- High Tide
A daily tide which comes and in and out of the sea. This is a major threat to the people living around the area as it can be very high, which sometimes rises above all the barriers and walls which causes severe floods. This is because the river is tidal over its last 8.8km.
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London Clay
London is built upon an impermeable material, clay. Clay is impermeable because it does not let water pass through. This is a rising problem as the water is getting stored on the clay which helps contribute to the risk of flooding.
- Spring Tides
A different form of tides which occurs specially during the spring term. This occurs because the last 8.8km of the river is tidal (same reason for high tides)
Human factors which increase the risk of flooding
- Deforestation
In the past the land use in Lea Valley drainage basin was forest and farming. However over a period of time the land use has changed. Now it is more urbanized which has more local businesses and industries within the catchments area. People cut down the trees which reduced the risk of flooding because it slowed the process of the water reaching the river, this was due to the trees absorbed the water through the roots and also they barricaded the water which would slowly get through to the river in diminutive amounts.
- Urbanization
Urbanization was the reason for deforestation (shown above). This increases the risk of flooding because already there are 2million people living within the region which attracts businesses and industries to grow. Also because of urbanization, it has led to an increase of impermeable surfaces. Already London is built over clay (which is an impermeable material), however more impermeable surfaces are being built such as tarmac roads, which mostly help transport like cars but increases the risk of flooding.
- Drainage system
The drainage system is the route all our waste takes to the river. However it is also a shortcut for water to reach the river. When there is too much water above the London clay what tends to happen is the drainage basin deposits the water in the river leaving it to flood.
How can the flood risk be managed?
There are many ways in which you can manage the flood risk in the river Lea, ‘although you can never get rid of it’ (words from the environmental agency).
Below is ways which show how you can reduce the flood risk in the river Lea:
- Afforestation (vegetation)
Planting trees and vegetation such as reed beds and willows will help decrease the risk of floods. The reason for this is that by planting reed beds and willows on the river bank, they can absorb the water and also it can protect the river bank. This is a great advantage because it has a positive affect on the natural habitat, as they will increase. Furthermore it is an advantage because reed beds contribute towards filtering the water, making it cleaner for the fishes and other wildlife in the water. Moreover I think Afforestation would help because it will slow the process of the water reaching the river, which will further cause the reduction of the drainage system because it would not be used as a shortcut to the river.
- Raised banks (river walls)
Raising the river walls is an option, however to do that it would be very expensive which is a major disadvantage. Also by doing this you can control the floods but there is still a possibility of flooding which will then lead to raising the banks even further and further every year, which wont be an ideal and an effective idea.
- Water diversion scheme
This is when water from one place can be transferred to another place using a channel which joins both areas up. This is going to be a very expensive method because a new diversion channel has to be created for this. Also it wouldn’t be very effective as other methods such as Afforestation. The reason is that it’s taking the flood risk somewhere else.
- Straightening and shortening the river course
This method is and extremely expensive idea. It would take a long time to implement, by that time if there is a major flood it would destroy the work that’s in progress. Furthermore it would make the river faster, and shorter. This still allows the river a great possibility to flood.
- Other
There are other methods to help reduce the flood risk which is listed below:
Widening the river navigation Sluice gates Channel improvements
Constructing a new weir at Hertford basin Structures Thames Barrier
Flood lagoon area upstream of New Gauge Flood Channels Dredging
3 Mills and River Lea Flood Management Scheme
To reduce the risk of flooding in the river Lea, there have been four management schemes which have been implemented. We went there to visit the management schemes site. The management schemes were:
- 3 Mills river wall (site 1)
- Flood relief channel- Prescott channel (site 2)
- Plantation of reed beds (site 3)
- Raised banks.
(These sites have been marked on the map below):
3 Mills wall River
The advantages of the 3 Mills wall river is that it keeps the water overflowing, unfortunately the disadvantages is that it is not environmental friendly and also its not very nice to look at(unattractive).
This site is unnatural due to the wall, also it’s seems unnatural because it has unattractive warehouses at the back. However it does have a couple of trees in the background, which shows some of nature preserved in this site. Furthermore this site does not have any habitats as they will not be able to survive in a derelict site like this. On top of the silt are a few boats sitting. For safety the area has got a good reputation.
Below is the survey which I filled out when I visited the site, which shows my environmental interpretation of the site:
Below is an annotated image of 3 Mills river wall:
Flood relief Channel-Prescott Channel
the advantages of the Prescott flood relief channel is that it diverts the water through the channel, however the disadvantages is that it was very expensive to build, it was man made and it is not a very attractive sight.
The Prescott flood relief channel is a man made channel. The site is unnatural, as it consists of a lot of concrete (shown on the image below). Although he site does not look very nice is well designed structure which functions very well. The site is very dirty because it has dumped litter in the water, such as rubber tyres and Tesco trolleys. The site is maintained very well and is looked after.
Below is the survey which I filled out when I visited the site, which shows my environmental interpretation of the site:
Below is an annotated image of the Prescott flood relief channel:
Reed beds
A reed bed is an artificially created wetland planted with specially selected species of reed that have the ability to absorb oxygen from the air and release it through their roots. This creates ideal conditions for the development of huge numbers of micro-organisms which are able to break down any soluble material present.
Benefits Of A Reed Bed Sewage System
- A well designed, fully functioning reed bed system is a means of sewage treatment that:
- is efficient and cheap to run
- relies on biological processes
- returns solid matter to the soil
- recycles liquids in the form of purified water
- produces reeds which can be harvested for compost
- avoids the need for chemical treatment
- Encourages awareness of sewage disposal processes.
The advantages of planting reed beds are very great. The reasons for being are that it’s very efficient economically, they look beautiful and it’s all natural.
The reed beds are well designed as they did reduce the risk of flooding. They assimilate very well with the environment because they are natural. The reed beds are relatively clean compared to the other 2 sites. Although this site does have dilapidated buildings around it, it’s rather satisfying to look at.
Below is the survey which I filled out when I visited the site, which shows my environmental interpretation of the site:
Below is an annotated image of the reed beds which were planted:
For safety I would judge that the 3 mills wall river the best, unfortunately I don’t think it’s very attractive and clean. Out of all three sites this site has the most derelict land and also out of all three sites this site is the most badly designed and the most badly maintained site. In addition I would say that it is the most dirtiest and unattractive site.
The Prescott flood relief channel has some weaknesses and some strengths. The advantages are that it does not have much derelict land, it’s fairly safe, it’s well designed and well maintained. However it does have some disadvantages (weaknesses) just like every other site has, these are that the site is not as natural as it can be, it’s not very attractive and it’s rather dirty.
Using my analysis and the survey I filled out, I would judge that the reed beds was and is the best method to reduce the risk of flooding. The reason for this is that is natural, looks beautiful and is safe. Although it this site has not met my standards of being clean and also addition to that it does have derelict land around it. However it is the cleanest out of all the sites and the other sites do have the same problems just like the reed beds site.
Using the survey I have summed up a conclusion which shows the best site and the worst site. They are number below and go in order of best to worst:
- Reed beds
- Prescott flood relief channel
- 3 mills wall river
(Main) Natural Landforms
Mud flats-
Mud flats are very muddy areas beneath the tides (when they come in), when the tides go out the mud flats can be seen. Often in a mud flat you would see deposited materials such as stones and rocks, also in a mud flat you can sometimes see dead wildlife such as fishes.
Silt beds-
Often have a lot of algae growing on it. Silt beds are very fertile and have a lot of blood worms feeding off it (blood worms are red insect like creatures). The blood worms tell us the level of pollution in the area, for example when there is a lot of blood worms it indicates that there is a lot of pollution in the area. However when there is not much blood worms it tells us that there is not much pollution. The silt beds are vital in the environment, without it the blood worms would die. Also they are important in the environment because that is where Herons tend to sit and hunt for fish. Moreover they are important is because humans consign their boat there at times.
Island-
The Island is a natural landform because it is made from sand, stones, pebbles and other natural material which have been deposited by the river. The island is a rigid and a stable area because people built a chemistry lab on it once, which is now not in use and counted as derelict land. The island is important because it’s the habitat of a lot of animals, which include animals which fly and which don’t.
Reed beds-
Reed beds are plants which grow beside the river, along the river bank. The reed beds are used like a water filter since it cleans the water, decreasing the amount of pollution in the river. Also the reed beds contribute towards the flood management as it helps reduce the risk of floods. The reed bed is the natural habitat of many animals, one of which includes the kingfisher. The kingfisher is a bird which is very close to extinction in the area.
What is the impact of economic and urban development on the river?
In this stretch of the River Lea there are a lot of heavy, dirty, and unclean industries. They increase the level of pollution in the river. Also not far of the river is a scrap yard which deals with a lot of waste material, such as scrap metal. However this can help if it was used in an environmental friendly way and compromised. Due to there is so much scrap metal in the river such as Tesco’s shopping trolleys, the scrap yard people can come and collect the waste material which is left in the river which would decrease the pollution in the river, and would benefit the scrap yard.
Lately there have been an increase of housing estates in Lea Valley, this is trying to improve the look of the area, and unfortunately it attracts big businesses (Tescos) which does eventually lead to a steady increase in pollution.
Due to the increasing demands for sewers it has led to a major problem, when the sewers overflow (happens occasionally) you can spot raw waste in the river which contributes towards polluting the river. Also the smell of the manure is simply atrocious.
The 2012 Olympic proposal
The British Waterways (BW) head of boat navigation have put forward proposals to develop Lea Valley for commercial and domestic use. The proposals include raising the water levels for the Bow Back Rivers permanently and removing the tidal influence of the Thames, through the construction of a barrage. The construction of the barrage will also add to the level of flood control measures. The reason the BW want to increase the level of water is so that the area will look good and all the pollution will be hidden, such as the manure and the dead fish will be all underwater.
The proposal is linked to, though not dependant upon, London’s bid to host the 2012 Olympics. The outcome for this part of the waterway will be used mainly, for sporting, leisure and recreational purposes. For example they want an athletics village, media, ancillary parking facilities etc. They are aiming to build a major infrastructure (transportation network) and other services on of which is a cooling and heating centre controlling the climate for the whole area. Furthermore they want to build bridges and land bridges, to do this they will have to carry out major engineering works on the river and canals.
Arguments for and against the 2012 Olympics proposal
There are many advantages and many disadvantages of the Olympic proposal, which causes a lot of disputes. Some people argue for the proposal that it will make London a richer and wealthier place. Some people also say that the area would attractive if the works are implemented. Moreover people say that it’s a good idea because it will attract more big businesses to come and settle in London as their home, which lead to an increase of tourists which will flourish the tourist industries etc.
Another argument is that if the proposal goes through there will be much more people on the streets which will decrease anti-social behaviors and the need for police in that certain area. Additionally another argument is that it would have deep waters so people can go cruising in ferries and boats as a leisure activity.
Unfortunately there are major disadvantages for the Olympic proposal. On argument is that if the Bow Back Rivers are flooded there will be a major loss of natural resources and habitats for the wild, for example the reed beds would sink which will increase the risk of flooding. Furthermore if the Olympic proposal does go through then animals like their Kingfisher would loose their natural habitat this is a further disadvantage because Kingfishers are almost extinct. There will be many other arguments against the proposal which are increase in pollution due to the increases of businesses. Also without the wildlife the area would look monotonous. There will be more noise and conflicts with the users. The value for property within that region would increase rapidly. Furthermore the risk of flooding will be greater than it already is.
Can the needs for economic regeneration and habitat protection be balanced?
I think that economic development and habitat protection be managed, although only to a certain extent. The reason for this is that if big businesses want to move in then they should pay to help protect the natural habitat, and they should not exceed the limit of getting their business involved with nature. However I think this will not work because the businesses don’t care about the environment; all they care about is increasing their sales.
Will the proposal increase or decrease the risk of flooding?
I think the proposal will increase the risk of flooding greatly. The reason for this is that the Bow Back Rivers and the River Lea will have an increased level of water, to add to this one of their flood risk management has failed which was to plant reed beds, and the reason for its failure is because of the increased water level. Furthermore I think that the proposal will increase risk of floods. This is because more people are going to be attracted to the area, who will have certain domestic needs, which will contribute towards the flooding. Moreover I think that the proposal will increase the risk of floods is because of the London Clay. If there is a flash flood or snow the water will have to go somewhere, this water will go to the London Clay (beneath London) and will be deposited to the sea, causing floods in the area.
Conclusion
I think the 2012 Olympics proposal would do a great deal for the lower Lea Valley; the reason for this is that it will have more money incoming in the country and it will make the area much more beautiful and much safer than it is now. Another reason why I think it should go through is because that it will bring a people of variety of countries together to compete in one sporting event.
Although there are many nice things to say about the proposal I think that the area would be damaged very badly. The reason for this is that the river water levels would be very high which would cause constant flooding. Also I think that it would destroy the habitats such as removing the reed beds which will lead to the loss of the Kingfishers habitat.
Overall I think the proposal should not go through, because it would cause more damage than good. The troubles would not be worth it, and the losses are great in every manner. For example flooding will increase if it does go through. Furthermore I think the proposal should not go through because it will cause a lot of unchangeable damage which would be very hard to carry out. Such as increasing the sea levels to make it look good. Additionally I think that Lea Valley is a beautiful area and nothing has more than natural beauty. At the moment it has trees, water wildlife etc. However if the proposal goes through the businesses would expand so much that the whole area would be big grey buildings and cause Lea Valley to loose mother natures touch.