 billion Other controls Pumping water out of the ground in the Himalayas during the dry season to create underground storage for the monsoon rains Replanting of forest cover in Nepal and Tibet

55. BANGLADESH WHAT DOES THE FUTURE HOLD? Debate between ‘HARD’ and ‘SOFT’ engineering flood prevention schemes continues Many oppose the FAP both locally and internationally: Embankments will trap rainwater and make flooding worse! Dam construction could increase the build up of silt and make flooding worse How can we provide solutions if we don’t really know the causes? These plans are far to expensive! Embankments restrict river access for fishing people Flood control systems may damage the environment Half a million people will lose their land to reservoirs and embankments! Flood shelters save lives but don’t help protect our property and livelihood