Author Topic: Is the STCC hiding CRITICAL project information from it's Members?  (Read 210 times)

Michael Caswell

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Another expert is misquoted - again.
« on: November 28, 2018, 02:49:54 pm »
I wrote to Dr David Rosgen and he replied.

Here is the correspondence.

From: Michael Caswell []
Sent: Wednesday, November 28, 2018 8:29 AM
Subject: For the attention of Dr David Rosgen

Dr Rosgen
I note Harvey and Elizabeth Agte's group (Stop The Clear Cut) have contacted you as a possible advocate for their mission.
This group of people have blocked the NYPA (New York Power Authority) NYCC (new York Canal Corp) with a court injunction to stop the vegetation removal project in the three towns of Brighton, Pittsford and Perinton NY.
They persuaded  Professor Donald H Gray to sign a testimony stating trees were good for the embankments of the canal, offering stability etc. etc.
When I read his testimony, I felt there was something basically wrong because it flew in the face of the ASDSO, USACE, FEMA and NYDEC guidelines for embankment dams.  So I wrote to Dr Gray and asked him if he could show me any of his papers where it stated trees helps prevent erosion, and he sent me back his article on trees and levees.
So, I then asked him to explain to me the difference between an earthen embankment dam and a levee, and here is his reply.
Note in particular his statement ----
I dont know of any earth dams where woody vegetation was purposely planted or allowed to grow on a face of the dam.

When I pointed out. to Dr Gray that his affidavit was referring to levees and he had not been told this was an earthen embankment dam with a serious vegetation problem and had not been inspected for over 20 years, he rushed to seek legal advice.  The STCC had conveniently omitted to tell him that this was a dam holding up millions of gallons of water, directly over a built up residential area with hundreds of properties and a school in harm's way.
The NYPA's recent inspection by a dam engineer which rated it as a class 3 Hazard dam, and noted that further inspection was impossible because of the dense vegetation which they recommended should be removed.
You can see the state of this embankment here
It is also worth mentioning that the great majority of the vegetation here is junk Cottonwood, Amur Honey suckle, bittersweet vines, swallow-wort, and black locust, all invasive, or regulated by NYDEC.  The Cottonwoods are particularly dangerous because they are weak limbed, prone to toppling and compromising the embankment, a very dangerous situation on a 100 year old structure that has seen NO maintenance in seventy years.  The slopes are very steep, badly designed, there are no toe drains and leak abound everywhere.
One leak was so bad, a huge swamp was at the base of the embankment, right behind an apartment complex. It had a forest of cat tails growing there that was over 50 feet across. Back in the spring of this year the NYPA pounded 45' long sheets of steel into the crest of the embankment for a 200 foot length to stop the flow of water and shore up this mess.   I reckon it must have cost at least half a million dollars.
I hope I can persuade you not to support this group. They have cost the taxpayers a great deal of money, and put thousands of people's lives at risk.  The removal of vegetation on the canal is vital to the safety of the folks living below this nightmare. Much work is scheduled, like new toe drains, root removal, regrading steep slopes, filling in gouges and restoring spillways and culvert etc. etc. The work is ongoing in all other areas except where the STCC has persuaded town supervisors to mount this injunction. 
If you'd like to see this for yourself, I'd be glad to show you around in person or on Facetime.
Thank you.

Michael Caswell
Erie Canal Neighbors Association

Here is his reply
On Nov 28, 2018, at 11:45 AM, Dave Rosgen <> wrote:

Michael,  My research data and model represents lateral streambank erosion rates observed along stream systems and canals associated with (or without) riparian vegetation.   My data, however, does not reflect on a Dam embankment with a differential head influencing pore water pressure processes. 
Where cottonwood trees have been removed along embankments of irrigation canals, the results of such have increased bank erosion rates and required rock rip rap to offset the accelerated erosion of the embankment material.  It sounds like there are two different issues here related to vegetation influence.  If you have invasive vegetation along diversion canals or streambanks, spot spraying and planting of willows or other native woody vegetation to replace the invasive species is often recommended.  Willows also can out-compete many invasive plants without losing the bank stability associated with the effective rooting character of woody vegetation. 

Your dam face, however, is a different problem where head pressure can cause native material fill breach.  My previous recommendations were based on canal and stream channel processes only.  If wind-related wave action causes embankment erosion of the dam, surface protection of the dam face (including the toe) is normally required involving rock or material to dissipate flow energy.  It is important to identify erosional processes related to embankment failures, then design solutions that offset the risk of failure mechanics that address the cause of potential failure.  Soil mechanics must be investigated on earthen dams to help identify such failure mechanics and erosional processes and associated risks. 

My discussion was meant not to defend or support extreme views (or take sides), but to extend facts and research results on the role of vegetation related to streambank erosion related to streams and canal embankments.  I would not support the removal of  woody vegetation along stream channels and/or canals based on my research data of such. 

Dam embankments of native fill represent different processes and as such, vegetation can represent  a risk to stability due to water piping and positive pore water pressure failures. 

I hope this clarification will help in the proposed decisions to be made. 

And finally-

From: Michael Caswell []   12.52 pm nov 28 2018


Your findings explain everything perfectly, and are in total agreement with Prof Gray's stand.  He describes the effect of lateral erosion of canal embankments (not embankment dams) and streams as 'scour'. Of course it makes sense that the tree roots would assist in preventing erosion in this situation.

However, a earthen embankment dam suffers from 'head pressure' and is a completely different scenario than a canal embankment channel. Unfortunately the STCC group fails to understand the difference, so I'm glad you pointed it out to them.

This confirms the stand of the NYPA, FEMA, ASDSO etc. who all state ' No trees on an embankment dam - only grass'.

Many thanks

Mike Caswell
« Last Edit: January 10, 2020, 09:18:02 am by Michael Caswell »