Posts Tagged ‘Levee Vegetation’

Levee Vegetation and Public Safety

June 11th, 2009

There is an Associated Press article out today that requires a direct response, because it is inaccurate in many ways. The article is about the Corps’ Levee Vegetation Policy, which has been in existence for decades.

First, let me just correct the record.

Error: The Corps ordered thousands of trees chopped down.

Fact: The Corps notifies levee project sponsors of operation and maintenance deficiencies, which may include vegetation, animal burrows, encroachments, and closure structures.  These deficiencies must be corrected to remain eligible in this voluntary program for federal rehabilitation and repair assistance following a flood. 

Error: The Corps “is on a mission to chop down every tree in the country that grows within 15 feet of a levee…..”

Fact: The mission of the Corps’ levee safety program is to make sure levee systems are reliable and do not present unacceptable risks to the public, property or the environment, with the emphasis on public safety.  The Corps has specific authorities for approximately 2,000 levees, or 14,000 miles across the country; not the 100,000 miles stated by the AP. 

Error: The anti-tree policy arose from criticism directed at the Corps after Katrina.

Fact: The Corps’ vegetation management standards are not new, and the Corps has considered them critical to flood damage reduction project reliability for decades. 

The bottom line is – Public safety is the number one priority of the Corps Levee Safety Program and the consequences of Operation and Maintenance issues, like having vegetation on levees, floodwalls or dams, go beyond the possibility of a breach or failure.  While vegetation and other encroachments can harm the structural integrity of the infrastructure, it can also obscure visibility for visual inspections, impede access for maintenance and inspection, and/or hinder emergency flood fighting operations. Operation and maintenance is a critical component to overall public safety.

I’ve seen levees with garages, storage sheds and pools built into them, and I’ve seen trees ripped out of a levee by flood waters.          

We’ve flood-fought levees where tree roots cause seepage through and under levees and where tree roots clogged critical drainage structures such as relief wells. We’ve even seen tree roots damage flood walls and steel sheet piling. Fortunately, we’ve been able to find these problems and intervene just in time with safety measures before the levee breaches but we must not rely on intervention, but provide greater reliability through well maintained infrastructure.

The bottom line with any levee system is that you are only as strong as your weakest link – so we must have clear policies and standards, which include vegetation management, consistently applied and enforced through continuous and periodic inspections and assessments.

The Corps’ policies on vegetation are based on available engineering and scientific data – and they have been validated with an Independent External Peer Review and Independent Technical Review.

Existing scientific literature doesn’t conclusively validate or invalidate our vegetation standards.  But we are looking into it – we are in the midst of a two-year research program to enable reassessment of our engineering-based understanding of the public safety consequences of vegetation on flood damage reduction projects.

Any change to current USACE vegetation management policy and standards will be based upon sound engineering and science, and will not adversely affect public safety – because that is our #1 priority.

Infrastructure, Levees , , , , ,