Can 1,000 Boats Really Push the Chao Praya River Out to Sea Faster?

[HomeyG]

My understanding is that a bridge pier may slow down the water directly behind it, but doesn't slow down the whole river. After 30 meters or so, the effect is completely wiped out and the overall flow is not effected.

Why would a prop be any different? It's not. After a handful of meters the acceleration is completely absorbed as if it didn't happen. What possible good is it to increase the surface flow for such a small area?

Seems to me that they are lucky it doesn't work. If it did, if would be creating more surface waves and more water overflowing the banks. Remember this is not a uniform pipe, this is a meandering river with turns, changes in depth, width, and elevation.

Where are these bottlenecks? The whole area is in danger not just a few 30 meter spots along the river.

 

[DaveC426913]

Why do they need the whole boat? Why don't they just take the engine out? If you hold it down, it doesn't need to float.

Because the boats are already there. The reason this is being experimented with is because it's quite easy to do with little additional cost.

 

[xts]

My understanding is that a bridge pier may slow down the water directly behind it, but doesn't slow down the whole river. After 30 meters or so, the effect is completely wiped out and the overall flow is not effected.

That's not true. Bridge pier does not slow flow - just contrary, water flows faster under the bridge than on open wider part. But it introduces significant resistance to the flow, effecting with damming of the water. You may better see it on smaller rivers flowing more quickly than Chao Phraya: the water levels before and after the bridge often differ by 20cm or more - which is equivalent to average level difference on over hundred meters along the river.

Boats (or other high flow pumps) installed in such bottleneck places may help to reduce (unload) this damming, thus making the slope higher on open area, which speed the whole river.

Such effect is even more important on very flat (low slope) rivers like Chao Phraya - here every 1cm saved on damming under a bridge increases then the natural gravity push for the river by 10% on next 2km.

Where are these bottlenecks? The whole area is in danger not just a few 30 meter spots along the river.

Bottlenecks are points where the flow encounters in a short area strong resistance, stronger, than average on hundreds meters, causing damming of water - even very small, like few mm, may be worth to reduce on such flat river.

 

[HomeyG]

Thanks for the explanation XTS.

I still have a hard time believing boats are making any difference, but I appreciate you trying to explain it to me.

 

[xts]

Well - I am not sure how effective it may be on so large river like Chao Praya.
But it was used successfully on 100 times smaller (and much faster) rivers using just single pumping boats.
So I can't say if they may improve the flow by 1% or by 10% using that 1000 boats. But for some people even 1% improvement may mean that their houses stay dry - I saw TV this morning showing the water flooding streets of Bangkok already.