http://en.wikipedia.org/wiki/Seawall
http://tinglefactor.typepad.com/.a/6a0120a4f9a8ff970b01348632fedd970c-pi
http://www.georesources.co.uk/seawall.gif
http://www.dnr.state.oh.us/Portals/7/pubs/fs_gifs/stfs16fig1.gif
2011-06-28
URL of used website
Conclusion
In conclusion,
we have learnt different kinds of seawalls and their different purposes. (E.g curved seawalls, vertical seawalls and mound type seawalls)
we have analyzed the effectiveness and the ineffectiveness of different kinds of seawalls. (E.g a strong defence/costly, can be used for sightseeing/eyesore)
we have thought up problems that seawalls face. (E.g extreme events like tsunami, storm and rise in sea level)
we have found some examples of seawalls. (E.g Vancouver Seawall,Canada & Seagrove Bay,UK)
Even though seawalls are useful for our daily lives as they provide denfence and safety, seawalls still have some insurmountable problems such like extreme events and rise in sea level. Thus, we should choose correct seawalls to be built in appropriate places to exert seawalls' optimum efficiency and to make the best result.
2011-06-27
Seawall in Qingdao,China
This picture of seawall was taken in Qingdao, China.
This seawall is a curved seawall. We can see that the seawall is curved built at the upper part. From my observation, it was built in concrete and steel.
This design of seawall enable waves to break to dissipate wave energy and to repel the waves back in to the sea. It can also prevent the wave over-topping the wall and provide additional protection for the toe of the wall.
2011-06-26
Problems that seawalls face - 3 -
Other Limitations
Some further limitations include:
*lack of long term trend data of seawall effects due to a relatively short duration of data records
*modelling limitations
*comparisons of different projects and their effects being invalid or unequal due to different beach types;materials; currents; and environments (Christchurch City Council, 2009).
Problems that seawalls face - 2 -
Extreme Events
Extreme events also pose a problem as it is not easy for people to predict or imagine the strength of hurricane or storm induced waves compared to normal, expected wave patterns.
An extreme event can dissipate hundreds of times more energy than everyday waves, and calculating structures which will stand the force of coastal storms is difficult and, often the outcome can become unaffordable.
For example, Omaha Beach seawall in New Zealand was designed to prevent erosion from everyday waves only, and when a storm in 1976 carved out 10m behind the existing seawall the whole structure was destroyed (GeoResources, 2001).
Problems that seawalls face - 1 -
Sea Level Rise
Sea level rise creates an issue for seawalls worldwide as it raises both the mean normal water level and the height of waves during extreme weather events, which the current seawall heights may be unable to cope with (Allan et al. 1999).
The International Panel on Climate Change (IPCC) (1997) suggested that sea level rise over the next 50 – 100 years will accelerate with a projected increase in global mean sea level of +18 cm by 2050 AD.
This data is reinforced by Hannah (1990) who calculated similar statistics including a rise of between +16-19.3 cm throughout 1900–1988.
This problem could be overcome by further modelling and determining the extension of height and reinforcement of current seawalls which needs to occur for safety to be ensured in both situations.
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