Hard vs Soft engineering

 Hard and Soft Engineering: which is the better option?

Hard engineering: strategies involve the use of technology in order to control rivers. 

Soft engineering: adopts a less intrusive form of management, seeking to work alongside natural processes.

Hard engineering:

Dams/reservoirs

How does it work?

Water can be held up behind the dam following heavy rainfall and then released slowly to prevent flooding and for other purposes. 

Benefits

• Highly effective and very successful way of controlling flooding but also normally part of a multipurpose project which can include hydroelectricity generation and the storing of water to supply for domestic, industrial, and agricultural consumption. 
• By producing electricity, Dams also generate a long term income.
• It is environmentally much cleaner energy than electricity produced by coal and gas fired power stations and much more sustainable
• They provide recreation facilities for water sports, picnic facilities and other social activities. The bigger dams such as the Hoover Dam are tourist attractions. 
• Reservoirs store water during periods of heavy rain, reducing the risk of flooding. 

Costs/Disadvantages

• A flowing river will carry silt which backs up and is deposited behind the dam, which reduces the storage capacity and is expensive and time consuming to remove. It can lead to erosion further downstream and can change the chemical composition.
• Where water is diverted into the dam from other sources, it can affected the eco system of those rivers and those rivers and the wildlife and land around them. 
• The water held back and unable to flow like a river is more prone to become polluted if surrounded by heavy industry, such as the Three Gorges Dam project in China 
• People and habitats are removed and displaced (often forcefully) and communities are lost forever to make way for the space needed for the dam, reservoir and power stations
• They are very time consuming to construct and require access to huge amounts of raw materials such as concrete and steeL. In many poor countries prone to flooding, dam construction uses up a large amount of that countries financial resources. The Three gorges dam in China cost $25.5 billion and the Dam building projects in Pakistan are estimated to cost up to $35 million. Even the much smaller Hoover Dam project cost nearly a billion dollars in today's money. 
• The cost of some dam projects has been calculated to be higher than the long term cost of any flooding that may have occurred. 
• They are very costly to maintain
• They can pose a risk if they fail and huge amounts of water are released at a time. 

Examples: Hoover Dam, Three Gorges Dam, China

Straightening

How does it work?

By artificially straightening out where a river meanders, the river is made to follow a new much more direct and shorter route and the water clears away from the area much quicker and is prevented from pooling. 

Benefits

• This avoids building on areas (often of natural beauty) and therefore has less impact on the environment and avoids the need to resettle communities.
• The channel is easier and faster to navigate.
• Reduces the risk of flooding as water moves out of the area quickly because it doesn't travel as far

Costs/disadvantages

• Changing the course of a river is fairly expensive and time consuming to implement and maintain.
• As there is a greater volume of water being carried faster and with more energy this can lead to a greater risk of flooding or erosion downstream. 
• Removing the pooling effect of the river can have a detrimental impact on wildlife habitats by removing wetlands and marshes. Can also have a negative effect on the bio diversity and water quality. 
• Often in urban areas needing the most protection the land is not available to straighten the course of the river. 

Examples: Between 1934 and 1945 the Mississippi river was straightened reducing the length of the river by nearly 150 miles. 

Soft engineering:

Flood warnings:

How does it work?

This involves having systems in place to monitor the weather forecasts and river levels in particular areas, and warn people when floods are likely to occur. Action can then be taken by those likely to be effected, for example by sandbagging doorways, raising vulnerable items or in most severe instances removing possessions or evacuating the area. 

Benefits

• Can be implemented very quickly 
• This obviously has minimal impact on the environment and is socially sustainable. 
• The costs are significantly less than hard engineering alternatives and also cost very little to maintain. 
• They have lower education and technology requirements so they can be implemented by local people and in remote parts of poor countries. 

Costs/Disadvantages

• It does not stop the flood from happening or the damage the floodwaters cause. 
• Flood warnings are usually communicated through the internet, television and radio and some people, including the most vulnerable, may not have access or simply may not be using it at the relevant time. 
• People do not always react how they should do to warnings

Example: Tewkesbury 2007 gave people valuable time to move possessions, turn off services and take precautions. 

Flood preparation

How does it work? 

The environmental agency monitors weather forecasts and river levels, and provides information on how to prepare for a flood and what to do during, and afterwards. 

Benefits 

• Having systems in place to provide sandbags, storm gates, door guards in areas prone to flooding reduces damage.
• Relatively quick and cheap to implement, as in particular it empowers individuals to take steps rather than to rely on the authorities. Enabling people to minimise the damage caused by the floods is financially advantageous and reduces the impact of the floods on peoples lives. It also reassures people living in flood risk areas and can reduce insurance premiums and improve insurance availability. 

Costs/Disadvantages 

• It does not stop the flood from happening in the first place. 
• It could give people a false sense of security 
• It is expensive to modify homes and businesses 

Example: The environment agency and all local authorities in the UK have flood risk assessments and preparation schemes in place. 

Flood plain zoning

How does it work?

The flood risk is assessed across different parts of the floodplain and the use of the land takes this into account. Deliberate flooding is encouraged on low value land such as marshes or grassland to prevent flooding of more valuable land downstream. 

Benefits

• If nothing is built on the areas prone to flooding there is nothing to be damaged and the area will soon return to its normal state. 
• If the floodplain is not urbanised infiltration can occur more successfully, and there is less surface run off to overwhelm the rivers. 

Costs/Disadvantages 

• This can have an adverse effect on planning, preventing development where it is needed and in particular houses being built in areas where there a huge shortages. 
• It does not help areas that are already built on. 

Example: following the flooding in Lynmouth in Devon in 1952, zoning was used to identify areas around the river most at risk from flooding. 

Do Nothing

How does it work?

This involves leaving the river to do just as it wishes, which includes flooding at times and to adjust or adapt to what happens. No money is spent on new engineering methods or maintaining current ones. 

Benefits

• Financially it costs nothing directly and humans, wildlife and plants are able to adapt to the changing environment. 
• It is environmentally friendly. As long as the flooding is not a direct consequence of human activity it can be seen as the environment changing and evolving. Many of the fantastic geographical features we enjoy such as marshlands, wetlands, valleys and deltas can be as a result of flooding. 
• Material is deposited from the flood onto the floodplain making the land more fertile.

Costs/Disadvantages

• The indirect costs of the damage to property and the environment and the social effects of flooding are high. The flood will cause a lot of damage. 
• Insurance costs for those living in the area are very high or unavailable. 

Example: Parts of Africa do not have the resources to implement schemes and often are forced to do nothing or very little.