The solution currently proposed is to build seawalls on the seaside.
But this solution has many disadvantages :
- These works are gigantic, and their cost is also huge.
- Populations would live in lands below sea level.
With risks in case of storm (for example Storm Xynthia, or Hurricane Katrina in New Orleans), or in case of seawall breaking.
- The drainage of the rivers flowing into the seas will become also problematic,
and it should be necessary also to dam these rivers.
In the long term, elevations of 6 to 8 meters for sea level are envisaged by some scientists.
So for such heights, seawalls will be exceeded.
The project cost "Polar solution" is very low compared to the construction of seawalls, or loss of towns, of ports, of cultivatable soil, etc.
In many cases, seawalls to build cost more than the value of the protected area.
New Orleans is a good example of what will happen in many places. The cost of seawalls built after Hurricane Katrina is a good example.
Some examples of dams :
- New Orleans after Hurricane Katrina,
- the Moses project in Venice,
- the dam on the River Thames in London,
- seawalls in the Netherlands,
- mobile seawalls in St Petersburg.
If the solution used is the construction of seawalls, the cost will be pharaonic, the term "pharaonic" is even inadequate, because construction of pyramids will seem to be a joke face to the length, and the height of the seawalls to build.
For example often seawalls are made with large blocks of rock.
Make seawalls on sandy subsoil is useless, waves erode the base and undermine seawalls. The subsoil gives way under the seawall.
An example : bunkers built during World War II.
When the sand at the base is removed by sea, bunker sinks or toggles.
So seawalls will have problems of this type.
Furthermore in some cases, water can infiltrate under seawall and ascend by capillary action, so seawalls would be ineffective.
Moreover, containment of rivers that flow into oceans and seas must be made (Rhine, Rhone, etc) because of sea level rise, they will flow less near the sea.
A concrete example : Camargue.
Beaches would be lost, so this area that lives from tourism would lose its revenues.
Seawalls comport risks. A seawall rupture would have an effect equivalent to a tsunami.
We have seen consequences of the New-Orleans's flooding.
In the Nederlands, January 31, 1953, the sea has passed over seawalls, there were over 1800 deaths.
All along the history of the Netherlands, there were seawalls breaks.
For example, during World War II, after bombings.
In the long term, sea level rise is unmanageable with seawalls.