When the levee breaks .....

just seen the footage of the water lapping over the tops of the levee in New Orleans ...wow,

anorak donned - "how much does 10cm of the sea weigh on that wall ????"

do you mean ten metres ?


if so then its a simple calculation of a hydraulic load on the back of the wall which is shaped like a triangle (thick bit at the bottom) which is why dams are thicker the bottom than they are at the top. Added to this on the levee walls in New Orleans will be the kentic energy of the waves hitting the wall which will exert a different type of force on the wall and far higher than static water pressure.

I havent done this for a while so may be wildy out but I think its about 500KN per metre run of the wall (51 tonnes) acting about the walls centre of gravity, or centroid.

The maths for wave bit are quite complicated really. Lets just say its one strong ass wall

but how on earth do you work out the weight of the sea ?
any sea, be it black, red , pacific or South China ?

its all to do with angles of force. you dont need to know the whole weight of the water behind the wall only that water that will act upon structure or object you are analysing. So only so much water will influence the pressure exerted on the object be it the back of the wall or you in a swimming pool. The pressure in a swimming at ten metres is the same a the pressure in the in the sea at ten metres. In fact it would probably be less in the sea as if water is flowing then the pressure is reduced. (the higher the velocity in a fluid the less pressure is exerted) check out the bernoulli equation. the same effect is high an aeroplane wing works. are takes longer path over the top of the wing than on the bottom therefore as the wing speed in teh air is constant then the aire at the top of the wing must have a higher velociity than that at the bottom. Higher velocity above the wing reduces pressure and therefore the higher pressure beneath the wing lifts the plane.

I may of course be wrong in this I am sure learned members of the org will correct me if needed. (please do as I dont want to talk a load of b(ll*(ks)

[yorkie_chris]

Doesn't matter how big it is, pressure is function of depth so however large the sea you still have same pressure acting.

boy theres some brainy people on ere

They also don't think the levee's that have been installed after Katrina are up to the job.

Luckily when the current storm hit, it had gone down to a L2 storm. If it had been L3.....

But I also watched a program a few weeksback how they have been repairing the whole system, 24 hours a day, since Katrina.... People have been working for 6-7-8+ months without a single day off as they know if they don't repair it, the same thing will happen.