Peter’s Take: Stream Restoration Design Flaws Persist at Donaldson Run

Peter’s Take is a weekly opinion column. The views and opinions expressed in this column are those of the author and do not necessarily reflect the views of ARLnow.com

Despite mounting evidence that Arlington County government’s past designs for stream “restorations” are fundamentally flawed, the County persists in moving forward with these flawed designs at Donaldson Run Tributary B (“Trib B”), Gulf Branch and elsewhere.

Background

In columns last year, I outlined concerns about the County’s stream restoration designs generally and at Donaldson Run. More recently, I highlighted the County government’s failures to prioritize mature tree preservation on County-or-APS-owned property, e.g., at Ashlawn Elementary.

In December 2019, the County took the extraordinary step of issuing a press release characterizing criticisms of its stream restoration designs as “myths.” To the contrary, these County designs continue to be flawed.

County plan for Trib B stream restoration

The County’s latest stream restoration plan for Trib B would remove 86 large mature trees and plant 332 new trees (from 1-4 inches in diameter) which would have to withstand floods and deer destruction with unlikely high survival rates.

The County asserts many mature trees will simply fall over if restoration does not occur and sediment in the water flow must be arrested to protect the Potomac and Chesapeake. However, the sediment caught in step pools and low areas to moderate this flow will also contain pollutants that will stay in the local environment.

Why the County’s Trib B plan is flawed

The persistent flaws in the County’s stream restorations include:

• The stream bed may be physically restored, but the stream still will be ecologically damaged. “You can’t ask a stream to do everything an entire watershed should do,” said Margaret A. Palmer, a University of Maryland scientist who’s researched stream restoration ecology.
• Damage to the stream’s watershed cannot be rectified without taking a much more environmentally pro-active approach to the impacts of climate change, development, and loss of mature trees.
• Because the era of the “100-year” flood has been left far behind due to climate change, and rectifying the watershed will take many years, the work–and great expense–of physically restoring the stream bed may be washed away in a very short time. Therefore, the next major flood after Trib B is “restored” could ravage the stream bed, require significant rebuilding, and do so without the natural water absorption protection of the major mature trees which the County currently plans to remove.

Planting even hundreds of new trees is no subsitute for the removal of the mature ones. The relative benefits of mature trees vs. small ones are staggeringly in favor of the mature trees as regards CO2 absorption, water absorption, property value and other metrics.

Regionally, in the absence of empirical evidence on the efficacy of stream restoration projects, the issue of tree removal in pursuit of Chesapeake Bay Conservancy credits and to “remediate” stream erosion has elicited widespread recent concern.

In dense urban environments like Arlington, experts caution against the types of stream restoration techniques advocated by the County.

What can be done at Trib B

Some things can and should be done now at Trib B in view of the ravages of recent floods and the County’s lack of any meaningful maintenance of the stream. Some sewer lines may be subject to damage and should be rerouted (e.g., San Diego) or protected. Water pipes should be protected (using any of a wide variety of methods such as stacked stone walls and repairing stormwater discharge pipes) that would not require the heavy equipment the County currently proposes for the “restoration.” And, a relatively few mature trees would have their roots so exposed that they might have to be removed before they fall. CIP funds should be made available for all the above work.

Conclusion

County government is poised to repeat past mistakes by replicating them at Donaldson Run Trib B costing $1.45M for stream work alone (not infrastructure repair). Refusing to address development and land-use problems by merely adjusting stream channels to manage greater volumes of runoff won’t work against climate-change-era floods. Aggressively maintaining Trib B to handle both moderate and truly major floods, possible rerouting of water pipes out of the stream bed, and focusing greater attention on conservation of our natural resources are the keys to a cost-effective Trib B approach.

Peter Rousselot previously served as Chair of the Fiscal Affairs Advisory Commission (FAAC) to the Arlington County Board and as Co-Chair of the Advisory Council on Instruction (ACI) to the Arlington School Board. He is also a former Chair of the Arlington County Democratic Committee (ACDC) and a former member of the Central Committee of the Democratic Party of Virginia (DPVA). He currently serves as a board member of the Together Virginia PAC-a political action committee dedicated to identifying, helping and advising Democratic candidates in rural Virginia.