"I think this is the same USACE that is managing to keep the flow of the Mississippi River in its channel flowing down through Baton Rouge and New Orleans, instead of shortcutting and taking over the Atchafalaya River channel and drying up NO as a port."
Exactly. They are the ones trying to nail down a river. Preserve the status quo. And spending a lot of money doing the same ole same ole. Instead of trying to restore wetlands by allowing some drainage through the Achafalaya, they have insisted, until now, on preventing even a single drop to go through the slough. There has been, in the last few years, controlled experiments allowing some flow through at peak times, and the results were positive beyond their belief. No on-going program that I know of will have any chance of sucess as long as the mentality if to maintain the river the river only in the bed it now occupies. Granted, development and economic interests won't allow a fre-flowing river. But using the river as a cheap dredge has it's cost too.
The link you provided does mention piping, exactly one time. The dikes along our rivers are small compared to what I saw in LA. Many of them consist of a low earthen berm in the downtown areas of some of these PA towns. Far far from the massive earthworks along the Mississippi. The main thrust of that link was to point out that if you allow vegetation to grow, you will not be able to inspect the face of your levee. Again, if trees are grown at the foot of a well built levee, the roots will penetrate how deep? If the original soil line is dug out, and the right kind of fill used, roots will barely scratch the surface of the soil. Trees grown at the bottom of a 35ft levee go how deep? Piping will occur on small dams, of course, but one can hardly imagine a situation where a wall of dirt (from the underground base) 40ft/12m tall and how wide? is penetrated by tree roots. Groundhogs have lived for decades in pond dams around here, and although some do fail, most dams remain.
How has it been established that the levees were mowed? Mechanical means were only invented in the very late 1800's, before that, hand scything was used. Any records of payments to scythers? Animals would have left the woody plants. Gangs of prisoners maybe?
I am very skeptical of the Corps because they have been shown to be a politically molded governmental agency with an agenda. Time after time they have been scolded by Congress in public hearings, and some of their top brass was removed for lying. Many projects that they fight for are of dubious benefit, politically connected, redundant and the result of turf battles.
It could very well be that piping is a worry in these particular cases. But I would not rely on the USACE to tell me without some other source of info. They have lied too many times. They have a vested interest in maintaining ever higher, wider and longer levees. Experience has not taught them that sometimes they can work with nature instead of always trying to muscle it into doing what they want.
In this case, they have not proven a single instance of piping, but want to cut down all the trees? Where are the instances of levee failure because of trees. If maybe, mights and could be are used to define a problem, then they should just abandon the whole thing because what if the city floods in spite of their work? What if ship wakes are shown to be crumbling some levees? Should the ships be banned? The cause as much damage as trees.
